diff --git a/Demo/Demo.xcodeproj/project.pbxproj b/Demo/Demo.xcodeproj/project.pbxproj
index 780b3fd6..e68ec64e 100644
--- a/Demo/Demo.xcodeproj/project.pbxproj
+++ b/Demo/Demo.xcodeproj/project.pbxproj
@@ -7,6 +7,32 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		022658412238FCD600991DA2 /* TestView.xib in Resources */ = {isa = PBXBuildFile; fileRef = 022658402238FCD600991DA2 /* TestView.xib */; };
+		022658432238FD4500991DA2 /* TestView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 022658422238FD4500991DA2 /* TestView.swift */; };
+		022658452238FE0C00991DA2 /* AView.xib in Resources */ = {isa = PBXBuildFile; fileRef = 022658442238FE0C00991DA2 /* AView.xib */; };
+		022658472238FEC000991DA2 /* AView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 022658462238FEC000991DA2 /* AView.swift */; };
+		029050DF2191737E00B9681F /* TestViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 029050DE2191737E00B9681F /* TestViewController.swift */; };
+		02F4F97C224C6766009CC649 /* CustomAnimation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F97B224C6766009CC649 /* CustomAnimation.swift */; };
+		02F4F97F224C6890009CC649 /* CustomPanHandler.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F97E224C6890009CC649 /* CustomPanHandler.swift */; };
+		02F4F996224C727A009CC649 /* Stevia+Style.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F981224C7279009CC649 /* Stevia+Style.swift */; };
+		02F4F997224C727A009CC649 /* Stevia+DoubleDash.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F982224C7279009CC649 /* Stevia+DoubleDash.swift */; };
+		02F4F998224C727A009CC649 /* Stevia+GetConstraint.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F983224C7279009CC649 /* Stevia+GetConstraint.swift */; };
+		02F4F999224C727A009CC649 /* Stevia+Operators.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F984224C7279009CC649 /* Stevia+Operators.swift */; };
+		02F4F99A224C727A009CC649 /* Stevia+Center.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F985224C7279009CC649 /* Stevia+Center.swift */; };
+		02F4F99B224C727A009CC649 /* Stevia+Fill.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F986224C7279009CC649 /* Stevia+Fill.swift */; };
+		02F4F99C224C727A009CC649 /* Stevia+Position.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F987224C7279009CC649 /* Stevia+Position.swift */; };
+		02F4F99D224C727A009CC649 /* Stevia+Notifications.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F988224C7279009CC649 /* Stevia+Notifications.swift */; };
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+		02F4F99F224C727A009CC649 /* Stevia+Baselines.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F98A224C7279009CC649 /* Stevia+Baselines.swift */; };
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+		02F4F9A1224C727A009CC649 /* Stevia+Constraints.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F98C224C7279009CC649 /* Stevia+Constraints.swift */; };
+		02F4F9A2224C727A009CC649 /* Stevia+Size.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F98E224C7279009CC649 /* Stevia+Size.swift */; };
+		02F4F9A3224C727A009CC649 /* Stevia+Stacks.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F98F224C7279009CC649 /* Stevia+Stacks.swift */; };
+		02F4F9A4224C727A009CC649 /* Stevia+Percentage.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F990224C7279009CC649 /* Stevia+Percentage.swift */; };
+		02F4F9A5224C727A009CC649 /* Stevia+Equation.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F991224C7279009CC649 /* Stevia+Equation.swift */; };
+		02F4F9A6224C727A009CC649 /* Stevia+Alignment.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F992224C7279009CC649 /* Stevia+Alignment.swift */; };
+		02F4F9A7224C727A009CC649 /* Stevia+LayoutAnchors.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F993224C7279009CC649 /* Stevia+LayoutAnchors.swift */; };
+		02F4F9A9224C727A009CC649 /* Stevia+Content.swift in Sources */ = {isa = PBXBuildFile; fileRef = 02F4F995224C7279009CC649 /* Stevia+Content.swift */; };
 		22652712210F698600310344 /* TacoDialogView.xib in Resources */ = {isa = PBXBuildFile; fileRef = 86C0AB9F1D5E814600F76BD6 /* TacoDialogView.xib */; };
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 		226FA5E81F5071D0004CB2BC /* CountedMessageView.swift in Sources */ = {isa = PBXBuildFile; fileRef = 226FA5E71F5071D0004CB2BC /* CountedMessageView.swift */; };
@@ -79,6 +105,32 @@
 /* End PBXCopyFilesBuildPhase section */
 
 /* Begin PBXFileReference section */
+		022658402238FCD600991DA2 /* TestView.xib */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = file.xib; name = TestView.xib; path = ../../SwiftMessages/Resources/TestView.xib; sourceTree = "<group>"; };
+		022658422238FD4500991DA2 /* TestView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TestView.swift; sourceTree = "<group>"; };
+		022658442238FE0C00991DA2 /* AView.xib */ = {isa = PBXFileReference; lastKnownFileType = file.xib; path = AView.xib; sourceTree = "<group>"; };
+		022658462238FEC000991DA2 /* AView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AView.swift; sourceTree = "<group>"; };
+		029050DE2191737E00B9681F /* TestViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TestViewController.swift; sourceTree = "<group>"; };
+		02F4F97B224C6766009CC649 /* CustomAnimation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CustomAnimation.swift; sourceTree = "<group>"; };
+		02F4F97E224C6890009CC649 /* CustomPanHandler.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CustomPanHandler.swift; sourceTree = "<group>"; };
+		02F4F981224C7279009CC649 /* Stevia+Style.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Style.swift"; sourceTree = "<group>"; };
+		02F4F982224C7279009CC649 /* Stevia+DoubleDash.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+DoubleDash.swift"; sourceTree = "<group>"; };
+		02F4F983224C7279009CC649 /* Stevia+GetConstraint.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+GetConstraint.swift"; sourceTree = "<group>"; };
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+		02F4F986224C7279009CC649 /* Stevia+Fill.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Fill.swift"; sourceTree = "<group>"; };
+		02F4F987224C7279009CC649 /* Stevia+Position.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Position.swift"; sourceTree = "<group>"; };
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+		02F4F98B224C7279009CC649 /* Stevia+Hierarchy.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Hierarchy.swift"; sourceTree = "<group>"; };
+		02F4F98C224C7279009CC649 /* Stevia+Constraints.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Constraints.swift"; sourceTree = "<group>"; };
+		02F4F98E224C7279009CC649 /* Stevia+Size.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Size.swift"; sourceTree = "<group>"; };
+		02F4F98F224C7279009CC649 /* Stevia+Stacks.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Stacks.swift"; sourceTree = "<group>"; };
+		02F4F990224C7279009CC649 /* Stevia+Percentage.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Percentage.swift"; sourceTree = "<group>"; };
+		02F4F991224C7279009CC649 /* Stevia+Equation.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Equation.swift"; sourceTree = "<group>"; };
+		02F4F992224C7279009CC649 /* Stevia+Alignment.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Alignment.swift"; sourceTree = "<group>"; };
+		02F4F993224C7279009CC649 /* Stevia+LayoutAnchors.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+LayoutAnchors.swift"; sourceTree = "<group>"; };
+		02F4F995224C7279009CC649 /* Stevia+Content.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "Stevia+Content.swift"; sourceTree = "<group>"; };
 		226FA5E51F506993004CB2BC /* CountedViewController.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CountedViewController.swift; sourceTree = "<group>"; };
 		226FA5E71F5071D0004CB2BC /* CountedMessageView.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = CountedMessageView.swift; sourceTree = "<group>"; };
 		226FA5E91F507586004CB2BC /* Utils.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Utils.swift; sourceTree = "<group>"; };
@@ -109,6 +161,32 @@
 /* End PBXFrameworksBuildPhase section */
 
 /* Begin PBXGroup section */
+		02F4F980224C7279009CC649 /* Source */ = {
+			isa = PBXGroup;
+			children = (
+				02F4F981224C7279009CC649 /* Stevia+Style.swift */,
+				02F4F982224C7279009CC649 /* Stevia+DoubleDash.swift */,
+				02F4F983224C7279009CC649 /* Stevia+GetConstraint.swift */,
+				02F4F984224C7279009CC649 /* Stevia+Operators.swift */,
+				02F4F985224C7279009CC649 /* Stevia+Center.swift */,
+				02F4F986224C7279009CC649 /* Stevia+Fill.swift */,
+				02F4F987224C7279009CC649 /* Stevia+Position.swift */,
+				02F4F988224C7279009CC649 /* Stevia+Notifications.swift */,
+				02F4F989224C7279009CC649 /* Stevia+FlexibleMargin.swift */,
+				02F4F98A224C7279009CC649 /* Stevia+Baselines.swift */,
+				02F4F98B224C7279009CC649 /* Stevia+Hierarchy.swift */,
+				02F4F98C224C7279009CC649 /* Stevia+Constraints.swift */,
+				02F4F98E224C7279009CC649 /* Stevia+Size.swift */,
+				02F4F98F224C7279009CC649 /* Stevia+Stacks.swift */,
+				02F4F990224C7279009CC649 /* Stevia+Percentage.swift */,
+				02F4F991224C7279009CC649 /* Stevia+Equation.swift */,
+				02F4F992224C7279009CC649 /* Stevia+Alignment.swift */,
+				02F4F993224C7279009CC649 /* Stevia+LayoutAnchors.swift */,
+				02F4F995224C7279009CC649 /* Stevia+Content.swift */,
+			);
+			path = Source;
+			sourceTree = "<group>";
+		};
 		22FB323B21193A3B005C13D9 /* Products */ = {
 			isa = PBXGroup;
 			children = (
@@ -129,6 +207,7 @@
 		86AEDCD91D5D1DB70030232E = {
 			isa = PBXGroup;
 			children = (
+				02F4F980224C7279009CC649 /* Source */,
 				86AEDCE41D5D1DB70030232E /* Demo */,
 				86AEDCE31D5D1DB70030232E /* Products */,
 				6AB98897E817EE976DD72852 /* Frameworks */,
@@ -150,6 +229,8 @@
 				86AEDCE51D5D1DB70030232E /* AppDelegate.swift */,
 				86AEDCE91D5D1DB70030232E /* Main.storyboard */,
 				86AEDCE71D5D1DB70030232E /* ViewController.swift */,
+				02F4F97B224C6766009CC649 /* CustomAnimation.swift */,
+				02F4F97E224C6890009CC649 /* CustomPanHandler.swift */,
 				8642F4351D5F7F540061BDCD /* ExploreViewController.swift */,
 				226FA5E51F506993004CB2BC /* CountedViewController.swift */,
 				22F27952210D0FDE00273E7F /* ViewControllersViewController.swift */,
@@ -158,8 +239,13 @@
 				86AEDCF11D5D1DB70030232E /* Info.plist */,
 				86C0ABA11D5E816600F76BD6 /* TacoDialogView.swift */,
 				86C0AB9F1D5E814600F76BD6 /* TacoDialogView.xib */,
+				022658402238FCD600991DA2 /* TestView.xib */,
+				022658422238FD4500991DA2 /* TestView.swift */,
+				022658442238FE0C00991DA2 /* AView.xib */,
+				022658462238FEC000991DA2 /* AView.swift */,
 				226FA5E71F5071D0004CB2BC /* CountedMessageView.swift */,
 				226FA5E91F507586004CB2BC /* Utils.swift */,
+				029050DE2191737E00B9681F /* TestViewController.swift */,
 			);
 			path = Demo;
 			sourceTree = "<group>";
@@ -200,7 +286,7 @@
 				TargetAttributes = {
 					86AEDCE11D5D1DB70030232E = {
 						CreatedOnToolsVersion = 7.3.1;
-						DevelopmentTeam = 38R82CD868;
+						DevelopmentTeam = 89YHB42JY7;
 						LastSwiftMigration = 1000;
 					};
 				};
@@ -210,6 +296,7 @@
 			developmentRegion = English;
 			hasScannedForEncodings = 0;
 			knownRegions = (
+				English,
 				en,
 				Base,
 			);
@@ -251,8 +338,10 @@
 			isa = PBXResourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				022658452238FE0C00991DA2 /* AView.xib in Resources */,
 				86AEDCF01D5D1DB70030232E /* LaunchScreen.storyboard in Resources */,
 				22652712210F698600310344 /* TacoDialogView.xib in Resources */,
+				022658412238FCD600991DA2 /* TestView.xib in Resources */,
 				86AEDCED1D5D1DB70030232E /* Assets.xcassets in Resources */,
 				86AEDCEB1D5D1DB70030232E /* Main.storyboard in Resources */,
 			);
@@ -265,14 +354,38 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				02F4F9A7224C727A009CC649 /* Stevia+LayoutAnchors.swift in Sources */,
+				02F4F9A9224C727A009CC649 /* Stevia+Content.swift in Sources */,
+				02F4F99A224C727A009CC649 /* Stevia+Center.swift in Sources */,
+				02F4F99D224C727A009CC649 /* Stevia+Notifications.swift in Sources */,
 				8642F4361D5F7F540061BDCD /* ExploreViewController.swift in Sources */,
+				02F4F9A6224C727A009CC649 /* Stevia+Alignment.swift in Sources */,
+				02F4F998224C727A009CC649 /* Stevia+GetConstraint.swift in Sources */,
+				02F4F997224C727A009CC649 /* Stevia+DoubleDash.swift in Sources */,
+				022658472238FEC000991DA2 /* AView.swift in Sources */,
+				02F4F99B224C727A009CC649 /* Stevia+Fill.swift in Sources */,
 				226FA5E81F5071D0004CB2BC /* CountedMessageView.swift in Sources */,
+				02F4F996224C727A009CC649 /* Stevia+Style.swift in Sources */,
 				86AEDCE81D5D1DB70030232E /* ViewController.swift in Sources */,
+				02F4F9A2224C727A009CC649 /* Stevia+Size.swift in Sources */,
+				02F4F9A4224C727A009CC649 /* Stevia+Percentage.swift in Sources */,
+				02F4F999224C727A009CC649 /* Stevia+Operators.swift in Sources */,
+				02F4F9A5224C727A009CC649 /* Stevia+Equation.swift in Sources */,
 				226FA5EA1F507586004CB2BC /* Utils.swift in Sources */,
+				02F4F99E224C727A009CC649 /* Stevia+FlexibleMargin.swift in Sources */,
+				02F4F99F224C727A009CC649 /* Stevia+Baselines.swift in Sources */,
+				02F4F97F224C6890009CC649 /* CustomPanHandler.swift in Sources */,
+				02F4F9A0224C727A009CC649 /* Stevia+Hierarchy.swift in Sources */,
+				02F4F99C224C727A009CC649 /* Stevia+Position.swift in Sources */,
 				86AEDCE61D5D1DB70030232E /* AppDelegate.swift in Sources */,
+				02F4F9A3224C727A009CC649 /* Stevia+Stacks.swift in Sources */,
 				226FA5E61F506993004CB2BC /* CountedViewController.swift in Sources */,
+				022658432238FD4500991DA2 /* TestView.swift in Sources */,
+				02F4F9A1224C727A009CC649 /* Stevia+Constraints.swift in Sources */,
 				86C0ABA21D5E816600F76BD6 /* TacoDialogView.swift in Sources */,
+				029050DF2191737E00B9681F /* TestViewController.swift in Sources */,
 				22F27953210D0FDE00273E7F /* ViewControllersViewController.swift in Sources */,
+				02F4F97C224C6766009CC649 /* CustomAnimation.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
@@ -423,7 +536,7 @@
 				ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES = YES;
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				CODE_SIGN_IDENTITY = "iPhone Developer";
-				DEVELOPMENT_TEAM = 38R82CD868;
+				DEVELOPMENT_TEAM = 89YHB42JY7;
 				INFOPLIST_FILE = Demo/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = it.swiftkick.Demo;
@@ -438,7 +551,7 @@
 				ALWAYS_EMBED_SWIFT_STANDARD_LIBRARIES = YES;
 				ASSETCATALOG_COMPILER_APPICON_NAME = AppIcon;
 				CODE_SIGN_IDENTITY = "iPhone Developer";
-				DEVELOPMENT_TEAM = 38R82CD868;
+				DEVELOPMENT_TEAM = 89YHB42JY7;
 				INFOPLIST_FILE = Demo/Info.plist;
 				LD_RUNPATH_SEARCH_PATHS = "$(inherited) @executable_path/Frameworks";
 				PRODUCT_BUNDLE_IDENTIFIER = it.swiftkick.Demo;
diff --git a/Demo/Demo.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist b/Demo/Demo.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
new file mode 100644
index 00000000..18d98100
--- /dev/null
+++ b/Demo/Demo.xcworkspace/xcshareddata/IDEWorkspaceChecks.plist
@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+<dict>
+	<key>IDEDidComputeMac32BitWarning</key>
+	<true/>
+</dict>
+</plist>
diff --git a/Demo/Demo/AView.swift b/Demo/Demo/AView.swift
new file mode 100644
index 00000000..14a9994e
--- /dev/null
+++ b/Demo/Demo/AView.swift
@@ -0,0 +1,20 @@
+//
+//  AView.swift
+//  Demo
+//
+//  Created by Hanguang on 2019/3/13.
+//  Copyright © 2019 SwiftKick Mobile. All rights reserved.
+//
+
+import UIKit
+import SwiftMessages
+
+class AView: MessageView {
+    var position: CGPoint = .zero {
+        didSet {
+            var frame = backgroundView.frame
+            frame.origin = position
+            backgroundView.frame = frame
+        }
+    }
+}
diff --git a/Demo/Demo/AView.xib b/Demo/Demo/AView.xib
new file mode 100644
index 00000000..08d1536b
--- /dev/null
+++ b/Demo/Demo/AView.xib
@@ -0,0 +1,42 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES">
+    <device id="retina4_7" orientation="portrait">
+        <adaptation id="fullscreen"/>
+    </device>
+    <dependencies>
+        <deployment identifier="iOS"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14490.70"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <objects>
+        <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>
+        <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
+        <view contentMode="scaleToFill" id="iN0-l3-epB" customClass="AView" customModule="Demo" customModuleProvider="target">
+            <rect key="frame" x="0.0" y="0.0" width="200" height="150"/>
+            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+            <subviews>
+                <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="N1R-0e-7ta" userLabel="backgroundView" customClass="CornerRoundingView" customModule="SwiftMessages">
+                    <rect key="frame" x="0.0" y="0.0" width="200" height="150"/>
+                    <color key="backgroundColor" white="1" alpha="1" colorSpace="custom" customColorSpace="genericGamma22GrayColorSpace"/>
+                    <userDefinedRuntimeAttributes>
+                        <userDefinedRuntimeAttribute type="number" keyPath="cornerRadius">
+                            <real key="value" value="15"/>
+                        </userDefinedRuntimeAttribute>
+                    </userDefinedRuntimeAttributes>
+                </view>
+            </subviews>
+            <constraints>
+                <constraint firstAttribute="trailing" secondItem="N1R-0e-7ta" secondAttribute="trailing" id="Cre-i0-ysc"/>
+                <constraint firstItem="N1R-0e-7ta" firstAttribute="leading" secondItem="iN0-l3-epB" secondAttribute="leading" id="ZFL-u5-2cI"/>
+                <constraint firstAttribute="bottom" secondItem="N1R-0e-7ta" secondAttribute="bottom" id="qel-FM-rWP"/>
+                <constraint firstItem="N1R-0e-7ta" firstAttribute="top" secondItem="iN0-l3-epB" secondAttribute="top" id="zch-If-UcI"/>
+            </constraints>
+            <nil key="simulatedTopBarMetrics"/>
+            <nil key="simulatedBottomBarMetrics"/>
+            <freeformSimulatedSizeMetrics key="simulatedDestinationMetrics"/>
+            <connections>
+                <outlet property="backgroundView" destination="N1R-0e-7ta" id="bNM-09-WZN"/>
+            </connections>
+        </view>
+    </objects>
+</document>
diff --git a/Demo/Demo/Base.lproj/Main.storyboard b/Demo/Demo/Base.lproj/Main.storyboard
index 12449d96..93e7be66 100644
--- a/Demo/Demo/Base.lproj/Main.storyboard
+++ b/Demo/Demo/Base.lproj/Main.storyboard
@@ -1,13 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14113" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES" initialViewController="JQZ-C5-7mw">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.Storyboard.XIB" version="3.0" toolsVersion="14490.70" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES" initialViewController="JQZ-C5-7mw">
     <device id="retina4_7" orientation="portrait">
         <adaptation id="fullscreen"/>
     </device>
     <dependencies>
         <deployment identifier="iOS"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14088"/>
-        <capability name="Alignment constraints with different attributes" minToolsVersion="5.1"/>
-        <capability name="Constraints to layout margins" minToolsVersion="6.0"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14490.49"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <scenes>
@@ -220,7 +218,32 @@
                             <outlet property="delegate" destination="vur-BZ-g1e" id="P2z-vo-Vm2"/>
                         </connections>
                     </tableView>
-                    <navigationItem key="navigationItem" title="Demo" id="2KJ-2Z-WHF"/>
+                    <toolbarItems>
+                        <barButtonItem systemItem="reply" id="voE-tL-PXY">
+                            <connections>
+                                <action selector="showPopover:event:" destination="vur-BZ-g1e" id="EHM-uP-3bh"/>
+                            </connections>
+                        </barButtonItem>
+                        <barButtonItem style="plain" systemItem="flexibleSpace" id="O6V-Nu-8XW"/>
+                        <barButtonItem systemItem="action" id="ccf-6D-xio">
+                            <connections>
+                                <action selector="showPopover:event:" destination="vur-BZ-g1e" id="j4e-Th-dEe"/>
+                            </connections>
+                        </barButtonItem>
+                    </toolbarItems>
+                    <navigationItem key="navigationItem" title="Demo" id="2KJ-2Z-WHF">
+                        <barButtonItem key="leftBarButtonItem" systemItem="done" id="g2r-w7-7te">
+                            <connections>
+                                <action selector="showPopover:event:" destination="vur-BZ-g1e" id="k3T-tp-WIk"/>
+                            </connections>
+                        </barButtonItem>
+                        <barButtonItem key="rightBarButtonItem" systemItem="camera" id="hxG-ru-G1V">
+                            <connections>
+                                <action selector="showPopover:event:" destination="vur-BZ-g1e" id="TkF-bq-JcA"/>
+                            </connections>
+                        </barButtonItem>
+                    </navigationItem>
+                    <simulatedToolbarMetrics key="simulatedBottomBarMetrics"/>
                 </tableViewController>
                 <placeholder placeholderIdentifier="IBFirstResponder" id="L1V-tt-hkn" userLabel="First Responder" sceneMemberID="firstResponder"/>
             </objects>
@@ -833,10 +856,10 @@
                         <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
                         <subviews>
                             <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" distribution="fillEqually" spacing="10" translatesAutoresizingMaskIntoConstraints="NO" id="mGe-El-haJ">
-                                <rect key="frame" x="46" y="104" width="283" height="474"/>
+                                <rect key="frame" x="46" y="104" width="283" height="430"/>
                                 <subviews>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="DrN-Ei-Pg7">
-                                        <rect key="frame" x="0.0" y="0.0" width="283" height="59"/>
+                                        <rect key="frame" x="0.0" y="0.0" width="283" height="53"/>
                                         <color key="backgroundColor" red="0.16470588235294117" green="0.6588235294117647" blue="0.98039215686274506" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Top Message"/>
@@ -850,7 +873,7 @@
                                         </connections>
                                     </button>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="GeC-SP-rSC">
-                                        <rect key="frame" x="0.0" y="69" width="283" height="59.5"/>
+                                        <rect key="frame" x="0.0" y="63" width="283" height="52.5"/>
                                         <color key="backgroundColor" red="0.1647058824" green="0.6588235294" blue="0.98039215690000003" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Bottom Message"/>
@@ -864,7 +887,7 @@
                                         </connections>
                                     </button>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="DGn-eY-EEX">
-                                        <rect key="frame" x="0.0" y="138.5" width="283" height="59"/>
+                                        <rect key="frame" x="0.0" y="125.5" width="283" height="53"/>
                                         <color key="backgroundColor" red="0.26627604170000002" green="0.76907009550000005" blue="0.32259114579999998" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Top Card"/>
@@ -878,7 +901,7 @@
                                         </connections>
                                     </button>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="ZQs-MK-vK3">
-                                        <rect key="frame" x="0.0" y="207.5" width="283" height="59"/>
+                                        <rect key="frame" x="0.0" y="188.5" width="283" height="53"/>
                                         <color key="backgroundColor" red="0.26627604170000002" green="0.76907009550000005" blue="0.32259114579999998" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Bottom Card"/>
@@ -892,7 +915,7 @@
                                         </connections>
                                     </button>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="kux-aE-Bdv" userLabel="Top Tab">
-                                        <rect key="frame" x="0.0" y="276.5" width="283" height="59"/>
+                                        <rect key="frame" x="0.0" y="251.5" width="283" height="53"/>
                                         <color key="backgroundColor" red="0.80000000000000004" green="0.015686274510000067" blue="0.62082127703967116" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Top Tab"/>
@@ -906,7 +929,7 @@
                                         </connections>
                                     </button>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="dMQ-xF-RwV" userLabel="Bottom Tab">
-                                        <rect key="frame" x="0.0" y="345.5" width="283" height="59.5"/>
+                                        <rect key="frame" x="0.0" y="314.5" width="283" height="52.5"/>
                                         <color key="backgroundColor" red="0.80000000000000004" green="0.015686274510000001" blue="0.620821277" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Bottom Tab"/>
@@ -920,7 +943,7 @@
                                         </connections>
                                     </button>
                                     <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="CDi-Gu-bE2" userLabel="Centered">
-                                        <rect key="frame" x="0.0" y="415" width="283" height="59"/>
+                                        <rect key="frame" x="0.0" y="377" width="283" height="53"/>
                                         <color key="backgroundColor" red="1" green="0.46653546191345963" blue="0.015686274510000042" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                         <fontDescription key="fontDescription" type="boldSystem" pointSize="18"/>
                                         <state key="normal" title="Centered"/>
diff --git a/Demo/Demo/CustomAnimation.swift b/Demo/Demo/CustomAnimation.swift
new file mode 100644
index 00000000..5e814f18
--- /dev/null
+++ b/Demo/Demo/CustomAnimation.swift
@@ -0,0 +1,430 @@
+//
+//  CustomAnimation.swift
+//  Demo
+//
+//  Created by Hanguang on 2019/3/28.
+//  Copyright © 2019 SwiftKick Mobile. All rights reserved.
+//
+
+import UIKit
+import SwiftMessages
+
+public class CustomAnimation: NSObject, Animator {
+    enum ArrowDirection {
+        case up
+        case down
+    }
+    
+    public var margin: CGFloat = 4
+    public var arrowWidth: CGFloat = 8
+    public var arrowHeight: CGFloat = 10
+    
+    weak public var delegate: AnimationDelegate?
+    weak var messageView: UIView?
+    weak var containerView: UIView?
+    var context: AnimationContext?
+    
+    private lazy var menuView: UIView = {
+        return UIView()
+    }()
+    private lazy var backgroundLayer: CAShapeLayer = {
+        let layer = CAShapeLayer()
+        return layer
+    }()
+    private var arrowDirection: ArrowDirection = .up
+    var containerSize: CGSize {
+        return containerView?.frame.size ?? .zero
+    }
+    var cornerRadius: CGFloat = 15.0
+    var popoverFrame: CGRect?
+    var popoverView: UIView?
+    var fillColor: CGColor? = UIColor.white.cgColor
+    var strokeColor: CGColor?
+    var lineWidth: CGFloat = 0
+    
+    public override init() {}
+    
+    init(delegate: AnimationDelegate) {
+        self.delegate = delegate
+    }
+    
+    public func show(context: AnimationContext, completion: @escaping AnimationCompletion) {
+        NotificationCenter.default.addObserver(self, selector: #selector(adjustMargins), name: UIDevice.orientationDidChangeNotification, object: nil)
+        install(context: context)
+        showAnimation(context: context, completion: completion)
+    }
+    
+    public func hide(context: AnimationContext, completion: @escaping AnimationCompletion) {
+        NotificationCenter.default.removeObserver(self)
+        let view = menuView
+        self.context = context
+        CATransaction.begin()
+        CATransaction.setCompletionBlock {
+            view.alpha = 1
+            view.transform = CGAffineTransform.identity
+            completion(true)
+        }
+        UIView.animate(withDuration: hideDuration!, delay: 0, options: [.beginFromCurrentState, .curveEaseIn, .allowUserInteraction], animations: {
+            view.transform = CGAffineTransform(scaleX: 0.8, y: 0.8)
+        }, completion: nil)
+        UIView.animate(withDuration: hideDuration!, delay: 0, options: [.beginFromCurrentState, .curveEaseIn, .allowUserInteraction], animations: {
+            view.alpha = 0
+        }, completion: nil)
+        CATransaction.commit()
+    }
+    
+    public var showDuration: TimeInterval? { return 0.5  }
+    public var hideDuration: TimeInterval? { return 0.15  }
+    
+    func install(context: AnimationContext) {
+        let view = context.messageView
+        let container = context.containerView
+        
+        if let view = view as? MessageView,
+            let bg = view.backgroundView as? CornerRoundingView {
+            cornerRadius = bg.cornerRadius
+        }
+        
+        menuView.bounds = view.bounds
+        messageView = context.messageView
+        containerView = container
+        self.context = context
+        
+        // add view
+        container.sv(
+            menuView.sv(view)
+        )
+        
+        // position
+        let values = preparedValues()
+        menuView.frame = values.menuFrame
+        arrowDirection = values.arrowDirection
+        
+        // draw background layer
+        installBackgroundLayer(menuView, point: values.arrowPoint)
+        
+        // install anchor
+        let offset = installAnchorPoint(menuView, point: values.arrowPoint)
+        
+        container.layout(
+            offset.y,
+            |-offset.x-menuView
+        )
+        
+        // size
+        menuView.width(values.menuFrame.width)
+        menuView.height(values.menuFrame.height)
+        view.fillHorizontally()
+        if arrowDirection == .up {
+            view.top(arrowHeight)
+            view.bottom(0)
+        } else {
+            view.bottom(arrowHeight)
+            view.top(0)
+        }
+        
+        container.layoutIfNeeded()
+        adjustMargins()
+        container.layoutIfNeeded()
+    }
+    
+    @objc public func adjustMargins() {
+        guard let adjustable = menuView as? MarginAdjustable & UIView,
+            let context = context else { return }
+        adjustable.preservesSuperviewLayoutMargins = false
+        if #available(iOS 11, *) {
+            adjustable.insetsLayoutMarginsFromSafeArea = false
+        }
+        adjustable.layoutMargins = adjustable.defaultMarginAdjustment(context: context)
+    }
+    
+    func showAnimation(context: AnimationContext, completion: @escaping AnimationCompletion) {
+        let view = menuView
+        view.alpha = 0.25
+        view.transform = CGAffineTransform(scaleX: 0.1, y: 0.1)
+        CATransaction.begin()
+        CATransaction.setCompletionBlock {
+            completion(true)
+        }
+        UIView.animate(withDuration: showDuration!, delay: 0, usingSpringWithDamping: 0.6, initialSpringVelocity: 0, options: [.beginFromCurrentState, .curveLinear, .allowUserInteraction], animations: {
+            view.transform = CGAffineTransform.identity
+        }, completion: nil)
+        UIView.animate(withDuration: 0.3 * showDuration!, delay: 0, options: [.beginFromCurrentState, .curveLinear, .allowUserInteraction], animations: {
+            view.alpha = 1
+        }, completion: nil)
+        CATransaction.commit()
+    }
+}
+
+extension CustomAnimation {
+    func preparedValues() -> (arrowPoint: CGPoint,
+        arrowDirection: ArrowDirection,
+        menuFrame: CGRect) {
+            var senderRect: CGRect = .zero
+            var arrowDirection: ArrowDirection = .up
+            var arrowPoint: CGPoint = .zero
+            var menuOffsetX: CGFloat = 0
+            var menuFrame: CGRect = menuView.frame
+            
+            // sender rect
+            if let frame = popoverFrame {
+                senderRect = frame
+            } else if let view = popoverView,
+                let superView = view.superview {
+                senderRect = superView.convert(view.frame, to: containerView)
+            }
+            senderRect.origin.y = min(containerSize.height, senderRect.origin.y)
+            
+            // arrow direction
+            if senderRect.midY < containerSize.height/2 {
+                arrowDirection = .up
+            } else {
+                arrowDirection = .down
+            }
+            
+            // arrow point
+            arrowPoint = CGPoint(x: senderRect.midX, y: 0)
+            let menuSize = menuView.frame.size
+            let menuCenterX = menuSize.width/2 + margin
+            if senderRect.midY < containerSize.height/2 {
+                arrowPoint.y = 0
+            } else {
+                arrowPoint.y = menuSize.height+arrowHeight
+            }
+            if arrowPoint.x+menuCenterX > containerSize.width {
+                arrowPoint.x = min(
+                    arrowPoint.x-(containerSize.width-menuSize.width-margin),
+                    menuSize.width-arrowWidth-margin
+                )
+            } else if arrowPoint.x-menuCenterX < 0 {
+                arrowPoint.x = max(
+                    cornerRadius+arrowWidth,
+                    arrowPoint.x-margin
+                )
+            } else {
+                arrowPoint.x = menuSize.width/2
+            }
+            
+            // menu offset x
+            var senderCenterX = senderRect.midX
+            if senderRect.midX+menuCenterX > containerSize.width {
+                senderCenterX = min(
+                    senderCenterX-(containerSize.width-menuSize.width-margin),
+                    menuSize.width-arrowWidth-margin
+                )
+                menuOffsetX = containerSize.width-menuSize.width-margin
+            } else if senderCenterX-menuCenterX < 0 {
+                senderCenterX = max(
+                    cornerRadius+arrowWidth,
+                    senderCenterX-margin
+                )
+                menuOffsetX = margin
+            } else {
+                senderCenterX = menuSize.width/2
+                menuOffsetX = senderRect.midX - menuSize.width/2
+            }
+            
+            // menu frame
+            if arrowDirection == .up {
+                menuFrame = CGRect(
+                    x: menuOffsetX,
+                    y: senderRect.maxY,
+                    width: menuSize.width,
+                    height: menuSize.height+arrowHeight
+                )
+                if (menuFrame.maxY > containerSize.height) {
+                    menuFrame = CGRect(
+                        x: menuOffsetX,
+                        y: senderRect.maxY,
+                        width: menuSize.width,
+                        height: containerSize.height-menuFrame.origin.y-margin
+                    )
+                }
+            } else {
+                menuFrame = CGRect(
+                    x: menuOffsetX,
+                    y: senderRect.origin.y-menuSize.height-arrowHeight,
+                    width: menuSize.width,
+                    height: menuSize.height+arrowHeight
+                )
+                if menuFrame.origin.y < 0 {
+                    menuFrame = CGRect(
+                        x: menuOffsetX,
+                        y: margin,
+                        width: menuSize.width,
+                        height: senderRect.origin.y-margin
+                    )
+                }
+            }
+            
+            return (arrowPoint, arrowDirection, menuFrame)
+    }
+    
+    func installBackgroundLayer(_ view: UIView, point: CGPoint) {
+        backgroundLayer.removeFromSuperlayer()
+        backgroundLayer.path = backgroundPath(view, arrowPoint: point).cgPath
+        backgroundLayer.fillColor = fillColor
+        backgroundLayer.strokeColor = strokeColor
+        backgroundLayer.lineWidth = lineWidth
+        
+        // read shadow from message view
+        if let messageView = messageView as? MessageView {
+            backgroundLayer.shadowColor = messageView.layer.shadowColor
+            backgroundLayer.shadowOffset = messageView.layer.shadowOffset
+            backgroundLayer.shadowOpacity = messageView.layer.shadowOpacity
+            backgroundLayer.masksToBounds = messageView.layer.masksToBounds
+            backgroundLayer.shouldRasterize = true
+            backgroundLayer.rasterizationScale = UIScreen.main.scale
+            messageView.layer.shadowOpacity = 0.0
+        }
+        
+        view.layer.insertSublayer(backgroundLayer, at: 0)
+    }
+    
+    func backgroundPath(_ view: UIView, arrowPoint: CGPoint) -> UIBezierPath {
+        let viewWidth = view.frame.width
+        let viewHeight = view.frame.height
+        let radius: CGFloat = cornerRadius
+        
+        let path = UIBezierPath()
+        path.lineJoinStyle = .round
+        path.lineCapStyle = .round
+        
+        if arrowDirection == .up {
+            path.move(to: CGPoint(
+                x: arrowPoint.x-arrowWidth,
+                y: arrowHeight)
+            )
+            path.addLine(to: CGPoint(x: arrowPoint.x, y: 0))
+            path.addLine(to: CGPoint(
+                x: arrowPoint.x+arrowWidth,
+                y: arrowHeight)
+            )
+            path.addLine(to: CGPoint(
+                x: viewWidth-radius,
+                y: arrowHeight)
+            )
+            path.addArc(
+                withCenter: CGPoint(
+                    x: viewWidth-radius,
+                    y: arrowHeight+radius
+                ),
+                radius: radius,
+                startAngle: .pi/2*3,
+                endAngle: 0,
+                clockwise: true
+            )
+            path.addLine(to: CGPoint(x: viewWidth, y: viewHeight-radius))
+            path.addArc(
+                withCenter: CGPoint(
+                    x: viewWidth-radius,
+                    y: viewHeight-radius),
+                radius: radius,
+                startAngle: 0,
+                endAngle: .pi/2,
+                clockwise: true
+            )
+            path.addLine(to: CGPoint(x: radius, y: viewHeight))
+            path.addArc(
+                withCenter: CGPoint(
+                    x: radius,
+                    y: viewHeight-radius),
+                radius: radius,
+                startAngle: .pi / 2,
+                endAngle: .pi,
+                clockwise: true
+            )
+            path.addLine(to: CGPoint(x: 0, y: arrowHeight+radius))
+            path.addArc(
+                withCenter: CGPoint(x: radius, y: arrowHeight+radius),
+                radius: radius,
+                startAngle: .pi,
+                endAngle: .pi/2*3,
+                clockwise: true
+            )
+            path.close()
+        } else {
+            path.move(to: CGPoint(
+                x: arrowPoint.x-arrowWidth,
+                y: viewHeight-arrowHeight)
+            )
+            path.addLine(to: CGPoint(x: arrowPoint.x, y: viewHeight))
+            path.addLine(to: CGPoint(
+                x: arrowPoint.x+arrowWidth,
+                y: viewHeight-arrowHeight)
+            )
+            path.addLine(to: CGPoint(
+                x: viewWidth-radius,
+                y: viewHeight-arrowHeight)
+            )
+            path.addArc(
+                withCenter: CGPoint(
+                    x: viewWidth-radius,
+                    y: viewHeight-arrowHeight-radius),
+                radius: radius,
+                startAngle: .pi/2,
+                endAngle: 0,
+                clockwise: false
+            )
+            path.addLine(to: CGPoint(x: viewWidth, y: radius))
+            path.addArc(
+                withCenter: CGPoint(x: viewWidth - radius, y: radius),
+                radius: radius,
+                startAngle: 0,
+                endAngle: .pi/2*3,
+                clockwise: false
+            )
+            path.addLine(to: CGPoint(x: radius, y: 0))
+            path.addArc(
+                withCenter: CGPoint(x: radius, y: radius),
+                radius: radius,
+                startAngle: .pi/2*3,
+                endAngle: .pi,
+                clockwise: false
+            )
+            path.addLine(to: CGPoint(
+                x: 0,
+                y: viewHeight-arrowHeight-radius)
+            )
+            path.addArc(
+                withCenter: CGPoint(
+                    x: radius,
+                    y: viewHeight-arrowHeight-radius),
+                radius: radius,
+                startAngle: .pi,
+                endAngle: .pi/2,
+                clockwise: false
+            )
+            path.close()
+        }
+        return path
+    }
+    
+    func installAnchorPoint(_ view: UIView, point: CGPoint) -> CGPoint {
+        var anchorPoint = CGPoint(x: point.x/view.frame.width, y: 0)
+        if arrowDirection == .down {
+            anchorPoint = CGPoint(x: point.x/view.frame.width, y: 1)
+        }
+        
+        var newPoint = CGPoint(
+            x: view.bounds.width*anchorPoint.x,
+            y: view.bounds.height*anchorPoint.y
+        )
+        
+        var oldPoint = CGPoint(
+            x: view.bounds.width*view.layer.anchorPoint.x,
+            y: view.bounds.height*view.layer.anchorPoint.y
+        )
+        
+        newPoint = newPoint.applying(view.transform)
+        oldPoint = oldPoint.applying(view.transform)
+        
+        let offsetX = view.frame.minX
+        let offsetY = view.frame.minY
+        let newOffsetX = offsetX + view.frame.width * (anchorPoint.x-view.layer.anchorPoint.x)
+        let newOffsetY = offsetY + view.frame.height * (anchorPoint.y-view.layer.anchorPoint.y)
+        
+        view.layer.anchorPoint = anchorPoint
+        return CGPoint(x: newOffsetX, y: newOffsetY)
+    }
+}
diff --git a/Demo/Demo/CustomPanHandler.swift b/Demo/Demo/CustomPanHandler.swift
new file mode 100644
index 00000000..388a35bd
--- /dev/null
+++ b/Demo/Demo/CustomPanHandler.swift
@@ -0,0 +1,177 @@
+//
+//  CustomPanHandler.swift
+//  Demo
+//
+//  Created by Hanguang on 2019/3/28.
+//  Copyright © 2019 SwiftKick Mobile. All rights reserved.
+//
+
+import UIKit
+import SwiftMessages
+
+open class CustomPanHandler {
+    
+    public var hideDelay: TimeInterval = 0.2
+    
+    public struct MotionSnapshot {
+        var angle: CGFloat
+        var time: CFAbsoluteTime
+    }
+    
+    public final class State {
+        
+        weak var messageView: UIView?
+        weak var containerView: UIView?
+        var dynamicAnimator: UIDynamicAnimator
+        var itemBehavior: UIDynamicItemBehavior
+        var attachmentBehavior: UIAttachmentBehavior? {
+            didSet {
+                if let oldValue = oldValue {
+                    dynamicAnimator.removeBehavior(oldValue)
+                }
+                if let attachmentBehavior = attachmentBehavior {
+                    dynamicAnimator.addBehavior(attachmentBehavior)
+                    addSnapshot()
+                }
+            }
+        }
+        var snapshots: [MotionSnapshot] = []
+        
+        public init(messageView: UIView, containerView: UIView) {
+            self.messageView = messageView
+            self.containerView = containerView
+            let dynamicAnimator = UIDynamicAnimator(referenceView: containerView)
+            let itemBehavior = UIDynamicItemBehavior(items: [messageView])
+            itemBehavior.allowsRotation = true
+            dynamicAnimator.addBehavior(itemBehavior)
+            self.itemBehavior = itemBehavior
+            self.dynamicAnimator = dynamicAnimator
+        }
+        
+        func update(attachmentAnchorPoint anchorPoint: CGPoint) {
+            addSnapshot()
+            attachmentBehavior?.anchorPoint = anchorPoint
+        }
+        
+        func addSnapshot() {
+            let angle = messageView?.angle ?? snapshots.last?.angle ?? 0
+            let time = CFAbsoluteTimeGetCurrent()
+            snapshots.append(MotionSnapshot(angle: angle, time: time))
+        }
+        
+        public func stop() {
+            guard let messageView = messageView else {
+                dynamicAnimator.removeAllBehaviors()
+                return
+            }
+            let center = messageView.center
+            let transform = messageView.transform
+            dynamicAnimator.removeAllBehaviors()
+            messageView.center = center
+            messageView.transform = transform
+        }
+        
+        public var angularVelocity: CGFloat {
+            guard let last = snapshots.last else { return 0 }
+            for previous in snapshots.reversed() {
+                // Ignore snapshots where the angle or time hasn't changed to avoid degenerate cases.
+                if previous.angle != last.angle && previous.time != last.time {
+                    return (last.angle - previous.angle) / CGFloat(last.time - previous.time)
+                }
+            }
+            return 0
+        }
+    }
+    
+    weak var animator: Animator?
+    weak var messageView: UIView?
+    weak var containerView: UIView?
+    private(set) public var state: State?
+    private(set) public var isOffScreen = false
+    private var restingCenter: CGPoint?
+    
+    public init() {}
+    
+    public private(set) lazy var pan: UIPanGestureRecognizer = {
+        let pan = UIPanGestureRecognizer()
+        pan.addTarget(self, action: #selector(pan(_:)))
+        return pan
+    }()
+    
+    func configure(context: AnimationContext, animator: Animator) {
+        if let oldView = (messageView as? BackgroundViewable)?.backgroundView ?? messageView {
+            oldView.removeGestureRecognizer(pan)
+        }
+        messageView = context.messageView
+        let view = (messageView as? BackgroundViewable)?.backgroundView ?? messageView
+        view?.addGestureRecognizer(pan)
+        containerView = context.containerView
+        self.animator = animator
+    }
+    
+    @objc func pan(_ pan: UIPanGestureRecognizer) {
+        guard let messageView = messageView, let containerView = containerView, let animator = animator else { return }
+        let anchorPoint = pan.location(in: containerView)
+        switch pan.state {
+        case .began:
+            animator.delegate?.panStarted(animator: animator)
+            let state = State(messageView: messageView, containerView: containerView)
+            self.state = state
+            let center = messageView.center
+            restingCenter = center
+            let offset = UIOffset(horizontal: anchorPoint.x - center.x, vertical: anchorPoint.y - center.y)
+            let attachmentBehavior = UIAttachmentBehavior(item: messageView, offsetFromCenter: offset, attachedToAnchor: anchorPoint)
+            state.attachmentBehavior = attachmentBehavior
+            state.itemBehavior.action = { [weak self, weak messageView, weak containerView] in
+                guard let self = self, !self.isOffScreen, let messageView = messageView, let containerView = containerView, let animator = self.animator else { return }
+                let view = (messageView as? BackgroundViewable)?.backgroundView ?? messageView
+                let frame = containerView.convert(view.bounds, from: view)
+                if !containerView.bounds.intersects(frame) {
+                    self.isOffScreen = true
+                    DispatchQueue.main.asyncAfter(deadline: .now() + self.hideDelay) {
+                        animator.delegate?.hide(animator: animator)
+                    }
+                }
+            }
+        case .changed:
+            guard let state = state else { return }
+            state.update(attachmentAnchorPoint: anchorPoint)
+        case .ended, .cancelled:
+            guard let state = state else { return }
+            state.update(attachmentAnchorPoint: anchorPoint)
+            let velocity = pan.velocity(in: containerView)
+            let angularVelocity = state.angularVelocity
+            let speed = sqrt(pow(velocity.x, 2) + pow(velocity.y, 2))
+            // The multiplier on angular velocity was determined by hand-tuning
+            let energy = sqrt(pow(speed, 2) + pow(angularVelocity * 75, 2))
+            if energy > 200 && speed > 600 {
+                // Limit the speed and angular velocity to reasonable values
+                let speedScale = speed > 0 ? min(1, 1800 / speed) : 1
+                let escapeVelocity = CGPoint(x: velocity.x * speedScale, y: velocity.y * speedScale)
+                let angularSpeedScale = min(1, 10 / abs(angularVelocity))
+                let escapeAngularVelocity = angularVelocity * angularSpeedScale
+                state.itemBehavior.addLinearVelocity(escapeVelocity, for: messageView)
+                state.itemBehavior.addAngularVelocity(escapeAngularVelocity, for: messageView)
+                state.attachmentBehavior = nil
+            } else {
+                state.stop()
+                self.state = nil
+                animator.delegate?.panEnded(animator: animator)
+                UIView.animate(withDuration: 0.5, delay: 0, usingSpringWithDamping: 0.65, initialSpringVelocity: 0, options: .beginFromCurrentState, animations: {
+                    messageView.center = self.restingCenter ?? CGPoint(x: containerView.bounds.width / 2, y: containerView.bounds.height / 2)
+                    messageView.transform = CGAffineTransform.identity
+                }, completion: nil)
+            }
+        default:
+            break
+        }
+    }
+}
+
+extension UIView {
+    var angle: CGFloat {
+        // http://stackoverflow.com/a/2051861/1271826
+        return atan2(transform.b, transform.a)
+    }
+}
+
diff --git a/Demo/Demo/TacoDialogView.xib b/Demo/Demo/TacoDialogView.xib
index af7e8d3b..24a58d7c 100644
--- a/Demo/Demo/TacoDialogView.xib
+++ b/Demo/Demo/TacoDialogView.xib
@@ -1,12 +1,11 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14113" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES">
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES">
     <device id="retina4_7" orientation="portrait">
         <adaptation id="fullscreen"/>
     </device>
     <dependencies>
         <deployment identifier="iOS"/>
-        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14088"/>
-        <capability name="Constraints to layout margins" minToolsVersion="6.0"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14460.20"/>
         <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
     </dependencies>
     <objects>
@@ -17,22 +16,22 @@
             <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
             <subviews>
                 <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="dp3-Ae-zep" userLabel="Background view" customClass="CornerRoundingView" customModule="SwiftMessages">
-                    <rect key="frame" x="30" y="10" width="540" height="289"/>
+                    <rect key="frame" x="30" y="10" width="200" height="289"/>
                     <subviews>
                         <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" distribution="equalSpacing" spacing="10" translatesAutoresizingMaskIntoConstraints="NO" id="RJH-Fp-YDa" userLabel="Content view">
-                            <rect key="frame" x="30" y="30" width="480" height="229"/>
+                            <rect key="frame" x="30" y="30" width="140" height="229"/>
                             <subviews>
                                 <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" alignment="center" translatesAutoresizingMaskIntoConstraints="NO" id="Irk-mj-bK8">
-                                    <rect key="frame" x="0.0" y="0.0" width="480" height="60"/>
+                                    <rect key="frame" x="0.0" y="0.0" width="140" height="60"/>
                                     <subviews>
                                         <stackView opaque="NO" contentMode="scaleToFill" distribution="fillProportionally" alignment="center" spacing="15" translatesAutoresizingMaskIntoConstraints="NO" id="aav-a1-ogq">
-                                            <rect key="frame" x="0.0" y="0.0" width="480" height="60"/>
+                                            <rect key="frame" x="0.0" y="0.0" width="140" height="60"/>
                                             <subviews>
                                                 <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="xLT-bX-GJE">
-                                                    <rect key="frame" x="0.0" y="0.0" width="480" height="60"/>
+                                                    <rect key="frame" x="0.0" y="0.0" width="140" height="60"/>
                                                     <subviews>
                                                         <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="252" verticalHuggingPriority="251" horizontalCompressionResistancePriority="748" text="🌮" textAlignment="natural" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" minimumScaleFactor="0.5" translatesAutoresizingMaskIntoConstraints="NO" id="pFx-Py-lZQ" userLabel="Icon label">
-                                                            <rect key="frame" x="0.0" y="0.0" width="50" height="60"/>
+                                                            <rect key="frame" x="0.0" y="0.0" width="30.5" height="60"/>
                                                             <accessibility key="accessibilityConfiguration">
                                                                 <bool key="isElement" value="NO"/>
                                                             </accessibility>
@@ -44,7 +43,7 @@
                                                             <nil key="highlightedColor"/>
                                                         </label>
                                                         <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" horizontalCompressionResistancePriority="1000" text="Just one, please." textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="YAk-Zs-x2f">
-                                                            <rect key="frame" x="65" y="0.0" width="415" height="60"/>
+                                                            <rect key="frame" x="45.5" y="0.0" width="94.5" height="60"/>
                                                             <accessibility key="accessibilityConfiguration">
                                                                 <bool key="isElement" value="NO"/>
                                                             </accessibility>
@@ -70,7 +69,7 @@
                                     </subviews>
                                 </stackView>
                                 <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" verticalCompressionResistancePriority="748" text="How many tocos would you like?" textAlignment="center" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="gMT-Vh-S3z">
-                                    <rect key="frame" x="0.0" y="75.5" width="480" height="23.5"/>
+                                    <rect key="frame" x="0.0" y="70" width="140" height="46"/>
                                     <color key="backgroundColor" red="0.0" green="0.0" blue="0.0" alpha="0.0" colorSpace="custom" customColorSpace="sRGB"/>
                                     <accessibility key="accessibilityConfiguration">
                                         <bool key="isElement" value="NO"/>
@@ -80,13 +79,13 @@
                                     <nil key="highlightedColor"/>
                                 </label>
                                 <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Adjust the taco slider and place your order." textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="U9w-CI-YK7">
-                                    <rect key="frame" x="0.0" y="115" width="480" height="17"/>
+                                    <rect key="frame" x="0.0" y="126" width="140" height="17"/>
                                     <fontDescription key="fontDescription" name="Futura-CondensedMedium" family="Futura" pointSize="14"/>
                                     <color key="textColor" red="0.60392156862745094" green="0.44313725490196076" blue="0.10588235294117647" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                     <nil key="highlightedColor"/>
                                 </label>
                                 <slider opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" value="1" minValue="1" maxValue="5" translatesAutoresizingMaskIntoConstraints="NO" id="MKs-Kv-aPL">
-                                    <rect key="frame" x="-2" y="147.5" width="484" height="31"/>
+                                    <rect key="frame" x="-2" y="153" width="144" height="31"/>
                                     <color key="minimumTrackTintColor" red="0.94509803921568625" green="0.57647058823529407" blue="0.078431372549019607" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                     <connections>
                                         <action selector="tacoSliderFinished:" destination="JI3-gM-XBO" eventType="touchUpInside" id="ekV-4L-MLR"/>
@@ -95,10 +94,10 @@
                                     </connections>
                                 </slider>
                                 <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" alignment="bottom" translatesAutoresizingMaskIntoConstraints="NO" id="x8I-RG-nBX">
-                                    <rect key="frame" x="0.0" y="193" width="480" height="36"/>
+                                    <rect key="frame" x="0.0" y="193" width="140" height="36"/>
                                     <subviews>
                                         <stackView opaque="NO" contentMode="scaleToFill" spacing="15" translatesAutoresizingMaskIntoConstraints="NO" id="8Qt-TE-nPO">
-                                            <rect key="frame" x="323" y="0.0" width="157" height="36"/>
+                                            <rect key="frame" x="0.0" y="0.0" width="140" height="36"/>
                                             <subviews>
                                                 <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="yFi-Ik-klX">
                                                     <rect key="frame" x="0.0" y="0.0" width="58" height="36"/>
@@ -110,8 +109,8 @@
                                                         <action selector="cancel" destination="JI3-gM-XBO" eventType="touchUpInside" id="0BO-De-YH2"/>
                                                     </connections>
                                                 </button>
-                                                <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="rVu-Ei-t6A">
-                                                    <rect key="frame" x="73" y="0.0" width="84" height="36"/>
+                                                <button opaque="NO" contentMode="scaleToFill" horizontalCompressionResistancePriority="749" contentHorizontalAlignment="center" contentVerticalAlignment="center" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="rVu-Ei-t6A">
+                                                    <rect key="frame" x="73" y="0.0" width="67" height="36"/>
                                                     <color key="backgroundColor" red="0.94117647058823528" green="0.57647058823529407" blue="0.074509803921568626" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
                                                     <fontDescription key="fontDescription" name="Futura-Medium" family="Futura" pointSize="15"/>
                                                     <inset key="contentEdgeInsets" minX="8" minY="8" maxX="8" maxY="8"/>
@@ -138,6 +137,7 @@
                     <constraints>
                         <constraint firstAttribute="bottom" secondItem="RJH-Fp-YDa" secondAttribute="bottom" constant="30" id="3t4-62-KuN"/>
                         <constraint firstItem="RJH-Fp-YDa" firstAttribute="top" secondItem="dp3-Ae-zep" secondAttribute="top" constant="30" id="6rK-Yv-gKZ"/>
+                        <constraint firstAttribute="width" constant="200" id="TmJ-et-1je"/>
                         <constraint firstAttribute="trailing" secondItem="RJH-Fp-YDa" secondAttribute="trailing" constant="30" id="dJi-po-g6O"/>
                         <constraint firstItem="RJH-Fp-YDa" firstAttribute="leading" secondItem="dp3-Ae-zep" secondAttribute="leading" constant="30" id="zmH-aG-8Ij"/>
                     </constraints>
@@ -150,8 +150,7 @@
             </subviews>
             <color key="backgroundColor" red="0.0" green="0.0" blue="0.0" alpha="0.0" colorSpace="custom" customColorSpace="sRGB"/>
             <constraints>
-                <constraint firstAttribute="trailingMargin" secondItem="dp3-Ae-zep" secondAttribute="trailing" constant="10" id="gGP-zK-6VU"/>
-                <constraint firstItem="dp3-Ae-zep" firstAttribute="leading" secondItem="JI3-gM-XBO" secondAttribute="leadingMargin" constant="10" id="gyP-aD-uO3"/>
+                <constraint firstItem="dp3-Ae-zep" firstAttribute="leading" secondItem="JI3-gM-XBO" secondAttribute="leading" constant="30" id="aZp-9V-iCR"/>
                 <constraint firstAttribute="bottomMargin" secondItem="dp3-Ae-zep" secondAttribute="bottom" constant="10" id="le8-gK-lcY"/>
                 <constraint firstItem="dp3-Ae-zep" firstAttribute="top" secondItem="JI3-gM-XBO" secondAttribute="topMargin" constant="10" id="s15-z9-aHc"/>
             </constraints>
diff --git a/Demo/Demo/TestView.swift b/Demo/Demo/TestView.swift
new file mode 100644
index 00000000..0ca7c3ef
--- /dev/null
+++ b/Demo/Demo/TestView.swift
@@ -0,0 +1,14 @@
+//
+//  TestView.swift
+//  Demo
+//
+//  Created by Hanguang on 2019/3/13.
+//  Copyright © 2019 SwiftKick Mobile. All rights reserved.
+//
+
+import UIKit
+import SwiftMessages
+
+class TestView : MessageView {
+    
+}
diff --git a/Demo/Demo/TestViewController.swift b/Demo/Demo/TestViewController.swift
new file mode 100644
index 00000000..7cdad96c
--- /dev/null
+++ b/Demo/Demo/TestViewController.swift
@@ -0,0 +1,31 @@
+//
+//  TestViewController.swift
+//  Demo
+//
+//  Created by Hanguang on 2018/11/6.
+//  Copyright © 2018 SwiftKick Mobile. All rights reserved.
+//
+
+import UIKit
+
+class TestViewController: UIViewController {
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+
+        view.backgroundColor = .green
+        // Do any additional setup after loading the view.
+    }
+    
+
+    /*
+    // MARK: - Navigation
+
+    // In a storyboard-based application, you will often want to do a little preparation before navigation
+    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
+        // Get the new view controller using segue.destination.
+        // Pass the selected object to the new view controller.
+    }
+    */
+
+}
diff --git a/Demo/Demo/ViewController.swift b/Demo/Demo/ViewController.swift
index 045dfa30..2042940d 100644
--- a/Demo/Demo/ViewController.swift
+++ b/Demo/Demo/ViewController.swift
@@ -11,6 +11,22 @@ import SwiftMessages
 
 class ViewController: UITableViewController {
 
+    @IBAction func showPopover(_ sender: UIBarButtonItem, event: UIEvent) {
+        let view: AView = try! SwiftMessages.viewFromNib()
+        view.configureDropShadow()
+        
+        var config = SwiftMessages.defaultConfig
+        config.presentationContext = .window(windowLevel: UIWindow.Level.statusBar)
+        config.duration = .forever
+        let animator = CustomAnimation()
+        animator.popoverView = event.allTouches?.first?.view
+//        animator.placement = .center
+        config.presentationStyle = .custom(animator: animator)
+        config.interactiveHide = false
+        config.dimMode = .gray(interactive: true)
+        SwiftMessages.show(config: config, view: view)
+    }
+    
     var items: [Item] = [
         .titleBody(title: "MESSAGE VIEW", body: "SwiftMessages provides a standard message view along with a number of layouts, themes and presentation options.", function: ViewController.demoBasics),
         .titleBody(title: "ANY VIEW", body: "Any view, no matter how cute, can be displayed as a message.", function: ViewController.demoAnyView),
@@ -21,6 +37,10 @@ class ViewController: UITableViewController {
         //.counted,
     ]
 
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        navigationController?.setToolbarHidden(false, animated: true)
+    }
     /*
      MARK: - UITableViewDataSource
      */
@@ -136,14 +156,22 @@ class ViewController: UITableViewController {
     }
 
     static func demoCustomNib() {
-        let view: TacoDialogView = try! SwiftMessages.viewFromNib()
+//        let view: TacoDialogView = try! SwiftMessages.viewFromNib()
+//        view.configureDropShadow()
+//        view.getTacosAction = { _ in SwiftMessages.hide() }
+//        view.cancelAction = { SwiftMessages.hide() }
+        
+        let view: AView = try! SwiftMessages.viewFromNib()
+        view.position = CGPoint(x: 20, y: 100)
         view.configureDropShadow()
-        view.getTacosAction = { _ in SwiftMessages.hide() }
-        view.cancelAction = { SwiftMessages.hide() }
+        
         var config = SwiftMessages.defaultConfig
         config.presentationContext = .window(windowLevel: UIWindow.Level.statusBar)
         config.duration = .forever
-        config.presentationStyle = .bottom
+        let animator = CustomAnimation()
+//        animator.placement = .center
+        config.presentationStyle = .custom(animator: animator)
+        config.interactiveHide = false
         config.dimMode = .gray(interactive: true)
         SwiftMessages.show(config: config, view: view)
     }
diff --git a/Demo/Source/Stevia+Alignment.swift b/Demo/Source/Stevia+Alignment.swift
new file mode 100644
index 00000000..b1206a2f
--- /dev/null
+++ b/Demo/Source/Stevia+Alignment.swift
@@ -0,0 +1,366 @@
+//
+//  Stevia+Alignment.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+/** Aligns an array of views Horizontally (on the X Axis)
+ 
+ Example Usage:
+ ```
+ align(horizontally: label,button,arrow)
+ ```
+ 
+ Ca also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(horizontally: |-image1-image2-image3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(horizontally views: UIView...) -> [UIView] {
+    return align(horizontally: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(horizontally:)")
+@discardableResult
+public func alignHorizontally(_ views: UIView...) -> [UIView] {
+    return align(horizontally: views)
+}
+
+/** Aligns an array of views Horizontally (on the X Axis)
+ 
+ Example Usage:
+ ```
+ align(horizontally: label,button,arrow)
+ ```
+ 
+ Ca also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(horizontally: |-image1-image2-image3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(horizontally views: [UIView]) -> [UIView] {
+    align(.horizontal, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(horizontally:)")
+@discardableResult
+public func alignHorizontally(_ views: [UIView]) -> [UIView] {
+    align(.horizontal, views: views)
+    return views
+}
+
+/** Aligns an array of views Vertically (on the Y Axis)
+ 
+ Example Usage:
+ ```
+ align(vertically: label,field,button)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+public func align(vertically views: UIView...) {
+    align(vertically: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(vertically:)")
+public func alignVertically(_ views: UIView...) {
+    align(vertically: views)
+}
+
+/** Aligns an array of views Vertically (on the Y Axis)
+ 
+ Example Usage:
+ ```
+ align(vertically: label,field,button)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+public func align(vertically views: [UIView]) {
+    align(.vertical, views: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(vertically:)")
+public func alignVertically(_ views: [UIView]) {
+    align(.vertical, views: views)
+}
+
+/** Aligns the center of two views
+ 
+ Example Usage:
+ ```
+ alignCenter(button, with:image)
+ ```
+ */
+public func alignCenter(_ v1: UIView, with v2: UIView) {
+    alignHorizontally(v1, with: v2)
+    alignVertically(v1, with: v2)
+}
+
+/** Aligns two views Horizontall (on the X Axis)
+ 
+ Example Usage:
+ ```
+ alignHorizontally(label, with:field)
+ ```
+ 
+ */
+public func alignHorizontally(_ v1: UIView, with v2: UIView, offset: CGFloat = 0) {
+    align(.horizontal, v1: v1, with: v2, offset: offset)
+}
+
+/** Aligns two views Vertically (on the Y Axis)
+ 
+ Example Usage:
+ ```
+ alignVertically(label, with:field)
+ ```
+ 
+ */
+public func alignVertically(_ v1: UIView, with v2: UIView, offset: CGFloat = 0) {
+    align(.vertical, v1: v1, with: v2, offset: offset)
+}
+
+private func align(_ axis: NSLayoutConstraint.Axis, views: [UIView]) {
+    for (i, v) in views.enumerated() where views.count > i+1 {
+        let v2 = views[i+1]
+        if axis == .horizontal {
+            alignHorizontally(v, with: v2)
+        } else {
+            alignVertically(v, with: v2)
+        }
+    }
+}
+
+private func align(_ axis: NSLayoutConstraint.Axis, v1: UIView, with v2: UIView, offset: CGFloat) {
+    if let spv = v1.superview {
+        let center: NSLayoutConstraint.Attribute = axis == .horizontal ? .centerY : .centerX
+        let c = constraint(item: v1, attribute: center, toItem: v2, constant: offset)
+        spv.addConstraint(c)
+    }
+}
+
+// MARK: Align sides
+
+/** Aligns tops of an array of views
+ 
+ Example Usage:
+ ```
+ align(tops: label,button,arrow)
+ ```
+ 
+ Ca also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(tops: |-image1-image2-image3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(tops views: UIView...) -> [UIView] {
+    return align(tops: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(tops:)")
+@discardableResult
+public func alignTops(_ views: UIView...) -> [UIView] {
+    return align(tops: views)
+}
+
+/** Aligns tops of an array of views
+ 
+ Example Usage:
+ ```
+ align(tops: label,button,arrow)
+ ```
+ 
+ Ca also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(tops: |-image1-image2-image3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(tops views: [UIView]) -> [UIView] {
+    align(.top, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(tops:)")
+@discardableResult
+public func alignTops(_ views: [UIView]) -> [UIView] {
+    align(.top, views: views)
+    return views
+}
+
+/** Aligns bottoms of an array of views
+ 
+ Example Usage:
+ ```
+ align(bottoms: label,button,arrow)
+ ```
+ 
+ Ca also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(bottoms: |-image1-image2-image3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(bottoms views: UIView...) -> [UIView] {
+    return align(bottoms: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(bottoms:)")
+@discardableResult
+public func alignBottoms(_ views: UIView...) -> [UIView] {
+    return align(bottoms: views)
+}
+
+/** Aligns bottoms of an array of views
+ 
+ Example Usage:
+ ```
+ align(bottoms: label,button,arrow)
+ ```
+ 
+ Ca also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(bottoms: |-image1-image2-image3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(bottoms views: [UIView]) -> [UIView] {
+    align(.bottom, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(bottoms:)")
+@discardableResult
+public func alignBottoms(_ views: [UIView]) -> [UIView] {
+    align(.bottom, views: views)
+    return views
+}
+
+/** Aligns left sides of an array of views
+ 
+ Example Usage:
+ ```
+ align(lefts: label,field,button)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(lefts views: UIView...) -> [UIView] {
+    return align(lefts: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(lefts:)")
+@discardableResult
+public func alignLefts(_ views: UIView...) -> [UIView] {
+    return align(lefts: views)
+}
+
+/** Aligns left sides of an array of views
+ 
+ Example Usage:
+ ```
+ align(lefts: label,field,button)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(lefts views: [UIView]) -> [UIView] {
+    align(.left, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(lefts:)")
+@discardableResult
+public func alignLefts(_ views: [UIView]) -> [UIView] {
+    align(.left, views: views)
+    return views
+}
+
+/** Aligns right sides of an array of views
+ 
+ Example Usage:
+ ```
+ align(rights: label,field,button)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(rights views: UIView...) -> [UIView] {
+    return align(rights: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(rights:)")
+@discardableResult
+public func alignRights(_ views: UIView...) -> [UIView] {
+    return align(rights: views)
+}
+
+/** Aligns right sides of an array of views
+ 
+ Example Usage:
+ ```
+ align(rights: label,field,button)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(rights views: [UIView]) -> [UIView] {
+    align(.right, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed: "align(rights:)")
+@discardableResult
+public func alignRights(_ views: [UIView]) -> [UIView] {
+    align(.right, views: views)
+    return views
+}
+
+@discardableResult
+public func align(_ attribute: NSLayoutConstraint.Attribute, views: [UIView]) -> [UIView] {
+    for (i, v) in views.enumerated() where views.count > i+1 {
+        let v2 = views[i+1]
+        if let spv = v.superview {
+            let c = constraint(item: v, attribute: attribute, toItem: v2)
+            spv.addConstraint(c)
+        }
+    }
+    return views
+}
diff --git a/Demo/Source/Stevia+Baselines.swift b/Demo/Source/Stevia+Baselines.swift
new file mode 100644
index 00000000..73909a90
--- /dev/null
+++ b/Demo/Source/Stevia+Baselines.swift
@@ -0,0 +1,77 @@
+//
+//  Stevia+Baselines.swift
+//  Stevia
+//
+//  Created by Sacha on 09/09/2018.
+//  Copyright © 2018 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+/** Aligns an array of views by their lastBaselines (on the Y Axis)
+ 
+ Example Usage:
+ ```
+ align(lastBaselines: label1, label2, label3)
+ ```
+ 
+ Can also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(lastBaselines: |-label1-label2-label3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(lastBaselines views: UIView...) -> [UIView] {
+    return align(lastBaselines: views)
+}
+
+@discardableResult
+public func align(lastBaselines views: [UIView]) -> [UIView] {
+    for (i, v) in views.enumerated() where views.count > i+1 {
+        let v2 = views[i+1]
+        if #available(iOS 9.0, *) {
+            v.lastBaselineAnchor.constraint(equalTo: v2.lastBaselineAnchor).isActive = true
+        } else if let spv = v.superview {
+            let c = constraint(item: v, attribute: .lastBaseline, toItem: v2)
+            spv.addConstraint(c)
+        }
+    }
+    return views
+}
+
+/** Aligns an array of views by their firstBaselines (on the Y Axis)
+ 
+ Example Usage:
+ ```
+ align(firstBaselines: label1, label2, label3)
+ ```
+ 
+ Can also be used directly on horizontal layouts since they return the array of views :
+ ```
+ align(firstBaselines: |-label1-label2-label3-|)
+ ```
+ 
+ - Returns: The array of views, enabling chaining,
+ 
+ */
+@discardableResult
+public func align(firstBaselines views: UIView...) -> [UIView] {
+    return align(firstBaselines: views)
+}
+
+@discardableResult
+public func align(firstBaselines views: [UIView]) -> [UIView] {
+    for (i, v) in views.enumerated() where views.count > i+1 {
+        let v2 = views[i+1]
+        if #available(iOS 9.0, *) {
+            v.firstBaselineAnchor.constraint(equalTo: v2.firstBaselineAnchor).isActive = true
+        } else if let spv = v.superview {
+            let c = constraint(item: v, attribute: .firstBaseline, toItem: v2)
+            spv.addConstraint(c)
+        }
+    }
+    return views
+}
diff --git a/Demo/Source/Stevia+Center.swift b/Demo/Source/Stevia+Center.swift
new file mode 100644
index 00000000..dd4770f5
--- /dev/null
+++ b/Demo/Source/Stevia+Center.swift
@@ -0,0 +1,102 @@
+//
+//  Stevia+Center.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /**
+     Centers the view in its container.
+     
+     ```
+     button.centerInContainer()
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func centerInContainer() -> UIView {
+        if let spv = superview {
+            alignCenter(self, with: spv)
+        }
+        return self
+    }
+    
+    /**
+     Centers the view horizontally (X axis) in its container.
+     
+     ```
+     button.centerHorizontally()
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func centerHorizontally() -> UIView {
+        if let spv = superview {
+            align(vertically: self, spv)
+        }
+        return self
+    }
+    
+    /**
+     Centers the view vertically (Y axis) in its container.
+     
+     ```
+     button.centerVertically()
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func centerVertically() -> UIView {
+        if let spv = superview {
+            align(horizontally: self, spv)
+        }
+        return self
+    }
+    
+    /**
+     Centers the view horizontally (X axis) in its container, with an offset
+     
+     ```
+     button.centerHorizontally(40)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func centerHorizontally(_ offset: CGFloat) -> UIView {
+        if let spv = superview {
+            alignVertically(self, with: spv, offset: offset)
+        }
+        return self
+    }
+    
+    /**
+     Centers the view vertically (Y axis) in its container, with an offset
+     
+     ```
+     button.centerVertically(40)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func centerVertically(_ offset: CGFloat) -> UIView {
+        if let spv = superview {
+            alignHorizontally(self, with: spv, offset: offset)
+        }
+        return self
+    }
+}
diff --git a/Demo/Source/Stevia+Constraints.swift b/Demo/Source/Stevia+Constraints.swift
new file mode 100644
index 00000000..71d946b5
--- /dev/null
+++ b/Demo/Source/Stevia+Constraints.swift
@@ -0,0 +1,150 @@
+//
+//  Stevia+Constraints.swift
+//  LoginNadir
+//
+//  Created by Sacha Durand Saint Omer on 01/10/15.
+//  Copyright © 2015 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+// MARK: - Shortcut
+
+public extension UIView {
+    
+    /**
+     Helper for creating and adding NSLayoutConstraint but with default values provided.
+     
+     For instance
+     
+        addConstraint(item: view1, attribute: .CenterX, toItem: view2)
+     
+     is equivalent to
+     
+         addConstraint(
+            NSLayoutConstraint(item: view1,
+                attribute: .CenterX,
+                 relatedBy: .Equal,
+                 toItem: view2,
+                 attribute: .CenterX,
+                 multiplier: 1,
+                 constant: 0
+            )
+         )
+     
+     - Returns: The NSLayoutConstraint created.
+     */
+    @discardableResult
+    public func addConstraint(item view1: AnyObject,
+                              attribute attr1: NSLayoutConstraint.Attribute,
+                              relatedBy: NSLayoutConstraint.Relation = .equal,
+                              toItem view2: AnyObject? = nil,
+                              attribute attr2: NSLayoutConstraint.Attribute? = nil,
+                              multiplier: CGFloat = 1,
+                              constant: CGFloat = 0) -> NSLayoutConstraint {
+        let c = constraint(
+            item: view1, attribute: attr1,
+            relatedBy: relatedBy,
+            toItem: view2, attribute: attr2,
+            multiplier: multiplier, constant: constant)
+        addConstraint(c)
+        return c
+    }
+}
+
+/**
+    Helper for creating a NSLayoutConstraint but with default values provided.
+ 
+ For instance 
+ 
+        constraint(item: view1, attribute: .CenterX, toItem: view2)
+ 
+  is equivalent to
+ 
+        NSLayoutConstraint(item: view1, attribute: .CenterX,
+        relatedBy: .Equal,
+        toItem: view2, attribute: .CenterX,
+        multiplier: 1, constant: 0)
+ 
+    - Returns: The NSLayoutConstraint created.
+ */
+public func constraint(item view1: AnyObject,
+                       attribute attr1: NSLayoutConstraint.Attribute,
+                       relatedBy: NSLayoutConstraint.Relation = .equal,
+                       toItem view2: AnyObject? = nil,
+                       attribute attr2: NSLayoutConstraint.Attribute? = nil, // Not an attribute??
+                       multiplier: CGFloat = 1,
+                       constant: CGFloat = 0) -> NSLayoutConstraint {
+        let c =  NSLayoutConstraint(item: view1, attribute: attr1,
+                                  relatedBy: relatedBy,
+                                  toItem: view2, attribute: ((attr2 == nil) ? attr1 : attr2! ),
+                                  multiplier: multiplier, constant: constant)
+    c.priority = UILayoutPriority(rawValue: UILayoutPriority.defaultHigh.rawValue + 1)
+    return c
+}
+
+public extension UIView {
+
+/**
+     Get User added constraints. For making complex changes on layout, we need to remove user added constraints.
+     
+     If we remove all constraints, it may return broken layout.
+     
+     Use this method as:
+     
+        removeConstraints(userAddedConstraints)
+     
+*/
+    public var userAddedConstraints: [NSLayoutConstraint] {
+        return constraints.filter { c in
+            guard let cId = c.identifier else { return true }
+            return !cId.contains("UIView-Encapsulated-Layout") && !cId.contains("Margin-guide-constraint")
+        }
+    }
+}
+
+// MARK: - Other
+
+public extension UIView {
+
+    /**
+     Makes a view follow another view's frame.
+     For instance if we want a button to be on top of an image :
+     
+     ```
+     button.followEdges(image)
+     ```
+     */
+    public func followEdges(_ otherView: UIView) {
+        if let spv = superview {
+            let cs = [
+                constraint(item: self, attribute: .top, toItem: otherView),
+                constraint(item: self, attribute: .right, toItem: otherView),
+                constraint(item: self, attribute: .bottom, toItem: otherView),
+                constraint(item: self, attribute: .left, toItem: otherView)
+            ]
+            spv.addConstraints(cs)
+        }
+    }
+    
+    /**
+     Enforce a view to keep height and width equal at all times, essentially
+     forcing it to be a square.
+     
+     ```
+     image.heightEqualsWidth()
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func heightEqualsWidth() -> UIView {
+        if let spv = superview {
+            let c = constraint(item: self, attribute: .height, toItem: self, attribute: .width)
+            spv.addConstraint(c)
+        }
+        return self
+    }
+    
+}
diff --git a/Demo/Source/Stevia+Content.swift b/Demo/Source/Stevia+Content.swift
new file mode 100644
index 00000000..f84cc64f
--- /dev/null
+++ b/Demo/Source/Stevia+Content.swift
@@ -0,0 +1,102 @@
+//
+//  Stevia+Content.swift
+//  LoginStevia
+//
+//  Created by Sacha Durand Saint Omer on 01/10/15.
+//  Copyright © 2015 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIButton {
+    
+    /**
+     Sets the title of the button for normal State
+     
+     Essentially a shortcut for `setTitle("MyText", forState: .Normal)`
+     
+     - Returns: Itself for chaining purposes
+    */
+    @discardableResult
+    public func text(_ t: String) -> Self {
+        setTitle(t, for: .normal)
+        return self
+    }
+    
+    /**
+     Sets the localized key for the button's title in normal State
+     
+     Essentially a shortcut for `setTitle(NSLocalizedString("MyText", comment: "")
+     , forState: .Normal)`
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func textKey(_ t: String) -> Self {
+        text(NSLocalizedString(t, comment: ""))
+        return self
+    }
+    
+    /**
+     Sets the image of the button in normal State
+     
+     Essentially a shortcut for `setImage(UIImage(named:"X"), forState: .Normal)`
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func image(_ s: String) -> Self {
+        setImage(UIImage(named: s), for: .normal)
+        return self
+    }
+}
+
+public extension UITextField {
+    /**
+     Sets the textfield placeholder but in a chainable fashion
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func placeholder(_ t: String) -> Self {
+        placeholder = t
+        return self
+    }
+}
+
+public extension UILabel {
+    /**
+     Sets the label text but in a chainable fashion
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func text(_ t: String) -> Self {
+        text = t
+        return self
+    }
+    
+    /**
+     Sets the label localization key but in a chainable fashion
+     Essentially a shortcut for `text = NSLocalizedString("X", comment: "")`
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func textKey(_ t: String) -> Self {
+        text(NSLocalizedString(t, comment: ""))
+        return self
+    }
+}
+
+extension UIImageView {
+    /**
+     Sets the image of the imageView but in a chainable fashion
+     
+     Essentially a shortcut for `image = UIImage(named: "X")`
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func image(_ t: String) -> Self {
+        image = UIImage(named: t)
+        return self
+    }
+}
diff --git a/Demo/Source/Stevia+DoubleDash.swift b/Demo/Source/Stevia+DoubleDash.swift
new file mode 100644
index 00000000..506b2155
--- /dev/null
+++ b/Demo/Source/Stevia+DoubleDash.swift
@@ -0,0 +1,98 @@
+//
+//  Stevia+DoubleDash.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 03/05/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+infix operator -- :AdditionPrecedence
+
+@discardableResult
+public func -- (left: UIView, right: CGFloat) -> PartialConstraint {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: SideConstraint, right: UIView) -> UIView {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: [UIView], right: SideConstraint) -> [UIView] {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: UIView, right: SideConstraint) -> UIView {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: PartialConstraint, right: UIView) -> [UIView] {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: UIView, right: UIView) -> [UIView] {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: [UIView], right: CGFloat) -> PartialConstraint {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: [UIView], right: UIView) -> [UIView] {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: UIView, right: String) -> Space {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: [UIView], right: String) -> Space {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: Space, right: UIView) -> [UIView] {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: UIView,
+                right: SteviaFlexibleMargin) -> PartialFlexibleConstraint {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: [UIView],
+                right: SteviaFlexibleMargin) -> PartialFlexibleConstraint {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: PartialFlexibleConstraint, right: UIView) -> [UIView] {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: SteviaLeftFlexibleMargin, right: UIView) -> UIView {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: UIView, right: SteviaRightFlexibleMargin) -> UIView {
+    return left-right
+}
+
+@discardableResult
+public func -- (left: [UIView], right: SteviaRightFlexibleMargin) -> [UIView] {
+    return left-right
+}
diff --git a/Demo/Source/Stevia+Equation.swift b/Demo/Source/Stevia+Equation.swift
new file mode 100644
index 00000000..fecace0d
--- /dev/null
+++ b/Demo/Source/Stevia+Equation.swift
@@ -0,0 +1,252 @@
+//
+//  Stevia+Equation.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 21/01/2017.
+//  Copyright © 2017 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public struct SteviaAttribute {
+    let view: UIView
+    let attribute: NSLayoutConstraint.Attribute
+    let constant: CGFloat?
+    let multiplier: CGFloat?
+    
+    init(view: UIView, attribute: NSLayoutConstraint.Attribute) {
+        self.view = view
+        self.attribute = attribute
+        self.constant = nil
+        self.multiplier = nil
+    }
+    
+    init(view: UIView, attribute: NSLayoutConstraint.Attribute, constant: CGFloat?, multiplier: CGFloat?) {
+        self.view = view
+        self.attribute = attribute
+        self.constant = constant
+        self.multiplier = multiplier
+    }
+}
+
+public extension UIView {
+    
+    public var Width: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .width)
+    }
+    
+    public var Height: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .height)
+    }
+    
+    public var Top: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .top)
+    }
+    
+    public var Bottom: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .bottom)
+    }
+    
+    public var Left: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .left)
+    }
+    
+    public var Right: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .right)
+    }
+    
+    public var Leading: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .leading)
+    }
+    
+    public var Trailing: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .trailing)
+    }
+    
+    public var CenterX: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .centerX)
+    }
+    
+    public var CenterY: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .centerY)
+    }
+    
+    public var FirstBaseline: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .firstBaseline)
+    }
+    
+    public var LastBaseline: SteviaAttribute {
+        return SteviaAttribute(view: self, attribute: .lastBaseline)
+    }
+}
+
+// MARK: - Equations of type v.P == v'.P' + X
+
+@discardableResult
+public func == (left: SteviaAttribute, right: SteviaAttribute) -> NSLayoutConstraint {
+    let constant = right.constant ?? left.constant ?? 0
+    let multiplier = right.multiplier ?? left.multiplier ?? 1
+
+    if left.view.superview == right.view.superview { // A and B are at the same level
+        // Old code
+        if let spv = left.view.superview {
+            return spv.addConstraint(item: left.view,
+                                     attribute: left.attribute,
+                                     toItem: right.view,
+                                     attribute: right.attribute,
+                                     multiplier: multiplier,
+                                     constant: constant)
+        }
+    } else if left.view.superview == right.view { // A is in B (first level)
+        return right.view.addConstraint(item: left.view,
+                                        attribute: left.attribute,
+                                        toItem: right.view,
+                                        attribute: right.attribute,
+                                        multiplier: multiplier,
+                                        constant: constant)
+    } else if right.view.superview == left.view { // B is in A (first level)
+        return left.view.addConstraint(item: right.view,
+                                       attribute: right.attribute,
+                                       toItem: left.view,
+                                       attribute: left.attribute,
+                                       multiplier: multiplier,
+                                       constant: constant)
+    } else if left.view.isDescendant(of: right.view) { // A is in B (LOW level)
+        return right.view.addConstraint(item: left.view,
+                                        attribute: left.attribute,
+                                        toItem: right.view,
+                                        attribute: right.attribute,
+                                        multiplier: multiplier,
+                                        constant: constant)
+    } else if right.view.isDescendant(of: left.view) { // B is in A (LOW level)
+        return left.view.addConstraint(item: left.view,
+                                       attribute: left.attribute,
+                                       toItem: right.view,
+                                       attribute: right.attribute,
+                                       multiplier: multiplier,
+                                       constant: constant)
+    } else if let commonParent = commonParent(with: left.view, and: right.view) { // Look for common ancestor
+        return commonParent.addConstraint(item: left.view,
+                                          attribute: left.attribute,
+                                          toItem: right.view,
+                                          attribute: right.attribute,
+                                          multiplier: multiplier,
+                                          constant: constant)
+    }
+    
+    return NSLayoutConstraint()
+}
+
+func commonParent(with viewA: UIView, and viewB: UIView) -> UIView? {
+    
+    // Both views should have a superview
+    guard viewA.superview != nil && viewB.superview != nil else {
+        return nil
+    }
+    
+    // Find the common parent
+    var spv = viewA.superview
+    while spv != nil {
+        if viewA.isDescendant(of: spv!) && viewB.isDescendant(of: spv!) {
+            return spv
+        } else {
+            spv = spv?.superview
+        }
+    }
+    return nil
+}
+
+@discardableResult
+public func >= (left: SteviaAttribute, right: SteviaAttribute) -> NSLayoutConstraint {
+    return applyRelation(left: left, right: right, relateBy: .greaterThanOrEqual)
+}
+
+@discardableResult
+public func <= (left: SteviaAttribute, right: SteviaAttribute) -> NSLayoutConstraint {
+    return applyRelation(left: left, right: right, relateBy: .lessThanOrEqual)
+}
+
+private func applyRelation(left: SteviaAttribute, right: SteviaAttribute, relateBy: NSLayoutConstraint.Relation) -> NSLayoutConstraint {
+    let constant = right.constant ?? 0
+    let multiplier = right.multiplier ?? 1
+    if let spv = left.view.superview {
+        return spv.addConstraint(item: left.view,
+                                 attribute: left.attribute,
+                                 relatedBy: relateBy,
+                                 toItem: right.view,
+                                 attribute: right.attribute,
+                                 multiplier: multiplier,
+                                 constant: constant)
+    }
+    return NSLayoutConstraint()
+}
+
+@discardableResult
+public func + (left: SteviaAttribute, right: CGFloat) -> SteviaAttribute {
+    return SteviaAttribute(view: left.view, attribute: left.attribute, constant: right, multiplier: left.multiplier)
+}
+
+@discardableResult
+public func - (left: SteviaAttribute, right: CGFloat) -> SteviaAttribute {
+    return SteviaAttribute(view: left.view, attribute: left.attribute, constant: -right, multiplier: left.multiplier)
+}
+
+@discardableResult
+public func * (left: SteviaAttribute, right: CGFloat) -> SteviaAttribute {
+    return SteviaAttribute(view: left.view, attribute: left.attribute, constant: left.constant, multiplier: right)
+}
+
+@discardableResult
+public func / (left: SteviaAttribute, right: CGFloat) -> SteviaAttribute {
+    return left * (1/right)
+}
+
+@discardableResult
+public func % (left: CGFloat, right: SteviaAttribute) -> SteviaAttribute {
+    return right * (left/100)
+}
+
+// MARK: - Equations of type v.P == X
+
+@discardableResult
+public func == (left: SteviaAttribute, right: CGFloat) -> NSLayoutConstraint {
+    if let spv = left.view.superview {
+        var toItem: UIView? = spv
+        var constant: CGFloat = right
+        if left.attribute == .width || left.attribute == .height {
+            toItem = nil
+        }
+        if left.attribute == .bottom || left.attribute == .right {
+            constant = -constant
+        }
+        return spv.addConstraint(item: left.view,
+                                 attribute: left.attribute,
+                                 toItem: toItem,
+                                 constant: constant)
+    }
+    return NSLayoutConstraint()
+}
+
+@discardableResult
+public func >= (left: SteviaAttribute, right: CGFloat) -> NSLayoutConstraint {
+    if let spv = left.view.superview {
+        return spv.addConstraint(item: left.view,
+                                 attribute: left.attribute,
+                                 relatedBy: .greaterThanOrEqual,
+                                 toItem: spv,
+                                 constant: right)
+    }
+    return NSLayoutConstraint()
+}
+
+@discardableResult
+public func <= (left: SteviaAttribute, right: CGFloat) -> NSLayoutConstraint {
+    if let spv = left.view.superview {
+        return spv.addConstraint(item: left.view,
+                                 attribute: left.attribute,
+                                 relatedBy: .lessThanOrEqual,
+                                 toItem: spv,
+                                 constant: right)
+    }
+    return NSLayoutConstraint()
+}
diff --git a/Demo/Source/Stevia+Fill.swift b/Demo/Source/Stevia+Fill.swift
new file mode 100644
index 00000000..88602a37
--- /dev/null
+++ b/Demo/Source/Stevia+Fill.swift
@@ -0,0 +1,70 @@
+//
+//  Stevia+Fill.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /**
+     Adds the constraints needed for the view to fill its `superview`.
+     A padding can be used to apply equal spaces between the view and its superview
+    */
+    @discardableResult
+    public func fillContainer(_ padding: CGFloat = 0) -> UIView {
+        fillHorizontally(m: padding)
+        fillVertically(m: padding)
+        return self
+    }
+    
+    @available(*, deprecated: 2.2.1, message: "Use 'fillVertically' instead")
+    /**
+     Adds the constraints needed for the view to fill its `superview` Vertically.
+     A padding can be used to apply equal spaces between the view and its superview
+     */
+    public func fillV(m points: CGFloat = 0) -> UIView {
+        return fill(.vertical, points: points)
+    }
+    
+    /**
+     Adds the constraints needed for the view to fill its `superview` Vertically.
+     A padding can be used to apply equal spaces between the view and its superview
+     */
+    @discardableResult
+    public func fillVertically(m points: CGFloat = 0) -> UIView {
+        return fill(.vertical, points: points)
+    }
+    
+    @available(*, deprecated: 2.2.1, message: "Use 'fillHorizontally' instead")
+    /**
+     Adds the constraints needed for the view to fill its `superview` Horizontally.
+     A padding can be used to apply equal spaces between the view and its superview
+     */
+    public func fillH(m points: CGFloat = 0) -> UIView {
+        return fill(.horizontal, points: points)
+    }
+    
+    /**
+     Adds the constraints needed for the view to fill its `superview` Horizontally.
+     A padding can be used to apply equal spaces between the view and its superview
+     */
+    @discardableResult
+    public func fillHorizontally(m points: CGFloat = 0) -> UIView {
+        return fill(.horizontal, points: points)
+    }
+    
+    fileprivate func fill(_ axis: NSLayoutConstraint.Axis, points: CGFloat = 0) -> UIView {
+        let a: NSLayoutConstraint.Attribute = axis == .vertical ? .top : .left
+        let b: NSLayoutConstraint.Attribute = axis == .vertical ? .bottom : .right
+        if let spv = superview {
+            let c1 = constraint(item: self, attribute: a, toItem: spv, constant: points)
+            let c2 = constraint(item: self, attribute: b, toItem: spv, constant: -points)
+            spv.addConstraints([c1, c2])
+        }
+        return self
+    }
+}
diff --git a/Demo/Source/Stevia+FlexibleMargin.swift b/Demo/Source/Stevia+FlexibleMargin.swift
new file mode 100644
index 00000000..8604cd2f
--- /dev/null
+++ b/Demo/Source/Stevia+FlexibleMargin.swift
@@ -0,0 +1,126 @@
+//
+//  Stevia+FlexibleMargin.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/07/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+prefix operator >=
+@discardableResult
+public prefix func >= (p: CGFloat) -> SteviaFlexibleMargin {
+    return SteviaFlexibleMargin(points: p, relation: .greaterThanOrEqual)
+}
+
+prefix operator <=
+@discardableResult
+public prefix func <= (p: CGFloat) -> SteviaFlexibleMargin {
+    return SteviaFlexibleMargin(points: p, relation: .lessThanOrEqual)
+}
+
+public struct SteviaFlexibleMargin {
+    var points: CGFloat!
+    var relation: NSLayoutConstraint.Relation!
+}
+
+public struct PartialFlexibleConstraint {
+    var fm: SteviaFlexibleMargin!
+    var view1: UIView?
+    var views: [UIView]?
+}
+
+@discardableResult
+public func - (left: UIView,
+               right: SteviaFlexibleMargin) -> PartialFlexibleConstraint {
+    return PartialFlexibleConstraint(fm: right, view1: left, views: nil)
+}
+
+@discardableResult
+public func - (left: [UIView],
+               right: SteviaFlexibleMargin) -> PartialFlexibleConstraint {
+    return PartialFlexibleConstraint(fm: right, view1: nil, views: left)
+}
+
+@discardableResult
+public func - (left: PartialFlexibleConstraint, right: UIView) -> [UIView] {
+    if let views = left.views {
+        if let spv = right.superview {
+            let c = constraint(item: right, attribute: .left,
+                               relatedBy: left.fm.relation, toItem: views.last,
+                               attribute: .right,
+                               constant: left.fm.points)
+            spv.addConstraint(c)
+        }
+        return views + [right]
+    } else {
+        if let spv = right.superview {
+            let c = constraint(item: right, attribute: .left,
+                               relatedBy: left.fm.relation, toItem: left.view1!,
+                               attribute: .right,
+                               constant: left.fm.points)
+            spv.addConstraint(c)
+        }
+        return [left.view1!, right]
+    }
+}
+
+// Left Flexible margin
+
+public struct SteviaLeftFlexibleMargin {
+    let fm: SteviaFlexibleMargin
+}
+
+@discardableResult
+public prefix func |- (fm: SteviaFlexibleMargin) -> SteviaLeftFlexibleMargin {
+    return SteviaLeftFlexibleMargin(fm: fm)
+}
+
+@discardableResult
+public func - (left: SteviaLeftFlexibleMargin, right: UIView) -> UIView {
+    if let spv = right.superview {
+        let c = constraint(item: right, attribute: .left,
+                           relatedBy: left.fm.relation, toItem: spv,
+                           attribute: .left,
+                           constant: left.fm.points)
+        spv.addConstraint(c)
+    }
+    return right
+}
+
+// Right Flexible margin
+
+public struct SteviaRightFlexibleMargin {
+    let fm: SteviaFlexibleMargin
+}
+
+@discardableResult
+public postfix func -| (fm: SteviaFlexibleMargin) -> SteviaRightFlexibleMargin {
+    return SteviaRightFlexibleMargin(fm: fm)
+}
+
+@discardableResult
+public func - (left: UIView, right: SteviaRightFlexibleMargin) -> UIView {
+    if let spv = left.superview {
+        let c = constraint(item: spv, attribute: .right,
+                           relatedBy: right.fm.relation, toItem: left,
+                           attribute: .right,
+                           constant: right.fm.points)
+        spv.addConstraint(c)
+    }
+    return left
+}
+
+@discardableResult
+public func - (left: [UIView], right: SteviaRightFlexibleMargin) -> [UIView] {
+    if let spv = left.last!.superview {
+        let c = constraint(item: spv, attribute: .right,
+                           relatedBy: right.fm.relation,
+                           toItem: left.last!,
+                           attribute: .right,
+                           constant: right.fm.points)
+        spv.addConstraint(c)
+    }
+    return left
+}
diff --git a/Demo/Source/Stevia+GetConstraint.swift b/Demo/Source/Stevia+GetConstraint.swift
new file mode 100644
index 00000000..43971ee9
--- /dev/null
+++ b/Demo/Source/Stevia+GetConstraint.swift
@@ -0,0 +1,197 @@
+//
+//  Stevia+GetConstraint.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 12/03/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /** Gets the left constraint if found.
+    
+    Example Usage for changing left margin of a label :
+    ```
+    label.leftConstraint?.constant = 10
+     
+    // Animate if needed
+    UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+    ```
+    - Returns: The left NSLayoutConstraint if found.
+     */
+    public var leftConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .left)
+    }
+
+    /** Gets the right constraint if found.
+     
+    Example Usage for changing right margin of a label :
+     
+    ```
+    label.rightConstraint?.constant = 10
+     
+    // Animate if needed
+    UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+    ```
+    - Returns: The right NSLayoutConstraint if found.
+     */
+    public var rightConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .right)
+    }
+        
+    /** Gets the top constraint if found.
+     
+    Example Usage for changing top margin of a label :
+     
+    ```
+    label.topConstraint?.constant = 10
+     
+    // Animate if needed
+    UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+    ```
+    - Returns: The top NSLayoutConstraint if found.
+     */
+    public var topConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .top)
+    }
+    
+    /** Gets the bottom constraint if found.
+    
+    Example Usage for changing bottom margin of a label :
+     
+    ```
+    label.bottomConstraint?.constant = 10
+    
+    // Animate if needed
+    UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+    ```
+     - Returns: The bottom NSLayoutConstraint if found.
+     */
+    public var bottomConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .bottom)
+    }
+    
+    /** Gets the height constraint if found.
+     
+    Example Usage for changing height property of a label :
+     
+    ```
+    label.heightConstraint?.constant = 10
+     
+    // Animate if needed
+    UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+    ```
+    - Returns: The height NSLayoutConstraint if found.
+    */
+    public var heightConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .height)
+    }
+    
+    /** Gets the width constraint if found.
+     
+     Example Usage for changing width property of a label :
+     
+     ```
+     label.widthConstraint?.constant = 10
+     
+     // Animate if needed
+     UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+     ```
+     - Returns: The width NSLayoutConstraint if found.
+     */
+    public var widthConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .width)
+    }
+    
+    /** Gets the trailing constraint if found.
+     
+     Example Usage for changing width property of a label :
+     
+     ```
+     label.trailingConstraint?.constant = 10
+     
+     // Animate if needed
+     UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+     ```
+     - Returns: The trailing NSLayoutConstraint if found.
+     */
+    public var trailingConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .trailing)
+    }
+    
+    /** Gets the leading constraint if found.
+     
+     Example Usage for changing width property of a label :
+     
+     ```
+     label.leadingConstraint?.constant = 10
+     
+     // Animate if needed
+     UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+     ```
+     - Returns: The leading NSLayoutConstraint if found.
+     */
+    public var leadingConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .leading)
+    }
+    
+    /** Gets the centerX constraint if found.
+     
+     Example Usage for changing width property of a label :
+     
+     ```
+     label.centerXConstraint?.constant = 10
+     
+     // Animate if needed
+     UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+     ```
+     - Returns: The width NSLayoutConstraint if found.
+     */
+    public var centerXConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .centerX)
+    }
+    
+    /** Gets the centerY constraint if found.
+     
+     Example Usage for changing width property of a label :
+     
+     ```
+     label.centerYConstraint?.constant = 10
+     
+     // Animate if needed
+     UIView.animateWithDuration(0.3, animations:layoutIfNeeded)
+     ```
+     - Returns: The width NSLayoutConstraint if found.
+     */
+    public var centerYConstraint: NSLayoutConstraint? {
+        return constraintForView(self, attribute: .centerY)
+    }
+}
+
+func constraintForView(_ v: UIView, attribute: NSLayoutConstraint.Attribute) -> NSLayoutConstraint? {
+    
+    func lookForConstraint(in view: UIView?) -> NSLayoutConstraint? {
+        guard let constraints = view?.constraints else {
+            return nil
+        }
+        for c in constraints {
+            if let fi = c.firstItem as? NSObject, fi == v && c.firstAttribute == attribute {
+                return c
+            } else if let si = c.secondItem as? NSObject, si == v && c.secondAttribute == attribute {
+                return c
+            }
+        }
+        return nil
+    }
+    
+    // Width and height constraints added via widthAnchor/heightAnchors are
+    // added on the view itself.
+    if (attribute == .width || attribute == .height) {
+        return lookForConstraint(in: v.superview) ?? lookForConstraint(in: v)
+    }
+    
+    // Look for constraint on superview.
+    return lookForConstraint(in: v.superview)
+}
diff --git a/Demo/Source/Stevia+Hierarchy.swift b/Demo/Source/Stevia+Hierarchy.swift
new file mode 100644
index 00000000..60792823
--- /dev/null
+++ b/Demo/Source/Stevia+Hierarchy.swift
@@ -0,0 +1,165 @@
+//
+//  Stevia+Hierarchy.swift
+//  LoginStevia
+//
+//  Created by Sacha Durand Saint Omer on 01/10/15.
+//  Copyright © 2015 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /**
+     Defines the view hierachy for the view.
+     
+     Esentially, this is just a shortcut to `addSubview`
+     and 'translatesAutoresizingMaskIntoConstraints = false'
+     
+     
+     
+     ```
+     class MyView: UIView {
+     
+     let email = UITextField()
+     let password = UITextField()
+     let login = UIButton()
+     
+        convenience init() {
+        self.init(frame: CGRect.zero)
+     
+         sv(
+            email,
+            password,
+            login
+         )
+        ...
+     
+        }
+     }
+     
+     ```
+     
+     - Returns: Itself to enable nested layouts.
+     */
+    @discardableResult
+    public func sv(_ subViews: UIView...) -> UIView {
+        return sv(subViews)
+    }
+
+    /**
+     Defines the view hierachy for the view.
+     
+     Esentially, this is just a shortcut to `addSubview`
+     and 'translatesAutoresizingMaskIntoConstraints = false'
+     
+     
+     ```
+     class MyView: UIView {
+     
+     let email = UITextField()
+     let password = UITextField()
+     let login = UIButton()
+     
+         convenience init() {
+         self.init(frame: CGRect.zero)
+         
+         sv(
+            email,
+            password,
+            login
+         )
+     ...
+     
+     }
+     }
+     
+     ```
+     
+     - Returns: Itself to enable nested layouts.
+     */
+    @objc @discardableResult
+    public func sv(_ subViews: [UIView]) -> UIView {
+        for sv in subViews {
+            addSubview(sv)
+            sv.translatesAutoresizingMaskIntoConstraints = false
+        }
+        return self
+    }
+}
+
+public extension UITableViewCell {
+    
+    /**
+     Defines the view hierachy for the view.
+     
+     Esentially, this is just a shortcut to `contentView.addSubview`
+     and 'translatesAutoresizingMaskIntoConstraints = false'
+     
+     ```
+     class NotificationCell: UITableViewCell {
+    
+        var avatar = UIImageView()
+        var name = UILabel()
+        var followButton = UIButton()
+     
+         required init?(coder aDecoder: NSCoder) { super.init(coder: aDecoder) }
+         override init(style: UITableViewCellStyle, reuseIdentifier: String?) {
+         super.init(style: style, reuseIdentifier: reuseIdentifier) {
+     
+             sv(
+                avatar,
+                name,
+                followButton
+            )
+        ...
+     
+        }
+     }
+     ```
+     
+     - Returns: Itself to enable nested layouts.
+     */
+    @discardableResult
+    public override func sv(_ subViews: [UIView]) -> UIView {
+        return contentView.sv(subViews)
+    }
+}
+
+public extension UICollectionViewCell {
+    /**
+     Defines the view hierachy for the view.
+     
+     Esentially, this is just a shortcut to `contentView.addSubview`
+     and 'translatesAutoresizingMaskIntoConstraints = false'
+     
+     ```
+     class PhotoCollectionViewCell: UICollectionViewCell {
+     
+     var avatar = UIImageView()
+     var name = UILabel()
+     var followButton = UIButton()
+     
+     
+     required init?(coder aDecoder: NSCoder) { fatalError("init(coder:) has not been implemented") }
+     override init(frame: CGRect) {
+     super.init(frame: frame)
+     
+         sv(
+            avatar,
+            name,
+            followButton
+         )
+     ...
+     
+     }
+     }
+     ```
+     
+     - Returns: Itself to enable nested layouts.
+     */
+    @discardableResult
+    public override func sv(_ subViews: [UIView]) -> UIView {
+        return contentView.sv(subViews)
+    }
+}
diff --git a/Demo/Source/Stevia+LayoutAnchors.swift b/Demo/Source/Stevia+LayoutAnchors.swift
new file mode 100644
index 00000000..bc985947
--- /dev/null
+++ b/Demo/Source/Stevia+LayoutAnchors.swift
@@ -0,0 +1,151 @@
+//
+//  Stevia+LayoutAnchors.swift
+//  Stevia
+//
+//  Created by Sacha DSO on 09/10/2017.
+//  Copyright © 2017 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+@available(iOS 9.0, *)
+public struct SteviaLayoutYAxisAnchor {
+    let anchor: NSLayoutYAxisAnchor
+    let constant: CGFloat
+    
+    init(anchor: NSLayoutYAxisAnchor, constant: CGFloat = 0) {
+        self.anchor = anchor
+        self.constant = constant
+    }
+}
+
+@available(iOS 9.0, *)
+public struct SteviaLayoutXAxisAnchor {
+    let anchor: NSLayoutXAxisAnchor
+    let constant: CGFloat
+    
+    init(anchor: NSLayoutXAxisAnchor, constant: CGFloat = 0) {
+        self.anchor = anchor
+        self.constant = constant
+    }
+}
+
+@available(iOS 9.0, *)
+public extension UILayoutGuide {
+
+    public var Top: SteviaLayoutYAxisAnchor {
+        return SteviaLayoutYAxisAnchor(anchor: topAnchor)
+    }
+
+    public var Bottom: SteviaLayoutYAxisAnchor {
+        return SteviaLayoutYAxisAnchor(anchor: bottomAnchor)
+    }
+    
+    public var Left: SteviaLayoutXAxisAnchor {
+        return SteviaLayoutXAxisAnchor(anchor: leftAnchor)
+    }
+    
+    public var Right: SteviaLayoutXAxisAnchor {
+        return SteviaLayoutXAxisAnchor(anchor: rightAnchor)
+    }
+    
+    public var Leading: SteviaLayoutXAxisAnchor {
+        return SteviaLayoutXAxisAnchor(anchor: leadingAnchor)
+    }
+    
+    public var Trailing: SteviaLayoutXAxisAnchor {
+        return SteviaLayoutXAxisAnchor(anchor: trailingAnchor)
+    }
+
+    public var CenterX: SteviaLayoutXAxisAnchor {
+        return SteviaLayoutXAxisAnchor(anchor: centerXAnchor)
+    }
+    
+    public var CenterY: SteviaLayoutYAxisAnchor {
+        return SteviaLayoutYAxisAnchor(anchor: centerYAnchor)
+    }
+}
+
+@available(iOS 9.0, *)
+@discardableResult
+public func == (left: SteviaAttribute, right: SteviaLayoutYAxisAnchor) -> NSLayoutConstraint {
+    
+    var constraint = NSLayoutConstraint()
+    
+    if left.attribute == .top {
+        constraint = left.view.topAnchor.constraint(equalTo: right.anchor, constant: right.constant)
+    }
+    
+    if left.attribute == .bottom {
+        constraint = left.view.bottomAnchor.constraint(equalTo: right.anchor, constant: right.constant)
+    }
+    
+    constraint.isActive = true
+    return constraint
+}
+
+@available(iOS 9.0, *)
+@discardableResult
+public func == (left: SteviaAttribute, right: SteviaLayoutXAxisAnchor) -> NSLayoutConstraint {
+    
+    var constraint = NSLayoutConstraint()
+    
+    if left.attribute == .left {
+        constraint = left.view.leftAnchor.constraint(equalTo: right.anchor, constant: right.constant)
+    }
+    
+    if left.attribute == .right {
+        constraint = left.view.rightAnchor.constraint(equalTo: right.anchor, constant: right.constant)
+    }
+    
+    if left.attribute == .leading {
+        constraint = left.view.leadingAnchor.constraint(equalTo: right.anchor, constant: right.constant)
+    }
+    
+    if left.attribute == .trailing {
+        constraint = left.view.trailingAnchor.constraint(equalTo: right.anchor, constant: right.constant)
+    }
+    
+    constraint.isActive = true
+    return constraint
+}
+
+// SteviaLayoutYAxisAnchor
+
+@available(iOS 9.0, *)
+@discardableResult
+public func + (left: SteviaLayoutYAxisAnchor, right: CGFloat) -> SteviaLayoutYAxisAnchor {
+    return SteviaLayoutYAxisAnchor(anchor: left.anchor, constant: right)
+}
+
+@available(iOS 9.0, *)
+@discardableResult
+public func - (left: SteviaLayoutYAxisAnchor, right: CGFloat) -> SteviaLayoutYAxisAnchor {
+    return SteviaLayoutYAxisAnchor(anchor: left.anchor, constant: -right)
+}
+
+@available(iOS 9.0, *)
+@discardableResult
+public func + (left: SteviaLayoutXAxisAnchor, right: CGFloat) -> SteviaLayoutXAxisAnchor {
+    return SteviaLayoutXAxisAnchor(anchor: left.anchor, constant: right)
+}
+
+@available(iOS 9.0, *)
+@discardableResult
+public func - (left: SteviaLayoutXAxisAnchor, right: CGFloat) -> SteviaLayoutXAxisAnchor {
+    return SteviaLayoutXAxisAnchor(anchor: left.anchor, constant: -right)
+}
+
+// UILayoutSupport
+
+@available(iOS 9.0, *)
+public extension UILayoutSupport {
+    
+    public var Top: SteviaLayoutYAxisAnchor {
+        return SteviaLayoutYAxisAnchor(anchor: topAnchor)
+    }
+    
+    public var Bottom: SteviaLayoutYAxisAnchor {
+        return SteviaLayoutYAxisAnchor(anchor: bottomAnchor)
+    }
+}
diff --git a/Demo/Source/Stevia+Notifications.swift b/Demo/Source/Stevia+Notifications.swift
new file mode 100644
index 00000000..5fec9875
--- /dev/null
+++ b/Demo/Source/Stevia+Notifications.swift
@@ -0,0 +1,20 @@
+//
+//  Stevia+Notifications.swift
+//  LoginStevia
+//
+//  Created by Sacha Durand Saint Omer on 12/10/15.
+//  Copyright © 2015 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension NSObject {
+    
+    public func on(_ event: String, _ callback:@escaping () -> Void) {
+        _ = NotificationCenter.default.addObserver(forName: NSNotification.Name(rawValue: event),
+                                                                object: nil,
+                                                                queue: nil) { _ in
+            callback()
+        }
+    }
+}
diff --git a/Demo/Source/Stevia+Operators.swift b/Demo/Source/Stevia+Operators.swift
new file mode 100644
index 00000000..b1a4517e
--- /dev/null
+++ b/Demo/Source/Stevia+Operators.swift
@@ -0,0 +1,208 @@
+//
+//  Stevia+Operators.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+prefix operator |
+@discardableResult
+public prefix func | (p: UIView) -> UIView {
+    return p.left(0)
+}
+
+postfix operator |
+@discardableResult
+public postfix func | (p: UIView) -> UIView {
+    return p.right(0)
+}
+
+infix operator ~ : HeightPrecedence
+
+precedencegroup HeightPrecedence {
+    lowerThan: AdditionPrecedence
+}
+
+@discardableResult
+public func ~ (left: UIView, right: CGFloat) -> UIView {
+    return left.height(right)
+}
+
+@discardableResult
+public func ~ (left: UIView, right: SteviaFlexibleMargin) -> UIView {
+    return left.height(right)
+}
+
+@discardableResult
+public func ~ (left: [UIView], right: CGFloat) -> [UIView] {
+    for l in left { l.height(right) }
+    return left
+}
+
+@discardableResult
+public func ~ (left: [UIView], right: SteviaFlexibleMargin) -> [UIView] {
+    for l in left { l.height(right) }
+    return left
+}
+
+prefix operator |-
+@discardableResult
+public prefix func |- (p: CGFloat) -> SideConstraint {
+    var s = SideConstraint()
+    s.constant = p
+    return s
+}
+
+@discardableResult
+public prefix func |- (v: UIView) -> UIView {
+    v.left(8)
+    return v
+}
+
+postfix operator -|
+@discardableResult
+public postfix func -| (p: CGFloat) -> SideConstraint {
+    var s = SideConstraint()
+    s.constant = p
+    return s
+}
+
+@discardableResult
+public postfix func -| (v: UIView) -> UIView {
+    v.right(8)
+    return v
+}
+
+public struct SideConstraint {
+    var constant: CGFloat!
+}
+
+public struct PartialConstraint {
+    var view1: UIView!
+    var constant: CGFloat!
+    var views: [UIView]?
+}
+
+@discardableResult
+public func - (left: UIView, right: CGFloat) -> PartialConstraint {
+    var p = PartialConstraint()
+    p.view1 = left
+    p.constant = right
+    return p
+}
+
+// Side Constraints
+
+@discardableResult
+public func - (left: SideConstraint, right: UIView) -> UIView {
+    if let spv = right.superview {
+        let c = constraint(item: right, attribute: .left,
+                           toItem: spv, attribute: .left,
+                           constant: left.constant)
+        spv.addConstraint(c)
+    }
+    return right
+}
+
+@discardableResult
+public func - (left: [UIView], right: SideConstraint) -> [UIView] {
+    let lastView = left[left.count-1]
+    if let spv = lastView.superview {
+        let c = constraint(item: lastView, attribute: .right,
+                           toItem: spv, attribute: .right,
+                           constant: -right.constant)
+        spv.addConstraint(c)
+    }
+    return left
+}
+
+@discardableResult
+public func - (left: UIView, right: SideConstraint) -> UIView {
+    if let spv = left.superview {
+        let c = constraint(item: left, attribute: .right,
+                           toItem: spv, attribute: .right,
+                           constant: -right.constant)
+        spv.addConstraint(c)
+    }
+    return left
+}
+
+@discardableResult
+public func - (left: PartialConstraint, right: UIView) -> [UIView] {
+    if let views = left.views {
+        if let spv = right.superview {
+            let lastView = views[views.count-1]
+            let c = constraint(item: lastView, attribute: .right,
+                               toItem: right, attribute: .left,
+                               constant: -left.constant)
+            spv.addConstraint(c)
+        }
+        
+        return  views + [right]
+    } else {
+        // were at the end?? nooope?/?
+        if let spv = right.superview {
+            let c = constraint(item: left.view1, attribute: .right,
+                               toItem: right, attribute: .left,
+                               constant: -left.constant)
+            spv.addConstraint(c)
+        }
+        return  [left.view1, right]
+    }
+}
+
+@discardableResult
+public func - (left: UIView, right: UIView) -> [UIView] {
+    if let spv = left.superview {
+        let c = constraint(item: right, attribute: .left,
+                           toItem: left, attribute: .right,
+                           constant: 8)
+        spv.addConstraint(c)
+    }
+    return [left, right]
+}
+
+@discardableResult
+public func - (left: [UIView], right: CGFloat) -> PartialConstraint {
+    var p = PartialConstraint()
+    p.constant = right
+    p.views = left
+    return p
+}
+
+@discardableResult
+public func - (left: [UIView], right: UIView) -> [UIView] {
+    let lastView = left[left.count-1]
+    if let spv = lastView.superview {
+        let c = constraint(item: lastView, attribute: .right,
+                           toItem: right, attribute: .left,
+                           constant: -8)
+        spv.addConstraint(c)
+    }
+    return left + [right]
+}
+
+//// Test space in Horizointal layout ""
+public struct Space {
+    var previousViews: [UIView]!
+}
+
+@discardableResult
+public func - (left: UIView, right: String) -> Space {
+    return Space(previousViews: [left])
+}
+
+@discardableResult
+public func - (left: [UIView], right: String) -> Space {
+    return Space(previousViews: left)
+}
+
+@discardableResult
+public func - (left: Space, right: UIView) -> [UIView] {
+    var va = left.previousViews
+    va?.append(right)
+    return va!
+}
diff --git a/Demo/Source/Stevia+Percentage.swift b/Demo/Source/Stevia+Percentage.swift
new file mode 100644
index 00000000..702cf260
--- /dev/null
+++ b/Demo/Source/Stevia+Percentage.swift
@@ -0,0 +1,175 @@
+//
+//  Stevia+Percentage.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 21/01/2017.
+//  Copyright © 2017 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public struct SteviaPercentage {
+    let value: CGFloat
+}
+
+postfix operator %
+public postfix func % (v: CGFloat) -> SteviaPercentage {
+    return SteviaPercentage(value: v)
+}
+
+public extension UIView {
+    
+    /**
+     Adds an Autolayout constraint for sizing the view.
+     
+     ```
+     image.size(100)
+     image.size(100%)
+     
+     // is equivalent to
+     
+     image.width(100).height(100)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func size(_ p: SteviaPercentage) -> UIView {
+        width(p)
+        height(p)
+        return self
+    }
+    
+    /**
+     Adds an Autolayout constraint for setting the view's width.
+     
+     ```
+     image.width(100)
+     image.width(<=100)
+     image.width(>=100)
+     image.width(100%)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func width(_ p: SteviaPercentage) -> UIView {
+        if let spv = superview {
+            Width == p.value % spv.Width
+        }
+        return self
+    }
+    
+    /**
+     Adds an Autolayout constraint for setting the view's height.
+     
+     ```
+     image.height(100)
+     
+     // is equivalent to
+     
+     image ~ 100
+     
+     // Flexible margins
+     image.height(<=100)
+     image.height(>=100)
+     image.height(100%)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func height(_ p: SteviaPercentage) -> UIView {
+        if let spv = superview {
+            Height == p.value % spv.Height
+        }
+        return self
+    }
+    
+    /** Sets the top margin for a view.
+     
+    Example Usage :
+     
+     label.top(20)
+     label.top(<=20)
+     label.top(>=20)
+     label.top(20%)
+     
+    - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func top(_ p: SteviaPercentage) -> UIView {
+        if let spv = superview {
+            Top == p.value % spv.Bottom
+        }
+        return self
+    }
+    
+    /** Sets the left margin for a view.
+     
+     Example Usage :
+     
+     label.left(20)
+     label.left(<=20)
+     label.left(>=20)
+     label.left(20%)
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func left(_ p: SteviaPercentage) -> UIView {
+        if let spv = superview {
+            Left == p.value % spv.Right
+        }
+        return self
+    }
+    
+    /** Sets the right margin for a view.
+     
+     Example Usage :
+     
+     label.right(20)
+     label.right(<=20)
+     label.right(>=20)
+     label.right(20%)
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func right(_ p: SteviaPercentage) -> UIView {
+        if let spv = superview {
+            if p.value == 100 {
+                Right == spv.Left
+            } else {
+                Right == (100 - p.value) % spv.Right
+            }
+        }
+        return self
+    }
+    
+    /** Sets the bottom margin for a view.
+     
+     Example Usage :
+     
+     label.bottom(20)
+     label.bottom(<=20)
+     label.bottom(>=20)
+     label.bottom(20%)
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func bottom(_ p: SteviaPercentage) -> UIView {
+        if let spv = superview {
+            if p.value == 100 {
+                Bottom == spv.Top
+            } else {
+                Bottom == (100 - p.value) % spv.Bottom
+            }
+        }
+        return self
+    }
+}
diff --git a/Demo/Source/Stevia+Position.swift b/Demo/Source/Stevia+Position.swift
new file mode 100644
index 00000000..79c14002
--- /dev/null
+++ b/Demo/Source/Stevia+Position.swift
@@ -0,0 +1,171 @@
+//
+//  Stevia+Position.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /** Sets the left margin for a view.
+     
+    Example Usage :
+     
+     label.left(20)
+     label.left(<=20)
+     label.left(>=20)
+     label.left(20%)
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func left(_ points: CGFloat) -> UIView {
+        return position(.left, points: points)
+    }
+    
+    /** Sets the right margin for a view.
+     
+    Example Usage :
+     
+     label.right(20)
+     label.right(<=20)
+     label.right(>=20)
+     label.right(20%)
+     
+     - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func right(_ points: CGFloat) -> UIView {
+        return position(.right, points: -points)
+    }
+    
+    /** Sets the top margin for a view.
+     
+    Example Usage :
+     
+     label.top(20)
+     label.top(<=20)
+     label.top(>=20)
+     label.top(20%)
+     
+    - Returns: Itself for chaining purposes
+    */
+    @discardableResult
+    public func top(_ points: CGFloat) -> UIView {
+        return position(.top, points: points)
+    }
+    
+    /** Sets the bottom margin for a view.
+     
+    Example Usage :
+     
+     label.bottom(20)
+     label.bottom(<=20)
+     label.bottom(>=20)
+     label.bottom(20%)
+     
+    - Returns: Itself for chaining purposes
+    */
+    @discardableResult
+    public func bottom(_ points: CGFloat) -> UIView {
+        return position(.bottom, points: -points)
+    }
+
+    /** Sets the left margin for a view.
+     
+    Example Usage :
+     
+     label.left(20)
+     label.left(<=20)
+     label.left(>=20)
+     label.left(20%)
+     
+    - Returns: Itself for chaining purposes
+    */
+    @discardableResult
+    public func left(_ fm: SteviaFlexibleMargin) -> UIView {
+        return position(.left, relatedBy: fm.relation, points: fm.points)
+    }
+    
+    /** Sets the right margin for a view.
+     
+    Example Usage :
+     
+     label.right(20)
+     label.right(<=20)
+     label.right(>=20)
+     label.right(20%)
+     
+    - Returns: Itself for chaining purposes
+    */
+    @discardableResult
+    public func right(_ fm: SteviaFlexibleMargin) -> UIView {
+        // For right this should be inverted.
+        var n = SteviaFlexibleMargin()
+        n.points = -fm.points
+        if fm.relation == .greaterThanOrEqual {
+            n.relation = .lessThanOrEqual
+        }
+        if fm.relation == .lessThanOrEqual {
+            n.relation = .greaterThanOrEqual
+        }
+        return position(.right, relatedBy: n.relation, points: n.points)
+    }
+    
+    /** Sets the top margin for a view.
+     
+    Example Usage :
+     
+     label.top(20)
+     label.top(<=20)
+     label.top(>=20)
+     label.top(20%)
+     
+    - Returns: Itself for chaining purposes
+     */
+    @discardableResult
+    public func top(_ fm: SteviaFlexibleMargin) -> UIView {
+        return position(.top, relatedBy: fm.relation, points: fm.points)
+    }
+    
+    /** Sets the bottom margin for a view.
+     
+    Example Usage :
+     
+     label.bottom(20)
+     label.bottom(<=20)
+     label.bottom(>=20)
+     label.bottom(20%)
+     
+    - Returns: Itself for chaining purposes
+    */
+    @discardableResult
+    public func bottom(_ fm: SteviaFlexibleMargin) -> UIView {
+        // For bottom this should be inverted.
+        var n = SteviaFlexibleMargin()
+        n.points = -fm.points
+        if fm.relation == .greaterThanOrEqual {
+            n.relation = .lessThanOrEqual
+        }
+        if fm.relation == .lessThanOrEqual {
+            n.relation = .greaterThanOrEqual
+        }
+        return position(.bottom, relatedBy: n.relation, points: n.points)
+    }
+    
+    fileprivate func position(_ position: NSLayoutConstraint.Attribute,
+                              relatedBy: NSLayoutConstraint.Relation = .equal,
+                              points: CGFloat) -> UIView {
+        if let spv = superview {
+            let c = constraint(item: self, attribute: position,
+                               relatedBy: relatedBy,
+                               toItem: spv,
+                               constant: points)
+            spv.addConstraint(c)
+        }
+        return self
+    }
+}
diff --git a/Demo/Source/Stevia+Size.swift b/Demo/Source/Stevia+Size.swift
new file mode 100644
index 00000000..987e924e
--- /dev/null
+++ b/Demo/Source/Stevia+Size.swift
@@ -0,0 +1,279 @@
+//
+//  Stevia+Size.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /**
+     Adds an Autolayout constraint for sizing the view.
+     
+     ```
+     image.size(100)
+     image.size(100%)
+     
+     // is equivalent to
+     
+     image.width(100).height(100)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func size(_ points: CGFloat) -> UIView {
+        width(points)
+        height(points)
+        return self
+    }
+    
+    /**
+     Adds an Autolayout constraint for setting the view's height.
+     
+     ```
+     image.height(100)
+     
+     // is equivalent to
+     
+     image ~ 100
+     
+     // Flexible margins
+     image.height(<=100)
+     image.height(>=100)
+     image.height(100%)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func height(_ points: CGFloat) -> UIView {
+        return size(.height, points: points)
+    }
+    
+    /**
+     Adds an Autolayout constraint for setting the view's width.
+     
+     ```
+     image.width(100)
+     image.width(<=100)
+     image.width(>=100)
+     image.width(100%)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func width(_ points: CGFloat) -> UIView {
+        return size(.width, points: points)
+    }
+    
+    /**
+     Adds an Autolayout constraint for setting the view's height.
+     
+     ```
+     image.height(100)
+     
+     // is equivalent to
+     
+     image ~ 100
+     
+     // Flexible margins
+     image.height(<=100)
+     image.height(>=100)
+     image.height(100%)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func height(_ fm: SteviaFlexibleMargin) -> UIView {
+        return size(.height, relatedBy: fm.relation, points: fm.points)
+    }
+    
+    /**
+     Adds an Autolayout constraint for setting the view's width.
+     
+     ```
+     image.width(100)
+     image.width(<=100)
+     image.width(>=100)
+     image.width(100%)
+     ```
+     
+     - Returns: Itself, enabling chaining,
+     
+     */
+    @discardableResult
+    public func width(_ fm: SteviaFlexibleMargin) -> UIView {
+        return size(.width, relatedBy: fm.relation, points: fm.points)
+    }
+    
+    fileprivate func size(_ attribute: NSLayoutConstraint.Attribute,
+                          relatedBy: NSLayoutConstraint.Relation = .equal,
+                          points: CGFloat) -> UIView {
+        let c = constraint(item: self,
+                           attribute: attribute,
+                           relatedBy: relatedBy,
+                           constant: points)
+        if let spv = superview {
+            spv.addConstraint(c)
+        } else {
+            addConstraint(c)
+        }
+        return self
+    }
+}
+
+/**
+ Enforces an array of views to keep the same size.
+ 
+ ```
+ equal(sizes: image1, image2, image3)
+ ```
+ 
+ - Returns: The views enabling chaining.
+ 
+ */
+@discardableResult
+public func equal(sizes views: UIView...) -> [UIView] {
+    return equal(sizes: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed:"equal(sizes:)")
+@discardableResult
+public func equalSizes(_ views: UIView...) -> [UIView] {
+    return equal(sizes: views)
+}
+
+/**
+ Enforces an array of views to keep the same size.
+ 
+ ```
+ equal(sizes: image1, image2, image3)
+ ```
+ 
+ - Returns: The views enabling chaining.
+ 
+ */
+@discardableResult
+public func equal(sizes views: [UIView]) -> [UIView] {
+    equal(heights: views)
+    equal(widths: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed:"equal(sizes:)")
+@discardableResult
+public func equalSizes(_ views: [UIView]) -> [UIView] {
+    equal(heights: views)
+    equal(widths: views)
+    return views
+}
+
+/**
+ Enforces an array of views to keep the same widths.
+ 
+ ```
+ equal(widths: image1, image2, image3)
+ ```
+ 
+ - Returns: The views enabling chaining.
+ 
+ */
+@discardableResult
+public func equal(widths views: UIView...) -> [UIView] {
+    return equal(widths: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed:"equal(widths:)")
+@discardableResult
+public func equalWidths(_ views: UIView...) -> [UIView] {
+    return equal(widths: views)
+}
+
+/**
+ Enforces an array of views to keep the same widths.
+ 
+ ```
+ equal(widths: image1, image2, image3)
+ ```
+ 
+ - Returns: The views enabling chaining.
+ 
+ */
+@discardableResult
+public func equal(widths views: [UIView]) -> [UIView] {
+    equal(.width, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed:"equal(widths:)")
+@discardableResult
+public func equalWidths(_ views: [UIView]) -> [UIView] {
+    equal(.width, views: views)
+    return views
+}
+
+/**
+ Enforces an array of views to keep the same heights.
+ 
+ ```
+ equal(heights: image1, image2, image3)
+ ```
+ 
+ - Returns: The views enabling chaining.
+ 
+ */
+@discardableResult
+public func equal(heights views: UIView...) -> [UIView] {
+    return equal(heights: views)
+}
+
+@available(*, deprecated: 4.1.0, renamed:"equal(heights:)")
+@discardableResult
+public func equalHeights(_ views: UIView...) -> [UIView] {
+    return equal(heights: views)
+}
+
+/**
+ Enforces an array of views to keep the same heights.
+ 
+ ```
+ equal(heights: image1, image2, image3)
+ ```
+ 
+ - Returns: The views enabling chaining.
+ 
+ */
+@discardableResult
+public func equal(heights views: [UIView]) -> [UIView] {
+    equal(.height, views: views)
+    return views
+}
+
+@available(*, deprecated: 4.1.0, renamed:"equal(heights:)")
+@discardableResult
+public func equalHeights(_ views: [UIView]) -> [UIView] {
+    equal(.height, views: views)
+    return views
+}
+
+private func equal(_ attribute: NSLayoutConstraint.Attribute, views: [UIView]) {
+    var previousView: UIView?
+    for v in views {
+        if let pv = previousView {
+            if let spv = v.superview {
+                spv.addConstraint(item: v, attribute: attribute, toItem: pv)
+            }
+        }
+        previousView = v
+    }
+}
diff --git a/Demo/Source/Stevia+Stacks.swift b/Demo/Source/Stevia+Stacks.swift
new file mode 100644
index 00000000..23820ebc
--- /dev/null
+++ b/Demo/Source/Stevia+Stacks.swift
@@ -0,0 +1,162 @@
+//
+//  Stevia+Stacks.swift
+//  Stevia
+//
+//  Created by Sacha Durand Saint Omer on 10/02/16.
+//  Copyright © 2016 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIView {
+    
+    /**
+     
+     Lays out the views on both axis.
+     
+     Note that this is not needed for Horizontal only layouts.
+     
+     `layout` is primarily for laying out views vertically but horizontal statements 
+     are supported, making it perfect for describing a layout in one single statement.
+     
+     ```
+     layout(
+     100,
+     |-email-| ~ 80,
+     8,
+     |-password-forgot-| ~ 80,
+     >=20,
+     |login| ~ 80,
+     0
+     )
+     ```
+     */
+    @discardableResult
+    public func layout(_ objects: Any...) -> [UIView] {
+        return layout(objects)
+    }
+    
+    @discardableResult
+    public func layout(_ objects: [Any]) -> [UIView] {
+        var previousMargin: CGFloat?
+        var previousFlexibleMargin: SteviaFlexibleMargin?
+        
+        for (i, o) in objects.enumerated() {
+            
+            func viewLogic(_ v: UIView) {
+                if let pm = previousMargin {
+                    if i == 1 {
+                        v.top(pm) // only if first view
+                    } else {
+                        if let vx = objects[i-2] as? UIView {
+                            vx.stackV(m: pm, v: v)
+                        } else if let va = objects[i-2] as? [UIView] {
+                            va.first!.stackV(m: pm, v: v)
+                        }
+                    }
+                    previousMargin = nil
+                } else if let pfm = previousFlexibleMargin {
+                    if i == 1 {
+                        v.top(pfm) // only if first view
+                    } else {
+                        if let vx = objects[i-2] as? UIView {
+                            addConstraint(
+                                item: v, attribute: .top,
+                                relatedBy: pfm.relation,
+                                toItem: vx, attribute: .bottom,
+                                multiplier: 1, constant: pfm.points
+                            )
+                        } else if let va = objects[i-2] as? [UIView] {
+                            addConstraint(
+                                item: v, attribute: .top,
+                                relatedBy: pfm.relation,
+                                toItem: va.first!, attribute: .bottom,
+                                multiplier: 1, constant: pfm.points
+                            )
+                        }
+                    }
+                    previousFlexibleMargin = nil
+                } else {
+                    tryStackViewVerticallyWithPreviousView(v, index: i, objects: objects)
+                }
+            }
+            
+            switch o {
+            case let v as UIView:
+                viewLogic(v)
+            case is Int, is Double, is CGFloat:
+                let m = cgFloatMarginFromObject(o)
+                previousMargin = m // Store margin for next pass
+                if i != 0 && i == (objects.count - 1) {
+                    //Last Margin, Bottom
+                    if let previousView = objects[i-1] as? UIView {
+                        previousView.bottom(m)
+                    } else if let va = objects[i-1] as? [UIView] {
+                        va.first!.bottom(m)
+                    }
+                }
+            case let fm as SteviaFlexibleMargin:
+                previousFlexibleMargin = fm // Store margin for next pass
+                if i != 0 && i == (objects.count - 1) {
+                    //Last Margin, Bottom
+                    if let previousView = objects[i-1] as? UIView {
+                        previousView.bottom(fm)
+                    } else if let va = objects[i-1] as? [UIView] {
+                        va.first!.bottom(fm)
+                    }
+                }
+            case _ as String:() //Do nothin' !
+            case let a as [UIView]:
+                align(horizontally: a)
+                let v = a.first!
+                viewLogic(v)
+            default: ()
+            }
+        }
+        return objects.map {$0 as? UIView }.compactMap {$0}
+    }
+    
+    fileprivate func cgFloatMarginFromObject(_ o: Any) -> CGFloat {
+        var m: CGFloat = 0
+        if let i = o as? Int {
+            m = CGFloat(i)
+        } else if let d = o as? Double {
+            m = CGFloat(d)
+        } else if let cg = o as? CGFloat {
+            m = cg
+        }
+        return m
+    }
+    
+    fileprivate func tryStackViewVerticallyWithPreviousView(_ view: UIView,
+                                                            index: Int, objects: [Any]) {
+        if let pv = previousViewFromIndex(index, objects: objects) {
+            pv.stackV(v: view)
+        }
+    }
+    
+    fileprivate func previousViewFromIndex(_ index: Int, objects: [Any]) -> UIView? {
+        if index != 0 {
+            if let previousView = objects[index-1] as? UIView {
+                return previousView
+            }
+        }
+        return nil
+    }
+    
+    @discardableResult
+    fileprivate func stackV(m points: CGFloat = 0, v: UIView) -> UIView {
+        return stack(.vertical, points: points, v: v)
+    }
+    
+    fileprivate func stack(_ axis: NSLayoutConstraint.Axis,
+                           points: CGFloat = 0, v: UIView) -> UIView {
+        let a: NSLayoutConstraint.Attribute = axis == .vertical ? .top : .left
+        let b: NSLayoutConstraint.Attribute = axis == .vertical ? .bottom : .right
+        if let spv = superview {
+            let c = constraint(item: v, attribute: a, toItem: self, attribute: b, constant: points)
+            spv.addConstraint(c)
+        }
+        return v
+    }
+}
diff --git a/Demo/Source/Stevia+Style.swift b/Demo/Source/Stevia+Style.swift
new file mode 100644
index 00000000..de559cf0
--- /dev/null
+++ b/Demo/Source/Stevia+Style.swift
@@ -0,0 +1,43 @@
+//
+//  Stevia+Style.swift
+//  LoginStevia
+//
+//  Created by Sacha Durand Saint Omer on 01/10/15.
+//  Copyright © 2015 Sacha Durand Saint Omer. All rights reserved.
+//
+
+import UIKit
+
+public extension UIAppearance {
+    
+    /** Applies a styling block on an element.
+     
+    Example Usage:
+     
+    ```
+    button.style { b in
+        b.A = X
+        b.B = Y
+        b.C = Z
+    }
+    ```
+     
+    Handy for reusing styles :
+    ```
+    button.style(buttonStyle)
+
+    // later
+    func buttonStyle(b: UIButton) {
+     ..styling code
+    }
+    ```
+     
+    - Returns: Itself for chaining purposes
+     
+     */
+    @discardableResult
+    public func style(_ styleClosure: (Self) -> Void) -> Self {
+        styleClosure(self)
+        return self
+    }
+}
diff --git a/SwiftMessages/Resources/TestView.xib b/SwiftMessages/Resources/TestView.xib
new file mode 100644
index 00000000..c5f6f878
--- /dev/null
+++ b/SwiftMessages/Resources/TestView.xib
@@ -0,0 +1,124 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14460.31" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" colorMatched="YES">
+    <device id="retina4_7" orientation="portrait">
+        <adaptation id="fullscreen"/>
+    </device>
+    <dependencies>
+        <deployment version="2304" identifier="iOS"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14460.20"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <objects>
+        <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>
+        <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
+        <view contentMode="scaleToFill" id="uEa-1P-F1Y" userLabel="Card View" customClass="TestView" customModule="Demo" customModuleProvider="target">
+            <rect key="frame" x="0.0" y="0.0" width="600" height="150"/>
+            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+            <subviews>
+                <view contentMode="scaleToFill" translatesAutoresizingMaskIntoConstraints="NO" id="A7b-0a-fJG" userLabel="Corner rounding view" customClass="CornerRoundingView" customModule="Demo" customModuleProvider="target">
+                    <rect key="frame" x="20" y="0.0" width="560" height="150"/>
+                    <subviews>
+                        <stackView opaque="NO" contentMode="scaleToFill" alignment="center" spacing="10" translatesAutoresizingMaskIntoConstraints="NO" id="SU0-uJ-4pP" userLabel="Content view">
+                            <rect key="frame" x="20" y="20" width="520" height="110"/>
+                            <subviews>
+                                <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="252" verticalHuggingPriority="251" horizontalCompressionResistancePriority="752" text="😬" textAlignment="center" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="T1i-ce-9y8" userLabel="Icon label">
+                                    <rect key="frame" x="0.0" y="32.5" width="43" height="45.5"/>
+                                    <accessibility key="accessibilityConfiguration">
+                                        <bool key="isElement" value="NO"/>
+                                    </accessibility>
+                                    <fontDescription key="fontDescription" type="system" pointSize="38"/>
+                                    <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+                                    <nil key="highlightedColor"/>
+                                </label>
+                                <imageView clipsSubviews="YES" userInteractionEnabled="NO" contentMode="center" horizontalHuggingPriority="252" verticalHuggingPriority="251" horizontalCompressionResistancePriority="752" image="errorIcon" translatesAutoresizingMaskIntoConstraints="NO" id="RxA-tv-YM7" userLabel="Icon image view">
+                                    <rect key="frame" x="53" y="38" width="33" height="34"/>
+                                </imageView>
+                                <stackView opaque="NO" contentMode="scaleToFill" axis="vertical" alignment="top" translatesAutoresizingMaskIntoConstraints="NO" id="i9r-ex-CgT">
+                                    <rect key="frame" x="96" y="36" width="357" height="38.5"/>
+                                    <subviews>
+                                        <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" verticalCompressionResistancePriority="751" text="[Title]" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="8HR-oh-U9F">
+                                            <rect key="frame" x="0.0" y="0.0" width="48.5" height="20.5"/>
+                                            <accessibility key="accessibilityConfiguration">
+                                                <bool key="isElement" value="NO"/>
+                                            </accessibility>
+                                            <fontDescription key="fontDescription" style="UICTFontTextStyleHeadline"/>
+                                            <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+                                            <nil key="highlightedColor"/>
+                                        </label>
+                                        <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="[Message Body]" textAlignment="natural" lineBreakMode="tailTruncation" numberOfLines="0" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="9oc-qg-igL">
+                                            <rect key="frame" x="0.0" y="20.5" width="112" height="18"/>
+                                            <color key="backgroundColor" red="0.0" green="0.0" blue="0.0" alpha="0.0" colorSpace="custom" customColorSpace="sRGB"/>
+                                            <accessibility key="accessibilityConfiguration">
+                                                <bool key="isElement" value="NO"/>
+                                            </accessibility>
+                                            <fontDescription key="fontDescription" style="UICTFontTextStyleSubhead"/>
+                                            <color key="textColor" red="0.0" green="0.0" blue="0.0" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+                                            <nil key="highlightedColor"/>
+                                        </label>
+                                    </subviews>
+                                    <color key="backgroundColor" red="0.0" green="0.0" blue="0.0" alpha="0.0" colorSpace="custom" customColorSpace="sRGB"/>
+                                </stackView>
+                                <button opaque="NO" contentMode="scaleToFill" horizontalHuggingPriority="252" horizontalCompressionResistancePriority="752" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="CxK-Y3-nSI">
+                                    <rect key="frame" x="463" y="40" width="57" height="30"/>
+                                    <fontDescription key="fontDescription" style="UICTFontTextStyleSubhead"/>
+                                    <state key="normal" title="[Button]"/>
+                                </button>
+                            </subviews>
+                        </stackView>
+                    </subviews>
+                    <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+                    <constraints>
+                        <constraint firstAttribute="trailing" secondItem="SU0-uJ-4pP" secondAttribute="trailing" constant="20" id="QN2-NH-rWA"/>
+                        <constraint firstItem="SU0-uJ-4pP" firstAttribute="top" secondItem="A7b-0a-fJG" secondAttribute="top" constant="20" id="S9l-zM-0wc"/>
+                        <constraint firstAttribute="bottom" secondItem="SU0-uJ-4pP" secondAttribute="bottom" constant="20" id="YMg-LN-n7f"/>
+                        <constraint firstItem="SU0-uJ-4pP" firstAttribute="leading" secondItem="A7b-0a-fJG" secondAttribute="leading" constant="20" id="nYJ-Ok-uhC"/>
+                    </constraints>
+                    <userDefinedRuntimeAttributes>
+                        <userDefinedRuntimeAttribute type="number" keyPath="cornerRadius">
+                            <real key="value" value="15"/>
+                        </userDefinedRuntimeAttribute>
+                    </userDefinedRuntimeAttributes>
+                </view>
+            </subviews>
+            <color key="backgroundColor" red="0.0" green="0.0" blue="0.0" alpha="0.0" colorSpace="custom" customColorSpace="sRGB"/>
+            <constraints>
+                <constraint firstAttribute="trailingMargin" secondItem="A7b-0a-fJG" secondAttribute="trailing" priority="900" id="O6e-Yz-cwK"/>
+                <constraint firstItem="A7b-0a-fJG" firstAttribute="leading" secondItem="uEa-1P-F1Y" secondAttribute="leadingMargin" priority="900" id="RiR-2q-ZY5"/>
+                <constraint firstItem="A7b-0a-fJG" firstAttribute="centerX" secondItem="uEa-1P-F1Y" secondAttribute="centerX" priority="950" id="jLv-ud-1WD"/>
+                <constraint firstItem="A7b-0a-fJG" firstAttribute="top" secondItem="uEa-1P-F1Y" secondAttribute="topMargin" id="yAH-C4-oUg"/>
+                <constraint firstAttribute="bottomMargin" secondItem="A7b-0a-fJG" secondAttribute="bottom" id="ygs-aa-zj3"/>
+            </constraints>
+            <freeformSimulatedSizeMetrics key="simulatedDestinationMetrics"/>
+            <userDefinedRuntimeAttributes>
+                <userDefinedRuntimeAttribute type="number" keyPath="bounceAnimationOffset">
+                    <real key="value" value="0.0"/>
+                </userDefinedRuntimeAttribute>
+                <userDefinedRuntimeAttribute type="number" keyPath="topLayoutMarginAddition">
+                    <real key="value" value="10"/>
+                </userDefinedRuntimeAttribute>
+                <userDefinedRuntimeAttribute type="number" keyPath="leftLayoutMarginAddition">
+                    <real key="value" value="10"/>
+                </userDefinedRuntimeAttribute>
+                <userDefinedRuntimeAttribute type="number" keyPath="bottomLayoutMarginAddition">
+                    <real key="value" value="10"/>
+                </userDefinedRuntimeAttribute>
+                <userDefinedRuntimeAttribute type="number" keyPath="rightLayoutMarginAddition">
+                    <real key="value" value="10"/>
+                </userDefinedRuntimeAttribute>
+                <userDefinedRuntimeAttribute type="boolean" keyPath="collapseLayoutMarginAdditions" value="YES"/>
+            </userDefinedRuntimeAttributes>
+            <connections>
+                <outlet property="backgroundView" destination="A7b-0a-fJG" id="R1k-6D-zIA"/>
+                <outlet property="bodyLabel" destination="9oc-qg-igL" id="ebS-73-kbp"/>
+                <outlet property="button" destination="CxK-Y3-nSI" id="csj-uy-rHl"/>
+                <outlet property="iconImageView" destination="RxA-tv-YM7" id="w6j-4o-RnC"/>
+                <outlet property="iconLabel" destination="T1i-ce-9y8" id="XiD-0J-kdm"/>
+                <outlet property="titleLabel" destination="8HR-oh-U9F" id="Zbb-wl-ubV"/>
+            </connections>
+            <point key="canvasLocation" x="484" y="387"/>
+        </view>
+    </objects>
+    <resources>
+        <image name="errorIcon" width="33" height="34"/>
+    </resources>
+</document>