style.css

body{
  font-family: 'Josefin Sans', sans-serif;
  background: url(./media/grass.png);
  background-color: white;
  box-sizing: border-box;
  padding: 0;
  margin: 0;
  display: grid;
  place-items: center;
}

*, *::before, *::after {
  box-sizing: inherit;
}

#container{ 
  width: 90%;
  max-width: 600px;
  height: 95vh;
  margin-top: 1rem;
  background-color: rgba(256, 256, 256, 0.6);
  border: 5px solid black;
  display: flex;
  flex-direction: column;
  align-items: center;
}

header{
  text-align: center;
}

#score{
  padding: 1rem;
}

#play-area{
  width: 100%;
  height: 100%;
  display: flex;
  flex-wrap: wrap;
}

.box{
  background: transparent;
  flex: 1 0 33.33%;
  border: 5px solid transparent;
  position: relative;
  overflow: hidden;
}

.box:after{
  display: block;
  background: burlywood;
  background-size: contain;
  border: 3px dotted #795548;
  content: '';
  width: 100%;
  height: 45px;
  position: absolute;
  z-index: 2;
  bottom: 0px;
}

.cat {
  background: url(./media/cat2.svg) center no-repeat;
  background-size: contain;
  position: absolute;
  z-index: 1;
  width: 100%;
  height: 100px;
  top: 100%;
  transition: all 0.4s;
}

.box.up .cat{
  top: 5%;
}

button{
  font-family: 'Josefin Sans', sans-serif;
  padding: 8px 64px;
  background-color: transparent;
  border: 2px solid black;
  margin: 1rem 0 0.5rem 0;
}

button:hover{
  background-color: black;
  color: white;
  transition: ease 0.5s;
}