style.css

*{
    padding: 0;
    margin: 0;
    box-sizing: border-box;
    font-family: sans-serif;
}

body{
    width: 100%;
    height: 100vh;
    background-color: #1C1C1C;
    display: flex;
    justify-content: center;
    align-items: center;
}

.btn{
    display: block;
    text-decoration: none;
    text-transform: uppercase;
    font-size: 10px;
    font-weight: bold;
    color: #FF00FF;
    margin: 0 15px;


    padding: 10px 35px;

    border: 2px solid #ADFF2F;
}

.btn:hover
{
    color: white;
}

.btn::before{
    content: "";
    position: absolute;
    top: 0;
    left:0;
    width: 100%;
    height: 100;
    background: rgb(0, 165, 124);
    z-index: -1;
    border-radius: 0 0 50% 50%;
    height: 0%;
    transition: all 0.5s;
}

.btn1:hover::before{
    height: 190%;
    width: 100%;
}

.btn2:hover::before{
    height: 190%;
    width: 100%;
}


.btn3:hover::before{
    height: 190%;
    width: 100%;
    transform: translate(-50%, -50%) rotate(45deg);
}

.btn4:hover::before{
    height: 190%;
    width: 100%;
    border-radius: 50%;
}