.button {
position: relative;
appearance: none;
background: #f72359;
padding: 1em 2em;
border: none;
color: white;
font-size: 1.2em;
cursor: pointer;
outline: none;
overflow: hidden;
border-radius: 100px;
}
span {
position: relative;
}
.button:before {
--size: 0;
content: '';
position: absolute;
left: var(--x);
top: var(--y);
width: var(--size);
height: var(--size);
background: radial-gradient(circle closest-side, #4405f7, transparent);
transform: translate(-50%, -50%);
transition: width .2s ease, height .2s ease;
}
.button:hover:before {
--size: 400px;
}
document.querySelector('.button').onmousemove = (e) => {
const x = e.pageX-e.target.offsetLeft;
const y = e.pageY-e.target.offsetTop;
e.target.style.setProperty('--x', `${ x }px`)
e.target.style.setProperty('--y', `${ y }px`)
}
