Hovered gradient button

by Julien Roche

HTML

<button class="button" style="width: 400px;">Hover me !!</button>

CSS

/** Use of CSS variables */
.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;
}

.button 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;
}

Babel + JSX

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`)

};