30-seconds-of-code/snippets/mouse-cursor-gradient-tracking.md

title, type, tags, cover, dateModified

title	type	tags	cover	dateModified
Mouse cursor gradient tracking	snippet	visual interactivity	tram-car	2021-01-07T23:52:15+02:00

A hover effect where the gradient follows the mouse cursor.

• Declare two CSS variables, --x and --y, used to track the position of the mouse on the button.
• Declare a CSS variable, --size, used to modify the gradient's dimensions.
• Use background: radial-gradient(circle closest-side, pink, transparent) to create the gradient at the correct position.
• Use Document.querySelector() and EventTarget.addEventListener() to register a handler for the 'mousemove' event.
• Use Element.getBoundingClientRect() and CSSStyleDeclaration.setProperty() to update the values of the --x and --y CSS variables.

<button class="mouse-cursor-gradient-tracking">
  <span>Hover me</span>
</button>

.mouse-cursor-gradient-tracking {
  position: relative;
  background: #7983ff;
  padding: 0.5rem 1rem;
  font-size: 1.2rem;
  border: none;
  color: white;
  cursor: pointer;
  outline: none;
  overflow: hidden;
}

.mouse-cursor-gradient-tracking span {
  position: relative;
}

.mouse-cursor-gradient-tracking::before {
  --size: 0;
  content: '';
  position: absolute;
  left: var(--x);
  top: var(--y);
  width: var(--size);
  height: var(--size);
  background: radial-gradient(circle closest-side, pink, transparent);
  transform: translate(-50%, -50%);
  transition: width 0.2s ease, height 0.2s ease;
}

.mouse-cursor-gradient-tracking:hover::before {
  --size: 200px;
}

let btn = document.querySelector('.mouse-cursor-gradient-tracking');
btn.addEventListener('mousemove', e => {
  let rect = e.target.getBoundingClientRect();
  let x = e.clientX - rect.left;
  let y = e.clientY - rect.top;
  btn.style.setProperty('--x', x + 'px');
  btn.style.setProperty('--y', y + 'px');
});