<a href="https://it-a1.ru/#">
  <button>
    <span>кнопочка</span>
  </button>
</a>

<a href="https://vk.com/man_andrey">
  <button>
    <span>Попочка</span>
  </button>
</a>

<a href="https://vk.com/it_a1">
  <button>
    <span>Жопочка</span>
  </button>
</a>

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

:root {
  --x: 0;
  --y: 0;
  --xp: 0;
  --yp: 0;
	--hue: calc(0 + (var(--xp) * 500));
	--bg: hsl(0 0% 10%);
	--size: 100px;
	--glow: radial-gradient(
			50% 50% at center,
			hsl(var(--hue) 80% 85%),
			hsl(var(--hue) 80% 70%),
			transparent
		)
		calc((var(--x) * 1px) - (var(--size) * 0.5))
		calc((var(--y) * 1px) - (var(--size) * 0.5)) / var(--size) var(--size) no-repeat fixed;
}

.controls {
  position: fixed;
  top: 2rem;
  right: 2rem;
}

body {
	display: flex;
	place-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  justify-content: center;
	min-height: 100vh;
	font-family:  "SF Pro Text", "SF Pro Icons", "AOS Icons", "Helvetica Neue", Helvetica, Arial, sans-serif, system-ui;
	background: var(--bg);
}

button {
	border-radius: 1rem;
	text-transform: uppercase;
	font-weight: bold;
	letter-spacing: 0.1ch;
	background: var(--bg);
	border: 4px solid transparent;
	box-shadow: 0 1px hsl(0 0% 100% / 0.15) inset;
	cursor: pointer;
	background:
		linear-gradient(var(--bg), var(--bg)) padding-box,
		var(--glow),
		linear-gradient(black, black) border-box;
	transition: background-size 0.24s;
  touch-action: none;
  position: relative;
	padding: 1rem 2rem;
}

button::before {
  content: "";
  position: absolute;
  inset: 0;
  box-shadow: 0 1px hsl(0 0% 100% / 0.15) inset;
  background: var(--bg);
  z-index: 2;
/*   border: 4px solid transparent; */
  border-radius: 1rem;
}

button span {
	background: var(--glow), black;
	background-clip: text;
	color: transparent;
  height: 100%;
  width: 100%;
  z-index: 2;
  position: relative;
  inset: 0;
}

:root:has(button:active) {
	--size: 300px;
}

button::after {
  content: "";
  position: absolute;
  inset: -4px;
  filter: blur(20px);
  border: 4px solid transparent;
  background: var(--glow);
  border-radius: 1rem;
}

const syncPointer = ({ x: pointerX, y: pointerY }) => {
  const x = pointerX.toFixed(2)
  const y = pointerY.toFixed(2)
  const xp = (pointerX / window.innerWidth).toFixed(2)
  const yp = (pointerY / window.innerHeight).toFixed(2)
  document.documentElement.style.setProperty('--x', x)
  document.documentElement.style.setProperty('--xp', xp)
  document.documentElement.style.setProperty('--y', y)
  document.documentElement.style.setProperty('--yp', yp)
}
document.body.addEventListener('pointermove', syncPointer)