<button class="shiny">Let in shiiine 🎶</button>
body {
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
  height: 100vh;
}

.shiny {
  color: white;
  position: relative;
  border: none;
  padding: 10px 15px;
  background: #3984ff;
  border-radius: 10px;
  font-weight: bold;
  cursor: pointer;
  overflow: hidden;
}

.shiny::after {
  content: "";
  position: absolute;
  top: calc(var(--y, 0) * 1px - 50px);
  left: calc(var(--x, 0) * 1px - 50px);
  width: 100px;
  height: 100px;
  background: radial-gradient(white, #3984ff00 80%);

  opacity: 0;
  transition: opacity 0.2s;
}

.shiny:hover::after {
  opacity: 0.4;
}

const button = document.querySelector(".shiny");

const readout = document.querySelector("p");

button.addEventListener("mousemove", (e) => {
  const { x, y } = button.getBoundingClientRect();
  button.style.setProperty("--x", e.clientX - x);
  button.style.setProperty("--y", e.clientY - y);
});

External CSS

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External JavaScript

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