<button>Let's Go !</button>

@import url("https://fonts.googleapis.com/css2?family=Exo:wght@600&display=swap");

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  width: 100vw;
  min-height: 100vh;
  font-family: "Exo", Arial, sans-serif;
  background-color: rgb(237 242 247);
  padding: 20px;

  display: grid;
  place-content: center;
}

:root {
  --purple: #7f00ff;
  --pink: #e100ff;
}

button {
  display: inline-flex;
  justify-content: center;
  align-items: center;
  position: relative;
  outline: none;
  border: none;
  font-family: "Exo", Arial, sans-serif;
  -webkit-appearance: none;
  -webkit-tap-highlight-color: transparent;
  cursor: pointer;
  user-select: none;
  padding: 1em 2em;
  border-radius: 50px;
  color: #fff;
  min-width: 20vw;
  font-size: 2rem;

  background: linear-gradient(to right, var(--purple), var(--pink));
}

button::after {
  content: "";
  position: absolute;
  z-index: -1;
  inset: 0;
  opacity: 0.8;
  border-radius: 10rem;
  background: inherit;
  filter: blur(30px);

  transition: all 0.2s;
}

button:hover::after {
  filter: blur(32px);
  bottom: -5px;
}

button:hover:active::after {
  filter: blur(10px);
  bottom: -6px;
}