<a href="#" class="button instagram"><span class="gradient"></span>Sign Up</a>

body {
	display: flex;
	justify-content: center;
	align-items: center;
}

body {
	width: 100%;
	height: 90vh;
}

.button {
	display: block;
  width: 320px;
  max-width: 100%;
  margin: 0 auto;
  margin-bottom: 0;
  overflow: hidden;
  position: relative;
  transform: translatez(0);
  text-decoration: none;
  box-sizing: border-box;
  font-size: 24px;
	font-weight: normal;
	box-shadow: 0 9px 18px rgba(0,0,0,0.2);
}

.instagram {
	text-align: center;
	border-radius: 50px;
  padding: 26px;
  color: white;
  background: #BD3381;
  transition: all 0.2s ease-out 0s;
}

.gradient {
	display: block;
  position: absolute;
  top: 0;
  right: 0;
  width: 100%;
  height: 100%;
  bottom: auto;
  margin: auto;
  z-index: -1;
  background: radial-gradient(90px circle at top center, rgba(238,88,63,.8) 30%, rgba(255,255,255,0));
  transition: all 0s ease-out 0s;
	transform: translatex(-140px);
	animation: 18s linear 0s infinite move;
}

@keyframes move {
	0% {
		transform: translatex(-140px);
	}
	25% {
		transform: translatex(140px);
		opacity: 0.3;
	}
	50% {
		transform: translatex(140px);
		opacity: 1;
		background: radial-gradient(90px circle at bottom center, rgba(238,88,63,.5) 30%, rgba(255,255,255,0));
	}
	75% {
		transform: translatex(-140px);
		opacity: 0.3;
	}
	100% {
		opacity: 1;
		transform: translatex(-140px);
		background: radial-gradient(90px circle at top center, rgba(238,88,63,.5) 30%, rgba(255,255,255,0));
	}
}