Shimmering animated border gradient effect in CSS

index.html

<button>
	<div>
		A beautiful button
	</div>
</button>

shimmering-animated-border-gradient-effect-in-css.markdown

Shimmering animated border gradient effect in CSS

An exploration of animated multi-color conic gradients to create button border animation effects.

A Pen by João Bosco Dos Reis Becker on CodePen.

License.

style.css

/* The secret sauce that enables gradient rotation. NOTE: does not work in all browsers. https://caniuse.com/?search=%40property */
@property --border-angle-1 {
	syntax: "<angle>";
	inherits: true;
	initial-value: 0deg;
}

@property --border-angle-2 {
	syntax: "<angle>";
	inherits: true;
	initial-value: 90deg;
}

@property --border-angle-3 {
	syntax: "<angle>";
	inherits: true;
	initial-value: 180deg;
}


/* sRGB color. */
:root {
	--bright-blue: rgb(0, 100, 255);
	--bright-green: rgb(0, 255, 0);
	--bright-red: rgb(255, 0, 0);
	--background: black;
	--foreground: white;
	--border-size: 2px;
	--border-radius: 0.75em;
}

/* Display-P3 color, when supported. */
@supports (color: color(display-p3 1 1 1)) {
	:root {
		--bright-blue: color(display-p3 0 0.2 1);
		--bright-green: color(display-p3 0.4 1 0);
		--bright-red: color(display-p3 1 0 0);
	}
}

@keyframes rotateBackground {
	to { --border-angle-1: 360deg; }
}

@keyframes rotateBackground2 {
	to { --border-angle-2: -270deg; }
}

@keyframes rotateBackground3 {
	to { --border-angle-3: 540deg; }
}

body {
	background: var(--background);
	color: var(--foreground);
	min-height: 100dvh;
	display: grid;
	place-content: center;
	margin: 0;
	font-family: "Aspekta";
}

button {
	--border-angle-1: 0deg;
	--border-angle-2: 90deg;
	--border-angle-3: 180deg;
	color: inherit;
	font-size: calc(0.8rem + 4vmin);
	font-family: inherit;
	border: 0;
	padding: var(--border-size);
	display: flex;
	width: max-content;
	border-radius: var(--border-radius);
	background-color: transparent;
	background-image: conic-gradient(
			from var(--border-angle-1) at 10% 15%,
			transparent,
			var(--bright-blue) 10%,
			transparent 30%,
			transparent
		),
		conic-gradient(
			from var(--border-angle-2) at 70% 60%,
			transparent,
			var(--bright-green) 10%,
			transparent 60%,
			transparent
		),
		conic-gradient(
			from var(--border-angle-3) at 50% 20%,
			transparent,
			var(--bright-red) 10%,
			transparent 50%,
			transparent
		);
	animation: 
		rotateBackground 3s linear infinite,
		rotateBackground2 8s linear infinite,
		rotateBackground3 13s linear infinite;
}

/* Change this background to transparent to see how the gradient works */
button div {
	background: var(--background); 
	padding: 1em 1.5em;
	border-radius: calc(var(--border-radius) - var(--border-size));
	color: var(--foreground);
}

@font-face {
	font-family: "Aspekta";
	font-weight: normal;
	src: url("https://assets.codepen.io/240751/Aspekta-300.woff2") format("woff2");
}