Dual Border Beam
Two beams leave the top in opposite directions, cross at the bottom and meet again at the top. Two conic arcs read one @property angle, the second one mirrored, so they always meet in the middle.
Also known as: two beams border animation, opposite direction border animation, crossing border light.
Dual beam
HTML
<div class="bdr-dual-border-beam">Dual beam</div>
CSS
@property --bdr-dual-border-beam-a {
syntax: "<angle>";
inherits: false;
initial-value: 0deg;
}
.bdr-dual-border-beam {
--c: var(--bdr-color, #3b82f6);
font-size: var(--bdr-size, 16px);
position: relative;
display: grid;
place-items: center;
width: 15em;
height: 8.5em;
border-radius: 1em;
font-family: system-ui, sans-serif;
font-weight: 600;
background: color-mix(in srgb, var(--c) 7%, transparent);
box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--c) 22%, transparent);
}
.bdr-dual-border-beam::before {
content: "";
position: absolute;
inset: 0;
padding: 0.15em;
border-radius: inherit;
background:
conic-gradient(from var(--bdr-dual-border-beam-a), transparent 0 78%, var(--c) 99.5%, transparent 0),
conic-gradient(from calc(var(--bdr-dual-border-beam-a) * -1), transparent 0 0.5%, color-mix(in oklch, var(--c), #ec4899 85%) 0, transparent 21.5%);
-webkit-mask: linear-gradient(#000 0 0) content-box, linear-gradient(#000 0 0);
-webkit-mask-composite: xor;
mask: linear-gradient(#000 0 0) content-box exclude, linear-gradient(#000 0 0);
pointer-events: none;
animation: bdr-dual-border-beam-cross 4s cubic-bezier(0.65, 0, 0.35, 1) infinite;
}
@keyframes bdr-dual-border-beam-cross {
0% { --bdr-dual-border-beam-a: 0deg; }
50% { --bdr-dual-border-beam-a: 180deg; }
100% { --bdr-dual-border-beam-a: 360deg; }
}
@media (prefers-reduced-motion: reduce) {
.bdr-dual-border-beam, .bdr-dual-border-beam *, .bdr-dual-border-beam::before, .bdr-dual-border-beam::after, .bdr-dual-border-beam *::before, .bdr-dual-border-beam *::after {
animation-duration: 0.01ms !important;
animation-iteration-count: 1 !important;
transition-duration: 0.01ms !important;
}
}Customizing this snippet
- Color: set
--bdr-coloron the element or a parent. Currently previewing#3b82f6. - Base size: set
--bdr-size. Every other dimension is inem, so the whole thing scales together. Currently previewing16px. - Speed: change the duration on the
transitionoranimationshorthand. Staggered delays are relative, so they keep their rhythm. - Reduced motion: the rule at the end of the CSS turns the motion off for people who asked their OS for less of it. Keep it.