Spotlight Border
A lamp at the bottom of the box swings a cone of light from side to side, lighting the border wherever it lands. The conic angle eases between two limits instead of turning all the way round.
Also known as: conic spotlight border, sweeping light border, searchlight border css.
Spotlight
HTML
<div class="bdr-spotlight-border">Spotlight</div>
CSS
@property --bdr-spotlight-border-a {
syntax: "<angle>";
inherits: false;
initial-value: 0deg;
}
.bdr-spotlight-border {
--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;
--beam: conic-gradient(from var(--bdr-spotlight-border-a) at 50% 100%, transparent, color-mix(in srgb, var(--c) 70%, #fff) 18deg, transparent 36deg);
isolation: isolate;
overflow: hidden;
background:
radial-gradient(1.4em 0.5em at 50% 100%, color-mix(in srgb, var(--c) 50%, #fff), transparent),
color-mix(in srgb, var(--c) 10%, #0b0f19);
color: #f1f5f9;
animation: bdr-spotlight-border-sweep 3.2s cubic-bezier(0.45, 0, 0.55, 1) infinite;
}
.bdr-spotlight-border::before,
.bdr-spotlight-border::after {
content: "";
position: absolute;
inset: 0;
border-radius: inherit;
pointer-events: none;
}
.bdr-spotlight-border::before {
z-index: -1;
background: var(--beam);
opacity: 0.2;
}
.bdr-spotlight-border::after {
padding: 0.14em;
background: var(--beam), color-mix(in srgb, var(--c) 14%, transparent);
-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);
}
@keyframes bdr-spotlight-border-sweep {
0%, 100% { --bdr-spotlight-border-a: -62deg; }
50% { --bdr-spotlight-border-a: 26deg; }
}
@media (prefers-reduced-motion: reduce) {
.bdr-spotlight-border, .bdr-spotlight-border *, .bdr-spotlight-border::before, .bdr-spotlight-border::after, .bdr-spotlight-border *::before, .bdr-spotlight-border *::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.