Top Highlight Border
A bright gradient line glides back and forth along the top edge of a dark card and casts a soft light below it, the detail on many developer sites. Both layers move with transform only.
Also known as: gradient top border css, card top border light, top edge glow card css.
Changelog
Builds are twice as fast.
HTML
<div class="bdr-top-highlight-border"> <strong class="bdr-top-highlight-border-title">Changelog</strong> <span class="bdr-top-highlight-border-text">Builds are twice as fast.</span> </div>
CSS
.bdr-top-highlight-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;
align-content: center;
gap: 0.3em;
overflow: hidden;
background: color-mix(in srgb, var(--c) 10%, #0b0f19);
box-shadow: inset 0 0 0 1px color-mix(in srgb, #fff 10%, transparent);
color: #f1f5f9;
}
.bdr-top-highlight-border::before,
.bdr-top-highlight-border::after {
content: "";
position: absolute;
top: 0;
left: 0;
width: 6em;
pointer-events: none;
animation: bdr-top-highlight-border-glide 4s cubic-bezier(0.45, 0, 0.55, 1) infinite alternate;
}
.bdr-top-highlight-border::before {
z-index: 1;
height: 0.12em;
background: linear-gradient(90deg, transparent, color-mix(in srgb, var(--c) 30%, #fff) 50%, transparent);
}
.bdr-top-highlight-border::after {
height: 3.5em;
background: radial-gradient(50% 100% at 50% 0, color-mix(in srgb, var(--c) 40%, transparent), transparent);
}
.bdr-top-highlight-border-title { font-size: 1.05em; }
.bdr-top-highlight-border-text {
color: color-mix(in srgb, #fff 60%, transparent);
font-size: 0.8em;
font-weight: 400;
}
@keyframes bdr-top-highlight-border-glide {
from { transform: translateX(0.5em); }
to { transform: translateX(8.5em); }
}
@media (prefers-reduced-motion: reduce) {
.bdr-top-highlight-border, .bdr-top-highlight-border *, .bdr-top-highlight-border::before, .bdr-top-highlight-border::after, .bdr-top-highlight-border *::before, .bdr-top-highlight-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.