Corner Brackets Fill Button
Four corner brackets frame the label like a viewfinder; on hover they thicken and reach inward until they tile a solid fill. Eight gradient layers and one background-size transition.
Also known as: four corners fill hover, viewfinder button, corner border button.
HTML
<button class="hfx-corner-brackets-fill">Take a tour</button>
CSS
.hfx-corner-brackets-fill {
--c: var(--hfx-color, #3b82f6);
position: relative;
isolation: isolate;
overflow: hidden;
display: inline-flex;
align-items: center;
justify-content: center;
gap: 0.5em;
padding: 0.75em 1.75em;
border-radius: 0.3em;
font: 600 var(--hfx-size, 16px)/1.2 system-ui, sans-serif;
white-space: nowrap;
cursor: pointer;
border: 0;
background: transparent;
color: var(--c);
transition: color 0.25s ease 0.12s;
}
.hfx-corner-brackets-fill::before {
--arm: 0.9em;
--t: 0.16em;
content: "";
position: absolute;
inset: 0;
z-index: -1;
background:
linear-gradient(var(--c) 0 0) 0 0,
linear-gradient(var(--c) 0 0) 0 0,
linear-gradient(var(--c) 0 0) 100% 0,
linear-gradient(var(--c) 0 0) 100% 0,
linear-gradient(var(--c) 0 0) 0 100%,
linear-gradient(var(--c) 0 0) 0 100%,
linear-gradient(var(--c) 0 0) 100% 100%,
linear-gradient(var(--c) 0 0) 100% 100%;
background-repeat: no-repeat;
background-size:
var(--arm) var(--t), var(--t) var(--arm),
var(--arm) var(--t), var(--t) var(--arm),
var(--arm) var(--t), var(--t) var(--arm),
var(--arm) var(--t), var(--t) var(--arm);
transition: background-size 0.4s cubic-bezier(0.65, 0, 0.35, 1);
}
.hfx-corner-brackets-fill:is(:hover, :focus-visible) { color: #fff; }
.hfx-corner-brackets-fill:is(:hover, :focus-visible)::before {
background-size: 51% 51%;
}
@media (prefers-reduced-motion: reduce) {
.hfx-corner-brackets-fill, .hfx-corner-brackets-fill *, .hfx-corner-brackets-fill::before, .hfx-corner-brackets-fill::after, .hfx-corner-brackets-fill *::before, .hfx-corner-brackets-fill *::after {
animation-duration: 0.01ms !important;
animation-iteration-count: 1 !important;
transition-duration: 0.01ms !important;
}
}Customizing this snippet
- Color: set
--hfx-coloron the element or a parent. Currently previewing#3b82f6. - Base size: set
--hfx-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.