Sun to Moon Icon Hover: CSS Hover Effect

Sun to Moon Icon Hover

A theme toggle where the sun spins away and shrinks as the moon spins in, and the button dims to night. Two icons share one grid cell and trade places with a springy rotate and scale.

Also known as: dark mode toggle icon animation, theme toggle hover css, day night icon switch.

Color Base size 16px Dark background Hold hover state

HTML

<button class="hfx-sun-moon-swap" aria-label="Switch to dark mode">
  <svg class="hfx-sun-moon-swap-sun" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><circle cx="12" cy="12" r="4"/><path d="M12 2v2M12 20v2M4.9 4.9l1.4 1.4M17.7 17.7l1.4 1.4M2 12h2M20 12h2M4.9 19.1l1.4-1.4M17.7 6.3l1.4-1.4"/></svg>
  <svg class="hfx-sun-moon-swap-moon" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2" stroke-linecap="round" stroke-linejoin="round" aria-hidden="true"><path d="M20.5 14.1A8.5 8.5 0 1 1 9.9 3.5a6.6 6.6 0 0 0 10.6 10.6Z"/></svg>
</button>

CSS

.hfx-sun-moon-swap {
  --c: var(--hfx-color, #3b82f6);
  font-size: var(--hfx-size, 16px);
  position: relative;
  display: grid;
  place-items: center;
  width: 3.5em;
  height: 3.5em;
  padding: 0;
  border: 0;
  border-radius: 50%;
  cursor: pointer;
  background: color-mix(in srgb, var(--c) 12%, transparent);
  color: var(--c);
  transition: background-color 0.4s ease, color 0.4s ease;}
.hfx-sun-moon-swap svg {
  grid-area: 1 / 1;
  width: 1.6em;
  height: 1.6em;
  transition: transform 0.55s cubic-bezier(0.34, 1.56, 0.64, 1), opacity 0.25s ease;
}
.hfx-sun-moon-swap-moon {
  opacity: 0;
  transform: rotate(-90deg) scale(0.3);
}
.hfx-sun-moon-swap:is(:hover, :focus-visible) {
  background: color-mix(in srgb, var(--c) 30%, #0b1120);
  color: #fff;
}
.hfx-sun-moon-swap:is(:hover, :focus-visible) .hfx-sun-moon-swap-sun {
  opacity: 0;
  transform: rotate(90deg) scale(0.3);
}
.hfx-sun-moon-swap:is(:hover, :focus-visible) .hfx-sun-moon-swap-moon {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

@media (prefers-reduced-motion: reduce) {
  .hfx-sun-moon-swap, .hfx-sun-moon-swap *, .hfx-sun-moon-swap::before, .hfx-sun-moon-swap::after, .hfx-sun-moon-swap *::before, .hfx-sun-moon-swap *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
}

Customizing this snippet

Color: set --hfx-color on the element or a parent. Currently previewing #3b82f6.
Base size: set --hfx-size. Every other dimension is in em, so the whole thing scales together. Currently previewing 16px.
Speed: change the duration on the transition or animation shorthand. 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.

Sun to Moon Icon Hover

HTML

CSS

Customizing this snippet

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