How the Split-Flap Flip Animation Works
AnyTool Flip Clock renders each digit as a split-flap card — a hinged card split horizontally into a top half and a bottom half — and animates a flip purely with CSS 3D transforms, with no animation library and no images. When a digit changes, the card shows the new digit statically on its top half and the old digit on its bottom half, then overlays two animated leaves: a top leaf carrying the old digit rotates down from 0° to −90° about its bottom edge, and immediately after, a bottom leaf carrying the new digit rotates up from 90° to 0° about its top edge. Using transform-style: preserve-3d and backface-visibility: hidden, the two-stage rotation reproduces the mechanical train-station board effect in roughly 0.6 seconds. The clock itself is a row of these cards grouped into hour, minute and (optional) second fields, re-evaluated several times a second so each card flips exactly when its digit advances; a prefers-reduced-motion media query collapses the animation for users who request reduced motion.
- Each digit is a split-flap card with a top and bottom half divided by a hinge line
- A top leaf rotates 0°→−90° (old digit) then a bottom leaf rotates 90°→0° (new digit)
- Pure CSS: transform-style preserve-3d + backface-visibility hidden, no library, no images
- Cards are grouped into hour / minute / optional second fields and flip per digit change
- A prefers-reduced-motion query disables the flip for accessibility
