`blinds`

Parallel louvres wipe across themselves at once.

The full recording — the example app on an Android emulator and an iOS simulator at once, with blinds played several times over. Scrub or pause with the controls.

The screen is cut into bands parallel slabs and each one wipes across itself, all at the same time. A higher count reads as finer louvres.

Options it takes

Option	Type	Default	What it does here
`direction`	`'top' \| 'bottom' \| 'left' \| 'right'`	`'bottom'`	Both edges are used, so this picks the axis rather than an edge: `top`/`bottom` work horizontally, `left`/`right` vertically. `'top'` sweeps upward — horizontal edge `'bottom'` sweeps downward — horizontal edge (default) `'left'` sweeps left — vertical edge `'right'` sweeps right — vertical edge
`angleDeg`	`number`	`0`	Tilt of the boundary line. The sweep still travels along `direction`; the line doing the sweeping is raked over. Positive is clockwise on screen. Any value is accepted and wrapped.
`bands`	`number`	`6`	How many parallel slabs the screen is cut into. Clamped natively to 2…24.
`durationMs`	`number`	`650`	Animation length. Clamped up to this kind’s floor; `0` means no animation and is never clamped.
`settleFrames`	`number`	`2`	Display frames to hold the snapshot before revealing, so the theme swap has painted underneath.

Ignored by this kind: origin, shape, blurStyle. Passing them is harmless.

Minimum duration

A request below 300ms is clamped up to it, natively, so both platforms agree. Below that floor a full-screen copy coming apart has too few frames to read as motion — the eye gets the start and the end and nothing in between, which looks like a flicker rather than a fast transition. durationMs: 0 still means “no animation” and is never clamped.

Usage

withThemeTransition(applyTheme, {
  kind: 'blinds',
  durationMs: 650,
  direction: 'bottom',
  angleDeg: 0,
  bands: 6,
});

How it is done

iOS	N animated slabs in one mask path
Android	`Canvas.clipPath` over all of them