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The idea
setAnticipation slows a reel so the player has time to feel the tension. On its own, the slow reel shows whatever random symbols happen to be wrapping onto the strip. sometimes the high-value lands, sometimes it doesn’t.
Pairing it with a buffer-above prefill (bufferAbove: ['COIN'] on the column’s ColumnTarget) turns the wait into a reveal: the COIN is the next cell to enter the visible area, so as the reel decelerates the player watches it slide into place. The effect is stronger than anticipation alone.
The minimum code
const promise = reelSet.spin();
await waitForServer();
const visible = await server.spin();
// Reels 3 and 4 are the slow reels. bufferAbove on those reels holds
// the symbol that slides into view as each reel decelerates.
const result: ColumnTarget[] = visible.map((col, i) => (
i === 3 || i === 4 ? { visible: col, bufferAbove: ['BONUS'] } : { visible: col }
));
reelSet.setAnticipation([3, 4]);
reelSet.setResult(result);
await promise;
When to use which symbol
- Same as the win: if reels 3+4 ARE landing on BONUS, prefill BONUS. The reveal is the win itself.
- The “tease” variant: if reels 3+4 are NOT landing on BONUS, prefill BONUS anyway. the slow reel briefly shows the bonus passing overhead before it scrolls out and the actual (non-bonus) symbol lands. This is a near-miss effect. Caveat: some slot jurisdictions restrict deliberately engineered near-misses. Confirm with your compliance team before shipping this variant.
How the reveal works
spin()starts → all reels acceleratesetResult+setAnticipationarrives → reels 0–2 enterStopPhasefirst- Reels 3 and 4 enter
AnticipationPhase. they slow down, holding foranticipationDelay - During that hold, the strip wraps slowly. The buffer-above cell (containing
BONUS) is the next to enter view - After
anticipationDelayelapses, those reels enterStopPhaseand land
The buffer-above prefill is read by the same FrameBuilder pipeline that landed the result. Pins, big symbols, and held reels all coexist with it.
Where to go next
- Peek symbol from buffer-above. the base mechanic on its own
- Buffer indexing cheatsheet. full convention reference
- Anticipate a reel. anticipation without the buffer-above pairing