---
title: "Falling-piece puzzles: API"
package: "@phaser-ae/faller"
tier: Pro
version: 3.0.0-4
released: 2026-10-14
updated: 2026-10-20
description: "Frame-timed rules for falling-piece games, from line-clearing blocks to colour-matching jewels, capsules and chains, with classic presets and every rule configurable."
url: https://phaser.io/packs/faller/api
site: Phaser - https://phaser.io
---

# Falling-piece puzzles: API

`@phaser-ae/faller` — Frame-timed, fully configurable rules for falling-piece games, with presets modelled on Tetris (Guideline and NES), Columns, Dr. Mario and Puyo Puyo.

## The pack

### `faller`

```ts
function faller(): Pack<{ faller: FallerApi }>
```

The `faller` pack. Pure logic, so it needs no backend and runs headless.

## Helpers

### `capsuleRotation`

```ts
function capsuleRotation(): RotationSystem
```

Dr. Mario capsules: two halves in a 2x2 box whose bottom-left cell is always filled. States: 0 = horizontal
[a b], 1 = vertical a over b, 2 = horizontal [b a], 3 = vertical b over a (clockwise order). A turn to horizontal
that is blocked on the right kicks one column left (NES); a turn to vertical has no kick. Halves carry links so
they stay joined after locking until one of them is cleared. Spawn: horizontal, left half at column
floor(cols / 2) - 1 (columns 4-5 of 8), row 0.

### `COLUMNS_GRAVITY_FRAMES`

```ts
const COLUMNS_GRAVITY_FRAMES: readonly [40, 34, 29, 25, 21, 18, 15, 13, 11, 9, 8, 7, 6, 5, 4, 3, 2]
```

Columns frames per row by level (est.: no published table was found; tuned to the arcade's pace).

### `COLUMNS_JEWELS_PER_LEVEL`

```ts
const COLUMNS_JEWELS_PER_LEVEL: { readonly easiest: 50; readonly easy: 40; readonly normal: 35; readonly hard: 25; }
```

Jewels per level by the arcade's difficulty DIP switch (Sega "Columns Conversion" manual, Figure 9).

### `COLUMNS_START`

```ts
const COLUMNS_START: { readonly 0: 0; readonly 5: 20000; readonly 10: 50000; }
```

The arcade's start choices (KLOV screenshot of the level select): level and starting bonus.

### `columnsArcade`

```ts
function columnsArcade(opts: ColumnsOptions = {}): FallerRules
```

Columns (Sega 1990): three-jewel columns that fall in half-row steps and cycle their order with the button;
matches of three or more in rows, columns and diagonals; cascades scored 30 x step x lines-of-three x (level + 1);
a level every 35 jewels (DIP); the start-level bonus; the magic jewel that clears every jewel of the colour it lands
on; game over when jewels are left above the well.

### `columnsScoring`

```ts
function columnsScoring(): ScoringFn
```

Columns scoring, after the Mega Drive analysis on TASVideos (forum topic 5090): each chain step scores
30 x step x lines-of-three x (level + 1), where a run of four is two lines of three and five is three. Soft drop
scores (level + 1) per half row, i.e. 2 x (level + 1) per row. A magic-jewel clear has no documented value; this
scores 10 x (level + 1) per jewel, the per-jewel rate of a line of three (an estimate, noted in the docs).

### `CRASH`

```ts
const CRASH: 100
```

Colour offset that marks a crash gem: a crash gem of colour c is stored as CRASH + c.

### `CRASH_DAMAGE`

```ts
const CRASH_DAMAGE: CrashDamage
```

Damage as estimated by players of the original (no published formula exists): a broken gem is worth one counter gem,
a power gem cell 1.25 (a 2 x 2 power gem and its crash gem send about six), each gem in chain step n counts n
times, a destroyed counter gem 0.5, and the diamond's break is halved (HD Remix: 80 %).

### `crashGemDeal`

```ts
function crashGemDeal(r: CrashGemRules): PieceSpec[]
```

Builds the pre-generated drop order: both boards on one seed get the same pairs (as in the original).

### `crashGemFallerRules`

```ts
function crashGemFallerRules(r: CrashGemRules): FallerRules
```

The FallerRules a crash-gem board runs its pair with (matching off; this module resolves moves).

### `createCrashGems`

```ts
function createCrashGems(rules: CrashGemRules): CrashGemGame
```

Creates a crash-gem board. Throws a RangeError for an unsupported configuration.

### `createFaller`

```ts
function createFaller(rules: FallerRules): FallerGame
```

Creates a game from a ruleset.

### `cycleRotation`

```ts
function cycleRotation(length = 3, spawnColumn?: (cols: number) => number): RotationSystem
```

Columns: a vertical column of `length` jewels (origin = the bottom jewel). Rotating does not move the
footprint; it cycles the colours (clockwise moves every jewel down one place and the bottom one to the top).
A magic column does not cycle.

### `deal`

```ts
function deal(rule: DealRule, memory: DealMemory, rng: Rng): PieceSpec
```

Deals the next piece by `rule`, updating `memory`.

### `dealMemory`

```ts
function dealMemory(): DealMemory
```

A fresh dealer memory.

### `DIAGONAL_SEND_RATE`

```ts
const DIAGONAL_SEND_RATE = (raw: number): number=> …
```

The original's send rate for the two diagonal patterns: floor(x / 4) + floor(x / 2), about 75 %.

### `DIAMOND`

```ts
const DIAMOND: 200
```

Colour code of the diamond.

### `DR_MARIO_BASE`

```ts
const DR_MARIO_BASE: readonly [100, 200, 300]
```

Dr. Mario base points per virus by speed: LOW, MED, HI.

### `DR_MARIO_GRAVITY_FRAMES`

```ts
const DR_MARIO_GRAVITY_FRAMES: readonly [70, 68, 66, 64, 62, 60, 58, 56, 54, 52, 50, 48, 46, 44, 42, 40, 38, 36, 34, 32, 30, 28, 26, 24, 22, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 10, 9, 9, 8, 8, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 5, 5, 5, 5, 5, 4, 4, 4, 4, 4, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1]
```

Dr. Mario NES NTSC frames per row by speed index 0..80 (https://tetris.wiki/Dr._Mario).

### `DR_MARIO_MULTIPLIERS`

```ts
const DR_MARIO_MULTIPLIERS: readonly [1, 2, 4, 8, 16, 32]
```

Dr. Mario per-virus multipliers for the 1st..6th+ virus of one move (https://www.mariowiki.com/Dr._Mario_(game)).

### `DR_MARIO_SPEED_START`

```ts
const DR_MARIO_SPEED_START: readonly [15, 25, 31]
```

Starting speed index for LOW, MED and HI.

### `drMario`

```ts
function drMario(opts: DrMarioOptions = {}): FallerRules
```

Dr. Mario (Nintendo 1990): 8 x 16 bottle, viruses placed by the NES algorithm (count 4 x (level + 1), max 84;
rows by level; the distance-two colour rule), capsules from a 128-entry loop of the nine colour pairs, the 2x2
rotation with the left kick, four in a row or column clears (viruses included), unsupported halves fall at four
rows a second, LOW/MED/HI speeds with a speed-up every ten capsules, scoring by viruses per move, level clear and
top-out when the bottle's neck is blocked.

### `drMarioScoring`

```ts
function drMarioScoring(): ScoringFn
```

Dr. Mario scoring: only viruses score. The k-th virus cleared in one move (a capsule and every cascade it
causes) is worth base x 1, 2, 4, 8, 16, 32 (sixth and later), with base 100 / 200 / 300 for LOW / MED / HI.

### `DROP_PATTERNS`

```ts
const DROP_PATTERNS: Readonly<Record<string, DropPattern>>
```

The eleven drop patterns of Super Puzzle Fighter II Turbo (1996), read from the original-pattern charts in David
Sirlin's "Balancing Puzzle Fighter" (2014; he rebalanced the game for HD Remix and published the old patterns),
cross-checked against the row layout in the X' rebalance patch source (github.com/KScl/puzzle-fighter-x-prime).
Keys are neutral descriptions; `source` names the fighter that used the pattern.

### `GEM_LETTERS`

```ts
const GEM_LETTERS: Readonly<Record<string, number>>
```

Colour letters used by drop patterns: R G B Y = 0 1 2 3 (the original's red, green, blue, yellow).

### `gemColor`

```ts
function gemColor(c: Cell): number
```

The base colour of a cell (crash gems and counter gems included); -1 for the diamond.

### `gemPairRotation`

```ts
function gemPairRotation(spawnColumn: (cols: number) => number): RotationSystem
```

The pair rotation of a crash-gem board: Puyo-style orbit with wall and floor kicks, except that a vertical pair
wedged in a one-wide well flips 180 degrees on a single press (the original; Sirlin 2014, "the diamond trick").

### `gemType`

```ts
function gemType(c: Cell): GemType
```

The gem type of a cell.

### `guidelineAttack`

```ts
function guidelineAttack(e: LinesEvent): number
```

Lines of garbage sent by a Guideline line clear (the common Guideline attack table): single 0, double 1,
triple 2, tetris 4; T-spin single 2, double 4, triple 6 (mini: 0 / 1); +1 back-to-back; combo bonus by count
0,1,1,2,2,3,3,4,4,4,5. A versus layer can supply its own table; the faller pack only reports it.

### `guidelineGravity`

```ts
function guidelineGravity(level: number): number
```

Guideline Marathon gravity (https://tetris.wiki/Marathon): (0.8 - (level - 1) x 0.007)^(level - 1) seconds per
row, as rows per 60 Hz frame; 20G (instant) from level 20.

### `guidelineScoring`

```ts
function guidelineScoring(opts: GuidelineScoringOptions = {}): ScoringFn
```

Tetris Guideline scoring (https://tetris.wiki/Scoring): single 100, double 300, triple 500, tetris 800;
T-spin mini 100 (no lines) / 200 (single) / 400 (double); T-spin 400 / 800 / 1200 / 1600; all times the level
BEFORE the clear. Difficult clears in a row earn x1.5 (back-to-back); combos add 50 x combo x level; soft drop
1 per row, hard drop 2 per row (never multiplied).

### `NES_GRAVITY_FRAMES`

```ts
const NES_GRAVITY_FRAMES: readonly [48, 43, 38, 33, 28, 23, 18, 13, 8, 6, 5, 5, 5, 4, 4, 4, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1]
```

NES Tetris NTSC frames per row by level 0..29 (https://tetris.wiki/Tetris_(NES,_Nintendo)).

### `nesAre`

```ts
function nesAre(ctx: TimingContext): number
```

NES entry delay: 10 frames for a lock in the bottom two rows, 2 more for each 4 rows above, up to 18.

### `nesScoring`

```ts
function nesScoring(): ScoringFn
```

NES Tetris scoring (https://tetris.wiki/Scoring, meatfighter's ROM analysis): 40 / 100 / 300 / 1200 x (level + 1),
using the level AFTER the clear is counted, plus push-down points (rows of the final soft drop, not multiplied).

### `NRS_SHAPES`

```ts
const NRS_SHAPES: Record<string, XY[][]>
```

NES (Nintendo Rotation System) orientations, relative to the pivot, from the orientation table in
meatfighter's analysis of the ROM. Each list is in CLOCKWISE order; `NRS_SPAWN` gives the spawn index.

### `NRS_SPAWN`

```ts
const NRS_SPAWN: Record<string, number>
```

NES spawn orientations (Td, Jd, Zh, O, Sh, Ld, Ih) as indices into `NRS_SHAPES`.

### `nrsRotation`

```ts
function nrsRotation(): RotationSystem
```

The Nintendo Rotation System of NES Tetris: pivot rotation, right-handed, no kicks, spawn at column 5, row 0.

### `nuisanceFromScore`

```ts
function nuisanceFromScore(score: number, targetPoints = 70, carry = 0): { nuisance: number; carry: number }
```

Puyo nuisance from a chain score (https://puyonexus.com/wiki/Scoring): NP = score / targetPoints + carry; the
whole part is sent, the fraction carries to the next chain. Target points are 70 in Tsu.

### `pairRotation`

```ts
function pairRotation(spawnColumn?: (cols: number) => number): RotationSystem
```

Puyo pairs: the axis puyo stays put and the child orbits it. A turn into a wall or another puyo pushes the pair
one cell away; a turn into the floor lifts it one row. A vertical pair wedged between walls cannot turn; a
second press then flips it 180 degrees (the quick turn), lifting it if the child would go into the floor.
Colours are [axis, child]. `spawnColumn` defaults to the third column of six (floor((cols - 1) / 2)).

### `placeViruses`

```ts
function placeViruses(field: Field, rng: Rng, level: number, rule: VirusRule): number
```

Places Dr. Mario viruses by the NES algorithm (https://tetris.wiki/Dr._Mario): pick a row up to the level's
maximum and a column; colour = remaining % 4 (0 yellow, 1 red, 2 blue; 3 = random from the 16-entry table);
step right (wrapping up a row) past occupied cells and past cells whose distance-two neighbours already hold all
three colours; change the colour (yellow -> blue, red -> yellow, blue -> red) until no distance-two neighbour
shares it. Rows count from 1 at the bottom. Returns the number placed.

### `PUYO_COLOR_BONUS`

```ts
const PUYO_COLOR_BONUS: readonly [0, 3, 6, 12, 24, 48]
```

Puyo colour bonus by colours cleared in one step (1..6), Tsu (https://puyonexus.com/wiki/Scoring).

### `PUYO_GRAVITY_FRAMES`

```ts
const PUYO_GRAVITY_FRAMES: readonly [36, 30, 26, 22, 19, 16, 14, 12, 10, 8, 7, 6, 5, 4, 3, 2]
```

Puyo frames per row by level (est.: endless is not a Tsu mode; this is a gentle curve from Tsu's opening pace).

### `PUYO_GROUP_BONUS`

```ts
const PUYO_GROUP_BONUS: readonly [0, 2, 3, 4, 5, 6, 7, 10]
```

Puyo group bonus by group size 4..11+ (https://puyonexus.com/wiki/Scoring).

### `PUYO_LETTERS`

```ts
const PUYO_LETTERS: Record<string, number>
```

Letter-to-colour map for Puyo layouts: R, G, B, Y, P.

### `PUYO_MISSIONS`

```ts
const PUYO_MISSIONS: readonly PuyoMission[]
```

Authored missions (original puzzles in the nazo-puyo style; solvable, verified by the tests).

### `PUYO_TSU_CHAIN_POWER`

```ts
const PUYO_TSU_CHAIN_POWER: readonly [0, 8, 16, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 480, 512, 544, 576, 608, 640, 672]
```

Puyo Puyo Tsu chain power for chains 1..24 (https://puyonexus.com/wiki/Chain_Power_Table); 24+ stays at 672...

### `puyoStepScore`

```ts
function puyoStepScore(chain: number, groups: readonly number[], colors: number, popSize = 4): number
```

The Puyo Puyo Tsu score of one chain step: 10 x PC x clamp(CP + CB + GB, 1, 999). `popSize` is the minimum group (4).

### `puyoTsu`

```ts
function puyoTsu(opts: PuyoOptions = {}): FallerRules
```

Puyo Puyo Tsu single-player field rules: 6 x 12 with a hidden 13th row (it holds puyos but never pops) and a 14th
row where puyos vanish; pairs that orbit their axis with wall and floor kicks and the double-press quick turn;
groups of four or more pop, nuisance next to a pop clears, cascades score 10 x PC x (chain power + colour bonus +
group bonus) with Tsu's tables; all clears; the X in the third column ends the game. Nuisance (versus) follows
Tsu: 30 at most per move, whole rows first then random distinct columns, 70 target points, +30 after an all clear.
Modes: endless (speed rises every `piecesPerLevel` pieces: a house mode, Tsu has none) and missions.

### `puyoTsuScoring`

```ts
function puyoTsuScoring(popSize = 4): ScoringFn
```

Puyo Puyo Tsu scoring: chain steps by `puyoStepScore`; soft drop 1 per row.

### `puzzleFighter`

```ts
function puzzleFighter(opts: PuzzleFighterOptions = {}): CrashGemRules
```

Super Puzzle Fighter II Turbo (Capcom, 1996) board rules. From the PlayStation manual (Capcom): pairs of gems drop
from the top centre; a crash gem breaks the gems of its colour linked to it; four or more same-coloured gems in a
rectangle form a power gem; counter gems start at 5 and turn into normal gems at 0, counting down as each pair
falls; counter gems that still fall after some are countered start at 3; counter gems touching a break are
destroyed whatever their colour; the rainbow gem (diamond) breaks every gem of one colour for fewer counter gems;
the round is lost when gems pile into the gap where new gems fall. From Wikipedia and Sirlin (2014): a 6 x 12 board
whose fourth column takes the new pair; the diamond every 25 pairs; diamond damage 50 % (HD Remix 80 %); the 70 %
(ROM: floor(x/4) + floor(x/2)) send rate of the two diagonal patterns; one press flips a pair wedged in a one-wide
well. Estimates (no published figures): the damage values above, the crash gem rate (1 in 8 gems), the drop speed
table, the lock delay, flash and fall timings, the columns a partial counter row lands in (random), and the score
(10 a gem x chain step).

### `SRS_KICKS_I`

```ts
const SRS_KICKS_I: Record<string, readonly (readonly [number, number])[]>
```

SRS wall kicks for the I piece, same convention as `SRS_KICKS_JLSTZ`.

### `SRS_KICKS_JLSTZ`

```ts
const SRS_KICKS_JLSTZ: Record<string, readonly (readonly [number, number])[]>
```

SRS wall kicks for J, L, S, T and Z, keyed `from>to` (0, 1 = R, 2, 3 = L), in the wiki's convention
(+x right, +y UP). Five tests, tried in order.

### `SRS_SHAPES`

```ts
const SRS_SHAPES: Record<string, XY[][]>
```

SRS shapes, per kind, per rotation state (0 = spawn, R, 2, L), relative to the top-left of the bounding box.

### `srsRotation`

```ts
function srsRotation(): RotationSystem
```

The Super Rotation System (Tetris Guideline): SRS shapes, spawn centred (rounded left) in rows 21-22, and the
full five-test kick tables, I piece included. 180-degree rotation is not part of SRS: it is two 90-degree
turns' worth of state with only the plain test, and the engine offers it only when a ruleset enables it.

### `tableRotation`

```ts
function tableRotation(opts: TableRotationOptions): RotationSystem
```

Builds a rotation system from shape tables (and optional kick tables): SRS, NRS or your own pieces.

### `tetrisGuideline`

```ts
function tetrisGuideline(opts: GuidelineOptions = {}): FallerRules
```

Tetris by the Guideline: SRS with full kicks, 7-bag, hold, a next queue, ghost, 0.5 s lock delay with 15 move
resets (restored on reaching a new lowest row), soft drop at 20x gravity (1 point a row), hard drop (2 points a
row), T-spins (3-corner, mini by the pointing side, upgraded by the fifth kick), back-to-back x1.5, combos, the
Marathon gravity curve, 10 lines a level, block-out / lock-out top-out, and a 20-row buffer above the well.

### `tetrisNes`

```ts
function tetrisNes(opts: NesOptions = {}): FallerRules
```

NES Tetris (Nintendo 1989): the Nintendo Rotation System (right-handed, no kicks), no hold, no hard drop, no
ghost, the NES gravity table, DAS 16/6 (charge kept between pieces, frozen during ARE, charged by a wall,
shifting ignored while Down is held), soft drop at 1/2G after 3 frames that must be re-pressed for each piece,
no lock delay, ARE 10-18 by lock height plus 17-20 frames for a line clear, 40/100/300/1200 x (level + 1)
scoring plus push-down points, the NES level-up rule, the reroll randomiser, and a 999,999 score cap.

### `TETROMINOES`

```ts
const TETROMINOES: readonly ["I", "O", "T", "S", "Z", "J", "L"]
```

The seven tetromino kinds in Guideline colour order: I cyan, O yellow, T purple, S green, Z red, J blue, L orange.

## Classes

### `CrashGemGame`

```ts
class CrashGemGame
```

A crash-gem board (Super Puzzle Fighter II Turbo rules). Drive it with `frame(input)` at 60 Hz; read the cells,
power gems, counter timers and the falling pair; drain events. Versus hooks: `queueCounters`, `offsetCounters`,
`pendingCounters`, and the `crash` / `moveEnd` events' `attack`.

- `readonly rules: CrashGemRules` — The ruleset.
- `readonly faller: FallerGame` — The pair engine (its well is this board's well).
- `constructor(rules: CrashGemRules)` — Creates a board.
- `reset(): void` — Starts the board over with the same rules and seed.
- `get phase(): CrashGemPhase` — Resolution phase ('piece' while a pair is in play or about to be).
- `get phaseProgress(): number` — Progress through the current resolution phase, 0..1.
- `get piecePhase(): string` — The pair engine's phase ('ready', 'are', 'active', ...).
- `get frameCount(): number` — Frames since the board started.
- `get score(): number` — Score.
- `get chain(): number` — Current chain step (0 when none).
- `get bestChain(): number` — Best chain this round.
- `get pendingCounters(): number` — Counter gems waiting to fall here.
- `get pendingBatches(): readonly CounterBatch[]` — The batches waiting (count, pattern, short countdown).
- `get over(): boolean` — True once the round is lost.
- `get reason(): string` — Why it ended.
- `get busy(): boolean` — True while a move is resolving (breaks, falls, counter gems landing).
- `get active(): FallerGame['active']` — The falling pair (colours encode the gem type; see `gemType`), or null.
- `next(): PieceSpec[]` — The next pair(s).
- `cell(x: number, y: number): Cell | null` — The cell at (x, y) (row 0 = top visible row).
- `counterTimer(id: number): number | undefined` — The countdown of a counter gem (by cell id), or undefined.
- `powerOf(id: number): number | undefined` — The power gem a cell belongs to (by cell id), or undefined.
- `get flashing(): readonly XY[] | null` — Gems flashing before they break.
- `get falling(): ReadonlyMap<number, number> | null` — Cells falling: id -> rows still to fall at the start of this step (multiply by 1 - phaseProgress).
- `powerGems(): PowerGem[]` — Every power gem on the board.
- `drain(): CrashGemEvent[]` — Removes and returns the pending events.
- `queueCounters(count: number, pattern: DropPattern = this.rules.pattern): void` — Queues counter gems from an attacker with its drop pattern. They fall after this board's next move resolves.
- `offsetCounters(count: number): number` — Cancels up to `count` waiting counter gems (newest first); the survivors start at the shorter countdown. Returns how many were cancelled.
- `snapshot(): CrashGemSnapshot` — A deep copy of the whole board.
- `restore(snap: CrashGemSnapshot): void` — Restores a snapshot taken from a board with the same rules.
- `frame(input: FallerInput = {}): void` — Advances one 60 Hz frame.
- `placements(): { x: number; rot: number }[]` — Every distinct final drop of the falling pair (see FallerGame.placements).
- `place(x: number, rot: number): boolean` — Teleports the pair to a placement and drops it (bots and tests). The move resolves on later frames.
- `settleMove(maxFrames = 20000): void` — Runs frames with no input until the next pair is in play or the round ends (bounded).
- `preview(x: number, rot: number): CrashGemPreview` — What placing the pair at (x, rot) would do, without changing this board: counter gems sent, chain, gems broken, whether the round would end, and the resulting board.

### `FallerGame`

```ts
class FallerGame
```

A falling-piece game. Drive it with `frame(input)` at 60 Hz; read its state; drain its events.

- `readonly rules: FallerRules` — The ruleset (treat as read-only; build a new game to change it).
- `readonly field: Field` — The well.
- `constructor(rules: FallerRules)` — Creates a game. Throws a RangeError describing any unsupported configuration.
- `reset(): void` — Starts the game over with the same rules and seed.
- `get phase(): FallerPhase` — Current phase.
- `get phaseProgress(): number` — Progress through the current phase, 0..1.
- `get frameCount(): number` — Frames since the game started.
- `get score(): number` — Score.
- `get level(): number` — Level.
- `get lines(): number` — Lines cleared (rows games).
- `get cleared(): number` — Cells cleared (Columns jewels, Puyo puyos, Dr. Mario cells).
- `get pieces(): number` — Pieces locked.
- `get speedIndex(): number` — Speed index (Dr. Mario).
- `get viruses(): number` — Viruses left (Dr. Mario).
- `get chain(): number` — Current chain step during a cascade (0 when none).
- `get bestChain(): number` — Best chain this game.
- `get combo(): number` — Combo counter (-1 = none).
- `get backToBack(): boolean` — True when the next difficult clear earns back-to-back.
- `get held(): PieceSpec | null` — Held piece.
- `get holdUsed(): boolean` — Hold already used for this piece.
- `get pendingNuisance(): number` — Nuisance waiting to fall.
- `get stats(): Readonly<Record<string, number>>` — Pieces dealt by kind.
- `get over(): boolean` — True once the game has ended either way.
- `get reason(): string` — Why the game ended ('' while running).
- `get goalProgress(): number` — Best progress toward the objective (chain reached, lines, score).
- `get targetPoints(): number` — Target points used for nuisance (Puyo). Sets target points (a versus layer lowers them during margin time).
- `set targetPoints(v: number)` — Target points used for nuisance (Puyo). Sets target points (a versus layer lowers them during margin time).
- `next(): PieceSpec[]` — The upcoming pieces, `rules.previews` of them.
- `cell(x: number, y: number): Cell | null` — The cell at (x, y) (row 0 = top visible row).
- `get active(): ActiveView | null` — The falling piece, or null.
- `ghost(): XY[]` — Where the falling piece would land.
- `get clearing(): { cells: XY[]; rows: number[]; magic: boolean } | null` — Cells being cleared (flashing), with the rows for a rows game.
- `get falling(): ReadonlyMap<number, number> | null` — Cells currently falling in a cascade: id -> rows still to fall at the start of this step (multiply by 1 - phaseProgress for the draw offset).
- `drain(): FallerEvent[]` — Removes and returns the pending events.
- `snapshot(): FallerSnapshot` — A deep copy of the whole game state (events excluded). Restore with `restore`.
- `restore(snap: FallerSnapshot): void` — Restores a snapshot taken from a game with the same rules.
- `queueNuisance(count: number): void` — Queues nuisance to fall after the player's next move resolves (Puyo rules: at most `maxPerDrop` per move).
- `offsetNuisance(count: number): number` — Cancels up to `count` pending nuisance (offsetting). Returns how many were cancelled.
- `queueGarbage(rows: number, hole?: number): void` — Queues garbage rows (rows games) that rise after the next piece locks without clearing lines.
- `frame(input: FallerInput = {}): void` — Advances one 60 Hz frame.
- `advance(seconds: number, input: FallerInput = {}): void` — Advances `seconds` of game time at 60 Hz with the same held input (edges apply to the first frame).
- `placements(): { x: number; rot: number }[]` — Every final placement of the falling piece reachable by rotating at spawn height and dropping (a bot's move list). For cycling pieces, `rot` counts colour rotations.
- `place(x: number, rot: number): boolean` — Puts the falling piece at a placement and drops it there: a teleport for bots and tests (no scoring for the movement). Returns false when the placement does not fit. The move then resolves on later frames.
- `settleMove(maxFrames = 20000): void` — Runs frames with no input until the next piece is in play or the game ends (bounded).
- `preview(x: number, rot: number): PlacementPreview` — What placing the current piece at (x, rot) would do, without changing this game: points, chains, attack, lines and whether the game would end. The AI search surface for a versus opponent.

### `Field`

```ts
class Field
```

The well grid. Rows run from -hidden (top of the buffer) to rows - 1 (bottom); row 0 is the top visible row.

- `readonly cols: number` — Width in cells.
- `readonly rows: number` — Visible height in cells.
- `readonly hidden: number` — Buffer rows above the visible well.
- `cells: (Cell | null)[]` — Cells, row-major from the top of the buffer. Exposed for snapshots; use `get`/`set`.
- `nextId: number` — The next id to hand out.
- `constructor(cols: number, rows: number, hidden: number)` — Creates an empty well.
- `inside(x: number, y: number): boolean` — True when (x, y) is inside the well, buffer included.
- `get(x: number, y: number): Cell | null` — The cell at (x, y), or null when empty or outside.
- `set(x: number, y: number, cell: Cell | null): void` — Writes a cell (null clears). Ignored outside the well.
- `put(x: number, y: number, color: number, kind: CellKind = 'block', link?: Link): Cell` — Creates and places a new cell, returning it.
- `fits(cells: readonly XY[]): boolean` — True when every cell is inside the well and empty.
- `each(fn: (cell: Cell, x: number, y: number) => void): void` — Calls `fn` for every occupied cell.
- `count(kind?: CellKind): number` — Number of occupied cells, optionally of one kind.
- `top(): number` — The highest occupied row, or `rows` when the well is empty.
- `clear(): void` — Empties the well.
- `fullRows(): number[]` — Rows that are completely filled, top to bottom.
- `collapseRows(rows: readonly number[]): void` — Removes the given rows and drops everything above them (Tetris "naive" gravity).
- `lineMatches(n: number, diagonals: boolean, minY = -this.hidden): LineMatch` — Runs of `n` or more same-coloured cells horizontally and vertically (and diagonally when asked), from row `minY` down. Nuisance and garbage never match. Viruses match like blocks (Dr. Mario).
- `floodMatches(n: number, minY = -this.hidden): MatchGroup[]` — Orthogonally connected same-coloured groups of `n` or more blocks at or below row `minY` (Puyo).
- `adjacentNuisance(cells: readonly XY[], minY = -this.hidden): XY[]` — Nuisance cells orthogonally next to any of `cells`, at or below `minY` (they clear with a popping group).
- `remove(cells: readonly XY[]): Cell[]` — Removes cells. A capsule half whose partner is removed becomes a free half. Returns the removed cells.
- `gravityStep(mode: 'cells' | 'linked'): number[]` — One step of gravity: every unsupported unit falls one row. `cells` mode moves each cell on its own; `linked` mode keeps joined capsule halves together. Viruses never fall. Returns the ids that moved.
- `unsupported(mode: 'cells' | 'linked'): boolean` — True when some unit would fall in a `gravityStep`.
- `dropNuisance(count: number, rng: Rng, ceiling = -this.hidden): { id: number; x: number; y: number; rows: number }[]` — Drops `count` nuisance into the well by the Puyo rules: whole rows of `cols` first, the remainder into distinct columns chosen at random. Each nuisance stacks on its column; any that would land above row `ceiling` vanishes. Returns each placed cell with how far it fell from just above the buffer.
- `raiseGarbage(rows: number, hole: number): boolean` — Pushes the stack up by `rows` and fills the bottom with garbage rows holed at `hole`. Returns true if anything was pushed out of the top of the buffer (a top-out).

## Types

### `ActiveView`

```ts
interface ActiveView
```

The falling piece as the renderer sees it.

- `kind: string` — Piece kind.
- `rot: number` — Rotation state.
- `x: number` — Origin column.
- `y: number` — Origin row.
- `sub: number` — Sub-row progress towards the next row (0..1), for smooth drawing of half-row systems.
- `blocks: { x: number; y: number; color: number; link?: PieceBlock['link'] }[]` — Absolute blocks.
- `magic: boolean` — Magic column (Columns).
- `serial: number` — Unique per piece; changes when a new piece appears (snap sprites on change).
- `grounded: boolean` — True while resting on the stack.
- `lockProgress: number` — Lock-delay progress 0..1 (for a lock flash).

### `Cell`

```ts
interface Cell
```

A locked cell. `id` is stable for the cell's lifetime (it survives falls), so a renderer can key sprites by it.

- `id: number` — Stable identity for this cell while it exists.
- `color: number` — Colour index (-1 for colourless cells such as nuisance).
- `kind: CellKind` — What the cell is.
- `link?: Link` — The capsule half this one is still joined to.

### `CellKind`

```ts
type CellKind = 'block' | 'virus' | 'nuisance' | 'garbage'
```

What a locked cell is. Viruses never fall; nuisance never matches on its own; garbage is Tetris filler.

### `ChainEvent`

```ts
interface ChainEvent
```

One step of a cascade in a matching game (Columns, Dr. Mario, Puyo).

- `type: 'chain'` — Event kind.
- `chain: number` — Chain step, 1 for the first clear of a move.
- `cleared: number` — Coloured cells cleared in this step (nuisance excluded).
- `colors: number` — Distinct colours cleared in this step.
- `groups: number[]` — Size of each group that popped (flood matching) or each colour set (line matching).
- `linesOfN: number` — Lines-of-N counted in this step (line matching: a run of four is two lines of three).
- `viruses: number` — Viruses cleared in this step.
- `virusesBefore: number` — Viruses already cleared earlier in this move.
- `magic: boolean` — True when the step was a Columns magic-jewel clear.
- `level: number` — Current level.
- `speed: number` — Speed setting (Dr. Mario: 0 low, 1 med, 2 hi).

### `ColumnsOptions`

```ts
interface ColumnsOptions
```

Options for `columnsArcade`.

- `difficulty?: FallerDifficulty` — Difficulty. Arcade: DIP Normal (35 jewels a level), full speed table. Normal: DIP Easy (40), speed capped at level 9. Easy: DIP Easiest (50), capped at level 5.
- `seed?: number` — Seed.
- `startLevel?: number` — Start level: 0, 5 (+20,000) or 10 (+50,000) as the arcade offers; any other level starts with no bonus.
- `jewelsPerLevel?: number` — Jewels per level (overrides the difficulty's DIP setting).
- `colors?: number` — Jewel colours. Default 6.
- `length?: number` — Column length. Default 3.
- `match?: number` — Match length. Default 3.
- `diagonals?: boolean` — Diagonal matches. Default true.
- `magic?: boolean` — Magic jewel. Default true.
- `cols?: number` — Well width. Default 6.
- `rows?: number` — Visible well height. Default 13.

### `CounterBatch`

```ts
interface CounterBatch
```

Counter gems waiting to fall on this board, with the pattern of the board that sent them.

- `count: number` — How many.
- `rows: string[]` — Pattern rows (top to bottom).
- `short: boolean` — Some were offset: these start at the shorter countdown.

### `CrashDamage`

```ts
interface CrashDamage
```

How breaks turn into counter gems. Every value is a counter-gem value before the send rate.

- `normal: number` — Per normal gem broken.
- `crash: number` — Per crash gem broken.
- `powerCell: number` — Per cell of a power gem broken.
- `counter: number` — Per counter gem destroyed next to a break.
- `chain: (step: number) => number` — Multiplier for chain step n (1 = the first break).
- `diamond: number` — Multiplier on the diamond's own break (the chain it sets off is not reduced).

### `CrashGemEvent`

```ts
type CrashGemEvent = | { type: 'ready' } | { type: 'spawn'; serial: number } | { type: 'move'; dx: number } | { type: 'rotate'; dir: number } | { type: 'land' } | { type: 'lock'; cells: XY[] } | { type: 'power'; gem: PowerGem } | { type: 'crash'; chain: number; cells: XY[]; gems: number; power: number; counters: number; diamond: boolean; attack: number; points: number } | { type: 'diamond'; color: number; cleared: number } | { type: 'tech' } | { type: 'counterTurn'; cells: XY[] } | { type: 'counters'; count: number } | { type: 'moveEnd'; chains: number; attack: number; gems: number } | { type: 'gameOver'; reason: string }
```

Events reported by `CrashGemGame.drain()`.

### `CrashGemPhase`

```ts
type CrashGemPhase = 'piece' | 'fall' | 'flash' | 'counter' | 'gameOver'
```

Resolution sub-phase.

### `CrashGemPreview`

```ts
interface CrashGemPreview
```

What a placement would do, from `CrashGemGame.preview`.

- `ok: boolean` — The placement fits.
- `attack: number` — Counter gems it would send.
- `chains: number` — Longest chain.
- `gems: number` — Gems it would break.
- `over: boolean` — It would end the round.
- `field: (Cell | null)[]` — The resulting board (row-major from the top of the buffer).

### `CrashGemRules`

```ts
interface CrashGemRules
```

A complete crash-gem ruleset. Build one with `puzzleFighter` and override any field.

- `name: string` — Name, for reports.
- `cols: number` — Board width.
- `rows: number` — Visible board height.
- `hiddenRows: number` — Rows above the board that hold gems (the spawn rows).
- `spawnColumn: number` — Column the pair appears in (its axis gem; the original: the fourth column). Blocking it ends the round.
- `colors: number` — Gem colours (2..4 with the pattern letters; more colours need patterns that use them).
- `crashChance: number` — Chance that a dealt gem is a crash gem.
- `diamondEvery: number` — A diamond replaces one gem of every Nth pair (0 = never).
- `dealLength: number` — Pairs generated before the deal repeats.
- `speed: number` — Drop speed 1..5 (the original's VS handicap: five gem drop rates).
- `powerMin: number` — Smallest power gem (width and height).
- `counterTimer: number` — Counter gem countdown.
- `offsetTimer: number` — Countdown of counter gems that still fall after some were offset.
- `remainder: 'random' | 'left'` — Columns that take a partial row of counter gems: chosen at random or filled from the left.
- `pattern: DropPattern` — This board's own drop pattern (what it sends).
- `damage: CrashDamage` — Damage model.
- `timing: CrashGemTiming` — Timings.
- `sequence?: readonly PieceSpec[]` — An authored drop order (puzzles, tests), dealt in order and repeated; replaces the generated deal.
- `seed: number` — Seed for the deal (shared by both boards for an identical drop order) and the board's own randomness.

### `CrashGemSnapshot`

```ts
interface CrashGemSnapshot
```

A whole crash-gem board state: the FallerGame snapshot plus the resolution state.

- `faller: FallerSnapshot` — The pair engine.
- `state: unknown` — Resolution state (plain data).

### `CrashGemTiming`

```ts
interface CrashGemTiming
```

Frame timings of a crash-gem board (60 Hz frames).

- `gravity: readonly number[]` — Frames per row of the falling pair at drop speeds 1..5 (index 0 = speed 1).
- `softDrop: number` — Soft drop in rows per frame.
- `das: number` — Delayed auto shift and auto repeat rate.
- `arr: number` — Auto repeat rate.
- `lockDelay: number` — Frames a landed pair waits before locking (soft drop locks at once).
- `are: number` — Entry delay before the next pair.
- `ready: number` — READY pause.
- `flash: number` — Frames broken gems flash before they go.
- `fall: number` — Frames per row when gems fall after a break.
- `counterFall: number` — Frames per row for falling counter gems.

### `DealMemory`

```ts
interface DealMemory
```

A dealer's memory (carried by snapshots).

- `bag: string[]` — Remaining bag (7-bag).
- `last: string | null` — The last kind dealt (NES reroll).
- `index: number` — Position in a sequence or loop.
- `table: PieceSpec[]` — The generated loop table (Dr. Mario).

### `DealRule`

```ts
type DealRule = | { kind: 'bag'; pieces: readonly string[] } | { kind: 'nes'; pieces: readonly string[] } | { kind: 'uniform'; pieces: readonly string[] } | { kind: 'colors'; piece: string; blocks: number; palette: readonly number[] } | { kind: 'loop'; piece: string; blocks: number; palette: readonly number[]; length: number } | { kind: 'sequence'; items: readonly PieceSpec[]; then?: DealRule }
```

How pieces are dealt.

### `DrMarioOptions`

```ts
interface DrMarioOptions
```

Options for `drMario`.

- `difficulty?: FallerDifficulty` — Difficulty. Arcade: up to 49 speed-ups a level. Normal: up to 20. Easy: up to 10.
- `seed?: number` — Seed.
- `level?: number` — Virus level 0..20 (and beyond, at 84 viruses). Default 0.
- `speed?: 0 | 1 | 2` — Speed: 0 LOW, 1 MED, 2 HI. Default 1.
- `virusCount?: (level: number) => number` — Viruses for a level (default 4 x (level + 1), at most 84).
- `colors?: number` — Colours. Default 3.
- `match?: number` — Match length. Default 4.
- `cols?: number` — Bottle width. Default 8.
- `rows?: number` — Bottle height. Default 16.

### `DropPattern`

```ts
interface DropPattern
```

A counter-gem drop pattern: the colours the attacker's counter gems take, as the opponent sees them (rows top to
bottom; letters R G B Y; the pattern repeats upward and across). Row k of a drop (k = 0 at the bottom) takes the
pattern's k-th row from the bottom, so a small attack always uses the bottom row.

- `name: string` — Display name.
- `rows: readonly string[]` — Rows, top to bottom. Each row is a string of colour letters.
- `sendRate?: (raw: number) => number` — Counter gems actually sent for `raw` counter gems (send-rate handicap). Default: all of them.
- `source?: string` — Where the pattern comes from.

### `FallerAction`

```ts
type FallerAction = 'left' | 'right' | 'softDrop' | 'hardDrop' | 'rotateCW' | 'rotateCCW' | 'rotate180' | 'hold'
```

The input actions.

### `FallerApi`

```ts
type FallerApi = typeof kit
```

`game.faller` — every function and type this pack carries, as one namespace.

### `FallerDifficulty`

```ts
type FallerDifficulty = 'easy' | 'normal' | 'arcade'
```

Easy / Normal / Arcade. Arcade is the original tables; Normal keeps the original handling and the original
early speeds but caps the top speed at a human-playable level; Easy caps it lower (per preset, documented).

### `FallerEvent`

```ts
type FallerEvent = | { type: 'ready' } | { type: 'spawn'; kind: string; serial: number } | { type: 'move'; dx: number } | { type: 'rotate'; dir: number; kick: number } | { type: 'land' } | { type: 'hold'; kind: string } | { type: 'lock'; serial: number; cells: XY[]; tspin: TSpin } | { type: 'lines'; lines: number; rows: number[]; tspin: TSpin; backToBack: boolean; combo: number; perfectClear: boolean; points: number; attack: number } | { type: 'chain'; chain: number; cells: XY[]; cleared: number; colors: number; viruses: number; magic: boolean; points: number; attack: number } | { type: 'moveEnd'; chains: number; points: number; attack: number; viruses: number } | { type: 'score'; points: number; reason: 'softDrop' | 'hardDrop' | 'pushDown' | 'lines' | 'chain' } | { type: 'level'; level: number } | { type: 'speed'; speedIndex: number } | { type: 'allClear' } | { type: 'magic'; color: number; cleared: number } | { type: 'nuisance'; count: number } | { type: 'garbage'; rows: number } | { type: 'stageClear'; level: number } | { type: 'complete' } | { type: 'gameOver'; reason: string }
```

Events reported by `drain()`, in order.

### `FallerInput`

```ts
interface FallerInput
```

One frame of player input. Held states; edges are derived from the previous frame unless `pressed` is given.

- `left?: boolean` — Shift left held.
- `right?: boolean` — Shift right held.
- `softDrop?: boolean` — Soft drop held.
- `hardDrop?: boolean` — Hard drop held (acts on the press).
- `rotateCW?: boolean` — Rotate clockwise held (acts on the press).
- `rotateCCW?: boolean` — Rotate counter-clockwise held (acts on the press).
- `rotate180?: boolean` — Rotate 180 degrees held (acts on the press; only when the ruleset allows it).
- `hold?: boolean` — Hold held (acts on the press).
- `pressed?: Partial<Record<FallerAction, boolean>>` — Explicit press edges for this frame (for presses shorter than a frame). Merged with derived edges.

### `FallerPhase`

```ts
type FallerPhase = 'ready' | 'are' | 'active' | 'clear' | 'fall' | 'stageClear' | 'gameOver' | 'complete'
```

The phase a game is in.

### `FallerRules`

```ts
interface FallerRules
```

A complete ruleset. Build one with a preset (`tetrisGuideline`, `tetrisNes`, `columnsArcade`, `drMario`, `puyoTsu`) and override any field.

- `name: string` — Name, for reports.
- `cols: number` — Well width.
- `rows: number` — Visible well height.
- `hiddenRows: number` — Buffer rows above the well.
- `rotation: RotationSystem` — Pieces and rotation.
- `deal: DealRule` — Randomiser.
- `previews: number` — Pieces shown ahead.
- `hold: boolean` — Hold slot available.
- `hardDrop: boolean` — Hard drop available.
- `rotate180: boolean` — 180-degree rotation input available.
- `initialActions: boolean` — Initial rotation/hold: a rotate or hold pressed during the entry delay applies as the piece appears.
- `match: MatchRule` — Matching rule.
- `matchMinY?: number` — Rows above this one never take part in matches (Puyo's hidden 13th row). Default: every row matches.
- `vanishAboveY?: number` — Cells that come to rest above this row vanish (Puyo's 14th row).
- `cascade: 'rows' | 'cells' | 'linked'` — Gravity after clears: 'rows' collapses cleared rows (Tetris), 'cells' drops each cell, 'linked' keeps capsule halves joined.
- `timing: FallerTiming` — Timings.
- `scoring: ScoringFn` — Scoring rule.
- `attack?: (e: LinesEvent) => number` — Attack sent for a rows clear (versus); omitted = 0.
- `progression: ProgressionRule` — Level progression.
- `startLevel: number` — Starting level.
- `startScore?: number` — Starting score (Columns start-level bonus).
- `speed?: number` — Speed setting passed to scoring (Dr. Mario 0/1/2).
- `startSpeedIndex?: number` — Starting speed index (Dr. Mario: LOW 15, MED 25, HI 31).
- `topOut: TopOutRule` — Top-out rules.
- `viruses?: VirusRule` — Viruses (Dr. Mario).
- `magic?: MagicRule` — Magic jewel (Columns).
- `nuisance?: NuisanceRule` — Nuisance (Puyo).
- `objective: Objective` — Victory condition.
- `scoreCap?: number` — Score cap (NES: 999999).
- `layout?: readonly string[]` — Authored starting stack: rows of characters, bottom-aligned; '.' empty, digits are colours, 'n' nuisance, 'g' garbage, and letters map through `layoutColors`.
- `layoutColors?: Record<string, number>` — Letter-to-colour map for `layout` (e.g. { R: 0, G: 1, B: 2, Y: 3, P: 4 }).
- `seed: number` — Seed.

### `FallerSnapshot`

```ts
interface FallerSnapshot
```

The whole mutable state of a game: plain data, so a snapshot is a deep copy.

- `frame: number` — Frame counter.
- `phase: FallerPhase` — Phase.
- `timer: number` — Frames left in the phase.
- `timerTotal: number` — Phase length.
- `cells: (Cell | null)[]` — Well cells.
- `nextId: number` — Next cell id.
- `rng: RngState` — Where the well's stream stands (viruses, nuisance columns, garbage holes): a kernel `Rng` snapshot.
- `dealRng: RngState` — Where the piece deal's stream stands (kept separate so two games on one seed get the same pieces).
- `dealer: DealMemory` — Dealer memory.
- `queue: PieceSpec[]` — Upcoming pieces.
- `held: PieceSpec | null` — Held piece.
- `holdUsed: boolean` — Hold used since the last lock.
- `active: Active | null` — Falling piece.
- `serial: number` — Piece serial counter.
- `acc: number` — Gravity accumulator.
- `lockTimer: number` — Lock timer.
- `lockResets: number` — Lock resets used.
- `lowestY: number` — Lowest row the piece has reached.
- `landed: boolean` — The piece has touched the stack at least once.
- `lastRotate: boolean` — The last successful action was a rotation.
- `lastKick: number` — Kick test index of the last rotation.
- `rotMemory: RotationMemory` — Rotation memory (Puyo quick turn).
- `prev: Record<FallerAction, boolean>` — Held inputs last frame.
- `dasDir: number` — Auto-repeat direction.
- `dasCounter: number` — Auto-repeat counter.
- `arrCounter: number` — ARR counter.
- `downArmed: boolean` — NES soft drop armed by a fresh press.
- `downCounter: number` — NES soft-drop counter.
- `pushDown: number` — NES push-down rows.
- `bufferedRotate: number` — Buffered initial rotation (0 none).
- `bufferedHold: boolean` — Buffered initial hold.
- `score: number` — Score.
- `level: number` — Level.
- `lines: number` — Lines cleared (rows games).
- `cleared: number` — Cells cleared (matching games: jewels, puyos).
- `pieces: number` — Pieces locked.
- `dealtThisLevel: number` — Pieces dealt into play this level (Dr. Mario speed-ups).
- `speedIndex: number` — Speed index.
- `speedUps: number` — Speed-ups this level.
- `combo: number` — Combo counter (-1 = none).
- `backToBack: boolean` — Back-to-back armed.
- `chain: number` — Current chain step in this move.
- `bestChain: number` — Best chain this game.
- `movePoints: number` — Points this move.
- `moveAttack: number` — Attack this move.
- `moveViruses: number` — Viruses cleared this move.
- `lastLines: number` — Lines cleared by the last piece.
- `lockRow: number` — Row of the last lock.
- `clearing: { cells: XY[]; rows: number[]; magic: boolean } | null` — Cells being cleared.
- `falling: [number, number][] | null` — Cells falling: id -> rows.
- `pendingNuisance: number` — Nuisance waiting to fall.
- `nuisanceCarry: number` — Fractional nuisance carried between chains.
- `allClearBonus: boolean` — The next chain carries the all-clear bonus.
- `nuisanceDropped: boolean` — Nuisance has fallen this turn.
- `pendingGarbage: { rows: number; hole: number }[]` — Garbage waiting (rows games).
- `viruses: number` — Viruses left.
- `virusesStart: number` — Viruses at the start of the level.
- `stats: Record<string, number>` — Pieces dealt by kind (NES statistics).
- `magicCooldown: number` — Pieces before a magic column may appear again.
- `targetPoints: number` — Target points (Puyo; a versus layer can lower it for margin time).
- `reason: string` — Why the game ended.
- `goalProgress: number` — Objective progress: best value toward the goal.
- `events: FallerEvent[]` — Pending events.

### `FallerTiming`

```ts
interface FallerTiming
```

All the frame timings of a ruleset. Values are 60 Hz frames.

- `gravity: (ctx: TimingContext) => number` — Gravity in rows per frame for the current state (1/48 = one row every 48 frames; 20 = instant).
- `softDrop: SoftDropTiming` — Soft drop.
- `shift: ShiftTiming` — Auto-repeat.
- `lock: LockTiming` — Locking.
- `are: number | ((ctx: TimingContext) => number)` — Entry delay after a lock (or after the line clear) before the next piece appears.
- `lineClear: number | ((ctx: TimingContext) => number)` — Line-clear delay (rows games).
- `matchFlash: number` — Frames a matched set flashes before it is removed (matching games).
- `fall: number` — Frames per row of cascade gravity after a clear (and for split pieces).
- `nuisanceFall: number` — Frames per row for falling nuisance.
- `spawnDrop: boolean` — Guideline: a new piece drops one row as soon as it appears, if it can.
- `ready: number` — Frames of the READY pause before the first piece.
- `stageClear: number` — Frames of the stage-clear pause (Dr. Mario).
- `speedUp?: SpeedUpRule` — Dr. Mario speed-ups: the speed index rises every `every` pieces dealt, at most `max` times per level.

### `FitsFn`

```ts
type FitsFn = (cells: readonly XY[]) => boolean
```

Collision callback: true when every given cell is free and inside the well.

### `GemType`

```ts
type GemType = 'normal' | 'crash' | 'diamond' | 'counter'
```

What a cell on a crash-gem board is.

### `GuidelineOptions`

```ts
interface GuidelineOptions
```

Options for `tetrisGuideline`.

- `difficulty?: FallerDifficulty` — Difficulty. Arcade: the full curve to 20G. Normal: gravity capped at the level-12 speed. Easy: capped at level 8, 1 s lock delay.
- `seed?: number` — Seed.
- `startLevel?: number` — Start level, 1..15. Default 1.
- `goal?: number` — Lines to finish (Marathon: 150). 0 = endless. Default 150.
- `previews?: number` — Next-queue length. Default 5.
- `hold?: boolean` — Hold. Default true.
- `hardDrop?: boolean` — Hard drop. Default true.
- `rotate180?: boolean` — Allow a 180-degree rotate input (not in SRS proper). Default false.
- `das?: number` — Delayed auto shift in frames. Default 10 (the Guideline's recommended 167 ms).
- `arr?: number` — Auto repeat rate in frames. Default 2 (33 ms).
- `are?: number` — Entry delay in frames. Default 6 (the Guideline's recommended ARE).
- `lineClear?: number` — Line-clear delay in frames. The Guideline leaves it to each game; default 24 (est.).
- `lockDelay?: number` — Lock delay in frames. Default 30 (0.5 s).
- `lockResets?: number` — Move resets before a forced lock. Default 15.
- `perfectClear?: boolean` — Score perfect clears (later Guideline games). Default false.
- `cols?: number` — Well width. Default 10.
- `rows?: number` — Visible well height. Default 20.

### `GuidelineScoringOptions`

```ts
interface GuidelineScoringOptions
```

Options for `guidelineScoring`.

- `perfectClear?: boolean` — Add the perfect-clear bonus used by some Guideline games (800/1200/1800/2000, 3200 for a B2B tetris). Default false.

### `HardDropEvent`

```ts
interface HardDropEvent
```

Rows moved by a hard drop.

- `type: 'hardDrop'` — Event kind.
- `rows: number` — Rows moved.
- `level: number` — Current level.

### `LineMatch`

```ts
interface LineMatch
```

Line-of-N matching result: groups by colour plus the Columns "lines of three" count.

- `groups: MatchGroup[]` — One group per colour, every cell that is part of a qualifying run.
- `linesOfN: number` — Sum over every maximal run of (length - (n - 1)): a run of 4 counts as two lines of three.

### `LinesEvent`

```ts
interface LinesEvent
```

A piece locked in a rows game (Tetris), with or without lines.

- `type: 'lines'` — Event kind.
- `lines: number` — Lines cleared by this piece.
- `tspin: TSpin` — T-spin classification of the lock.
- `difficult: boolean` — True when this clear is "difficult" (four or more lines, or a T-spin that cleared lines).
- `backToBack: boolean` — True when the previous line clear was also difficult (back-to-back applies).
- `combo: number` — Consecutive line-clearing pieces minus one (0 for the first, -1 when this piece cleared nothing).
- `perfectClear: boolean` — True when the clear left the well empty.
- `levelBefore: number` — Level before this clear.
- `levelAfter: number` — Level after this clear's lines are counted.

### `Link`

```ts
type Link = 'left' | 'right' | 'up' | 'down'
```

Which neighbour a capsule half is joined to (Dr. Mario), or undefined for a free cell.

### `LockTiming`

```ts
interface LockTiming
```

Locking rule.

- `mode: 'move' | 'step' | 'gravity'` — 'move': lock delay that moves and rotations reset, up to `resets` times (restored on reaching a new lowest row; Guideline extended placement). 'step': lock delay reset only by falling a row. 'gravity': lock as soon as a gravity or soft-drop step is blocked (NES Tetris, Dr. Mario).
- `delay: number` — Frames a grounded piece waits before locking.
- `resets: number` — Maximum resets: 'move' mode counts moves and rotations on the ground; 'step' mode counts floor kicks that lift a landed piece (which would otherwise allow endless stalling). 0 = unlimited in 'step' mode.
- `softDropLocks?: boolean` — Holding soft drop on a grounded piece locks it at once (Puyo, Columns).

### `MagicRule`

```ts
interface MagicRule
```

Columns' magic jewel.

- `dangerRows?: number` — Offer a magic column when the stack has reached within this many rows of the top.
- `every?: number` — Also offer one every N pieces (0 = never).
- `cooldown: number` — Pieces before another can be offered.
- `minLevel?: number` — Lowest level at which it can appear.

### `MatchGroup`

```ts
interface MatchGroup
```

A matched set of cells found after a lock.

- `cells: XY[]` — Cells in the group.
- `color: number` — Their colour (-1 for full rows).

### `MatchRule`

```ts
type MatchRule = | { kind: 'rows' } | { kind: 'lines'; length: number; diagonals: boolean } | { kind: 'groups'; size: number }
```

What counts as a match after a lock.

### `NesOptions`

```ts
interface NesOptions
```

Options for `tetrisNes`.

- `difficulty?: FallerDifficulty` — Difficulty. Arcade: the full table to the 1-frame level 29. Normal: never faster than level 18 (3 frames a row). Easy: never faster than level 9 (6).
- `seed?: number` — Seed.
- `startLevel?: number` — Start level 0..19 (the NES menu offers 0-9, and 10-19 with A held). Default 0.
- `cols?: number` — Well width. Default 10.
- `rows?: number` — Visible well height. Default 20.
- `preview?: boolean` — Show the next piece (the NES SELECT toggle). Default true.

### `NuisanceRule`

```ts
interface NuisanceRule
```

Puyo nuisance rules (used by the versus layer).

- `maxPerDrop: number` — Most nuisance that falls after one piece (Tsu: 30, five rows of six).
- `targetPoints: number` — Score per nuisance sent (Tsu: 70).
- `allClearBonus: number` — Extra nuisance sent on the chain after an all clear (Tsu: 30).

### `Objective`

```ts
type Objective = | { kind: 'endless' } | { kind: 'lines'; lines: number } | { kind: 'chain'; chain: number; pieces?: number } | { kind: 'allClear'; pieces?: number } | { kind: 'clearColor'; color: number; pieces?: number } | { kind: 'score'; score: number; pieces?: number }
```

A goal that ends the game in victory.

### `PieceBlock`

```ts
interface PieceBlock
```

One block of a piece, relative to the piece origin.

- `dx: number` — Column offset from the piece origin.
- `dy: number` — Row offset from the piece origin (y down).
- `color: number` — Colour index.
- `link?: Link` — The partner this block is joined to, for pieces whose halves stay joined after locking (capsules).

### `PiecePose`

```ts
interface PiecePose
```

A piece's position and orientation.

- `rot: number` — Rotation state index.
- `x: number` — Origin column.
- `y: number` — Origin row.
- `colors: number[]` — Block colours in order (cycling systems change these instead of the shape).

### `PieceSpec`

```ts
interface PieceSpec
```

What the randomiser deals: a piece kind and its colours (one per block for coloured pieces).

- `kind: string` — The piece kind, e.g. 'T', 'pair', 'capsule', 'column'.
- `colors: number[]` — Colours, one per block (or one shared colour for tetrominoes).
- `magic?: boolean` — Columns' magic jewel column: clears every jewel of the colour it lands on.

### `PlacementPreview`

```ts
interface PlacementPreview
```

What placing a piece would do, from `FallerGame.preview`.

- `ok: boolean` — The placement fits.
- `points: number` — Points it would score (drops, clears, chains).
- `chains: number` — Longest chain it would set off.
- `attack: number` — Attack it would send (nuisance or garbage lines).
- `lines: number` — Lines it would clear (rows games).
- `over: boolean` — It would end the game.
- `field: (Cell | null)[]` — The resulting well cells (row-major from the top of the buffer).

### `PowerGem`

```ts
interface PowerGem
```

A power gem: a fused rectangle of one colour.

- `id: number` — Power gem id (stable while it exists; changes when it grows).
- `color: number` — Colour.
- `x: number` — Left column.
- `y: number` — Top row.
- `w: number` — Width in cells.
- `h: number` — Height in cells.

### `ProgressionRule`

```ts
type ProgressionRule = | { kind: 'lines'; perLevel: number; base: number; maxLevel?: number; nesFirst?: boolean } | { kind: 'cleared'; perLevel: number; maxLevel?: number } | { kind: 'pieces'; perLevel: number; maxLevel?: number } | { kind: 'viruses'; maxLevel?: number } | { kind: 'none' }
```

How the level advances.

### `PushDownEvent`

```ts
interface PushDownEvent
```

NES push-down points: rows of the final continuous soft drop, added when the piece locks.

- `type: 'pushDown'` — Event kind.
- `rows: number` — Rows moved.
- `level: number` — Current level.

### `PuyoMission`

```ts
interface PuyoMission
```

A Puyo mission (a "nazo puyo" style puzzle): a starting stack, the pairs to play, and a goal.

- `name: string` — Short name.
- `text: string` — The goal, shown to the player.
- `layout: readonly string[]` — Starting stack, bottom-aligned rows of R G B Y P (and n for nuisance).
- `pairs: readonly string[]` — The pairs, as two letters each: axis then child (e.g. 'RG').
- `goal: Objective` — The objective (with a piece limit).

### `PuyoOptions`

```ts
interface PuyoOptions
```

Options for `puyoTsu`.

- `difficulty?: FallerDifficulty` — Difficulty. Arcade: Tsu Normal's four colours, full speed curve. Normal: four colours, speed capped at level 8. Easy: three colours (Tsu Easy), capped at level 4.
- `seed?: number` — Seed.
- `colors?: number` — Colours dealt (3 Easy, 4 Normal, 5 Hard in Tsu).
- `popSize?: number` — Group size that pops. Default 4.
- `piecesPerLevel?: number` — Endless: pieces per speed level. Default 30.
- `mission?: number | PuyoMission` — A mission instead of endless play (index into `PUYO_MISSIONS`, or your own).
- `cols?: number` — Well width. Default 6.
- `rows?: number` — Visible well height. Default 12.

### `PuzzleFighterOptions`

```ts
interface PuzzleFighterOptions
```

Options for `puzzleFighter`.

- `difficulty?: 'easy' | 'normal' | 'arcade'` — Easy / Normal / Arcade. Arcade: the given drop speed. Normal: one slower (min 1). Easy: speed 1 and longer lock delay.
- `seed?: number` — Seed.
- `pattern?: string | DropPattern` — Drop pattern key in `DROP_PATTERNS`, or your own. Default 'bands'.
- `speed?: number` — Drop speed 1..5. Default 3.
- `diamond?: number` — Diamond damage factor: 0.5 original, 0.8 HD Remix.
- `cols?: number` — Board width. Default 6.
- `rows?: number` — Board height. Default 12.
- `colors?: number` — Colours. Default 4.
- `crashChance?: number` — Crash gem chance per gem. Default 0.125 (estimate).
- `diamondEvery?: number` — Diamond every N pairs (0 = off). Default 25.
- `powerMin?: number` — Smallest power gem side. Default 2.

### `RotationMemory`

```ts
interface RotationMemory
```

Per-piece rotation state the engine keeps between rotations (Puyo's quick-turn flag).

- `quickTurn: boolean` — Set by a blocked rotation of a wedged vertical pair; the next press turns it 180 degrees.

### `RotationResult`

```ts
interface RotationResult extends PiecePose
```

The result of a successful rotation. `kick` is the index of the kick test used (0 = no offset).

- `kick: number` — Index of the kick test that succeeded (0 = the plain rotation).

### `RotationSystem`

```ts
interface RotationSystem
```

A rotation system: shapes, spawn rule and rotation resolution for a family of pieces.

- `readonly id: string` — Identifier, e.g. 'srs', 'nrs', 'cycle', 'pair', 'capsule'.
- `readonly kinds: readonly string[]` — The piece kinds this system defines, in their canonical order.
- `states(kind: string): number` — Number of rotation states for a kind.
- `blocks(kind: string, pose: PiecePose): PieceBlock[]` — The blocks of a piece at a pose.
- `spawn(spec: PieceSpec, cols: number): PiecePose` — Where a piece spawns in a well `cols` wide.
- `rotate(kind: string, pose: PiecePose, dir: 1 | -1 | 2, fits: FitsFn, memory: RotationMemory): RotationResult | null` — Resolve a rotation: `dir` 1 = clockwise, -1 = counter-clockwise, 2 = 180 degrees. Null when it fails.
- `spinCentre?(kind: string, pose: PiecePose): XY | null` — The centre of a piece's bounding box for the 3-corner T-spin test, or null if the kind has none.

### `ScoringEvent`

```ts
type ScoringEvent = SoftDropEvent | HardDropEvent | PushDownEvent | LinesEvent | ChainEvent
```

Everything a scoring function is asked to price.

### `ScoringFn`

```ts
type ScoringFn = (event: ScoringEvent) => number
```

A scoring rule: points for an event (0 for events it does not score).

### `ShiftTiming`

```ts
interface ShiftTiming
```

Horizontal auto-repeat. `modern` = DAS then ARR; `nes` = the NES counter (shift at 16, reload 10, charged by a wall).

- `style: 'modern' | 'nes'` — Style of auto-repeat.
- `das: number` — Frames before auto-repeat starts (NES: 16).
- `arr: number` — Frames between repeats (0 = instantly to the wall; NES: 6).
- `chargeInDelay: boolean` — Keep charging DAS while no piece is in play (ARE, line clear). NES freezes it.
- `blockedBySoftDrop?: boolean` — NES: left/right do nothing while soft drop is held.

### `SoftDropEvent`

```ts
interface SoftDropEvent
```

Rows moved by a soft drop (Guideline, Columns, Puyo: scored as they happen).

- `type: 'softDrop'` — Event kind.
- `rows: number` — Rows moved.
- `level: number` — Current level.

### `SoftDropTiming`

```ts
type SoftDropTiming = | { kind: 'factor'; factor: number; min?: number } | { kind: 'rate'; rowsPerFrame: number } | { kind: 'nes'; first: number; repeat: number }
```

Soft drop speed.

### `SpeedUpRule`

```ts
interface SpeedUpRule
```

Speed-ups within a level (Dr. Mario).

- `every: number` — Pieces dealt between speed-ups.
- `max: number` — Most speed-ups per level.

### `TableRotationOptions`

```ts
interface TableRotationOptions
```

Options for a table-driven rotation system (`tableRotation`).

- `id: string` — Identifier reported by `RotationSystem.id`.
- `shapes: Record<string, XY[][]>` — Shapes per kind, one list of cells per rotation state, in clockwise order.
- `colors?: Record<string, number>` — Colour per kind (tetrominoes are one colour). Defaults to the kind's index.
- `spawnRot?: Record<string, number>` — Spawn rotation per kind. Default 0.
- `spawnMode: 'box' | 'pivot'` — Spawn origin. 'box' centres the bounding box (rounded left) with its top at `spawnY` (SRS); 'pivot' places the pivot at column floor(cols / 2), row `spawnY` (NES).
- `spawnY: number` — Spawn row of the origin.
- `kicks?: (kind: string, from: number, to: number) => readonly (readonly [number, number])[]` — Kick tests for a rotation, in y-DOWN cell offsets, tried in order. Default: only [0, 0].
- `spinCentres?: Record<string, XY>` — Bounding-box centre per kind for the 3-corner T-spin test.

### `TimingContext`

```ts
interface TimingContext
```

Context passed to timing functions.

- `level: number` — Current level.
- `speedIndex: number` — Current speed index (Dr. Mario speed-ups; otherwise 0).
- `pieces: number` — Pieces locked so far.
- `frame: number` — Frame counter.
- `lockRow: number` — Row of the last lock (piece origin, 0 = top visible row).
- `rows: number` — Visible rows in the well.
- `lines: number` — Lines cleared by the last piece (rows games).

### `TopOutRule`

```ts
interface TopOutRule
```

Top-out rules.

- `blockOut?: boolean` — Game over when a new piece overlaps the stack (Tetris, Dr. Mario, Columns).
- `lockOut?: boolean` — Game over when a piece locks entirely above the visible well (Guideline).
- `deathCells?: readonly XY[]` — Game over when any of these cells is filled after a move resolves (Puyo: column 3 of the top row).
- `overflow?: boolean` — Game over when anything is left above the visible well after a move resolves (Columns).

### `TSpin`

```ts
type TSpin = 'none' | 'mini' | 'full'
```

How a T-spin was classified at lock (Guideline 3-corner rule with the pointing-side mini test).

### `VirusRule`

```ts
interface VirusRule
```

Dr. Mario virus placement.

- `count?: (level: number) => number` — Viruses for a level. Default min(84, 4 x (level + 1)).
- `maxRow?: (level: number) => number` — Highest row (1 = bottom) a virus may occupy at a level (NES table: 10, then 11/12/13 from level 15).
- `palette: readonly number[]` — Virus colours.
- `spacing?: boolean` — The NES distance-two colour rule (no virus shares a colour with the cells two away in each direction).

### `XY`

```ts
interface XY
```

A grid coordinate: x is the column (0 = left), y is the row (0 = top visible row; hidden rows are negative).

- `x: number` — Column, 0 = left.
- `y: number` — Row, 0 = the top visible row; rows above the well are negative.

---

## For AI agents: Phaser AE

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