collin/mahjong

a8f341f64cb464e7603cab4610af982b153a7916 / README.md

1	# 台灣麻將 — four-player hotseat on one touchscreen
2
3	Sixteen-tile Taiwanese mahjong for four people sitting around a single laptop.
4	All four hands are on screen at once, each rotated to face its own edge — put a
5	piece of card or plastic over your strip so the others can't see your tiles.
6	Every label is Chinese with English underneath; the tiles themselves stay
7	Chinese, because that is what the tiles say.
8
9	Nobody else around? 單人對局 Single player on the lobby gives you the
10	bottom seat and hands the other three to the computer — same rules, same
11	table, same scoring. See [computer players](#computer-players).
12
13	```
14	npm install
15	npm run dev # then open the browser full-screen (F11)
16	npm test # rules engine, the bots, and 200 randomly-played hands
17	```
18
19	## Screen layout
20
21	```
22	┌──── 對家 (rotated 180°) ────┐
23	上家 (rotated 90°) │ wall, and the discard pool │ 下家 (rotated −90°)
24	└──── 自家 (upright, near you) ┘
25	```
26
27	Seat 0 is the bottom edge, and play runs 0 → 1 (right) → 2 (top) → 3 (left),
28	which is the normal counter-clockwise 東南西北 order.
29
30	Each strip shows, from the player's edge inwards: nameplate (seat wind, 莊
31	marker, 聽 badge, chip count) → concealed hand → action buttons → melds and
32	flowers. Discards are not in the strips: they are thrown into the middle and
33	stay there for the hand, the way they would be on a table. (A phone has no
34	middle to throw into, so the compact layout keeps a discard row per seat — see
35	[on a phone](#on-a-phone).)
36
37	## Playing
38
39	- The tile you just drew is held apart from the sorted hand with a gold ring
40	and a 摸 label, instead of being sorted invisibly into it. It merges into the
41	hand once you discard. 補花 replacements and kong replacements are marked the
42	same way.
43	- The wall is drawn in the centre as a square of four staggered sides, laid
44	out like a `#` with the corners open, the way it's built on a real table. The
45	gold stack is the break point you draw from, stacks shrink to a single tile and
46	then vanish as they're used, and the dimmed tail is the 16-tile 底牌 that ends
47	the hand — which is also the end kong and flower replacements are taken from,
48	so the square is eaten from both directions at once. Only what is still
49	standing is drawn, and it is evened up over the four sides as it goes, which
50	is what lets every tile left in it be the size of a tile in your hand — see
51	[what is left of the wall](#what-is-left-of-the-wall).
52	- Discard — drag a tile out of your row and it comes up out of your hand and
53	follows your finger anywhere on the table; let go and it goes in, from where
54	you let go and at the speed you let go at. Dragging along the row is still
55	arranging your hand — which of the two you meant is decided once, from whether
56	the movement is mostly along the row or out of it, and then it sticks. Let go
57	back over your own hand and the tile goes back. Tapping a tile twice, or the
58	打出 button, still works and lobs it in for you.
59	- The discard pool — every tile thrown lands in the middle and stays there
60	until the hand ends, with real weight: it skids, turns, knocks the tiles
61	already there out of its way, and comes to rest against them. Nothing is ever
62	stacked on anything — tiles are solved as rectangles, so two lying at an angle
63	lean on each other rather than overlapping. The tile still to be claimed is
64	the lit one.
65	- Over the wall or across the table — which of the two ways a tile goes in is
66	not a setting, it is whatever the wall allows. At the start of a hand the
67	square is a solid barrier and a discard has to be lobbed over it, so the
68	flick's speed decides how far across the pool it lands. As the wall is eaten
69	away, gaps open in front of one seat and then another, and from then on that
70	seat can slide a tile in instead — flat across the cloth at exactly the speed
71	it was flicked. Which it will be is a ray cast at the stacks actually standing
72	there, so a gap off to one side counts, and a stack worn down to a single tile
73	is low enough to go over. A seat whose wall is still up says 牆未開 on its
74	nameplate, so a lob is never a mystery.
75	- Throw it too hard and it comes off the pool and into somebody's tiles —
76	the middle stops exactly where their hand starts. Their row takes the knock
77	and rocks back, and with 報牌 on they tell you about it (喂，小心點). Never
78	your own edge: you cannot be barged by your own discard.
79	- Arranging — drag any tile in your hand to reorder it; 理牌 sorts it back
80	into suit order. Hands are never auto-sorted after the deal, so an arrangement
81	you set up survives draws, claims and kongs.
82	- Rules — the `?` on your nameplate opens a bilingual rules panel anchored to
83	your own edge of the table and rotated to face you.
84	- Claiming — after a discard, every seat that can claim gets 胡 / 槓 / 碰 /
85	吃 / 過 buttons on their own strip, and they resolve by priority (胡 > 槓/碰 >
86	吃; ties go to the player nearest the discarder in turn order).
87	The table never blocks on a claim. The next player gets a 摸牌 button and
88	may draw whenever they like, which shuts the window on anyone who hasn't
89	called — exactly like shouting 碰 before the next player picks up. A claim
90	already declared still stands, so calling in time always wins the tile. If
91	everyone answers first, play advances on its own without the extra tap.
92	The seat that draws next gets no separate 過 button, because for them the two
93	are the same move: picking up is how you decline. Their draw button reads
94	過．摸牌 while they have something they could have called instead. Wanting to
95	decline but leave the window open for everyone else is just waiting, which is
96	what not pressing anything already does.
97	- On your turn — 自摸, 暗槓 and 加槓 appear automatically when legal.
98	加槓 offers everyone else a 搶槓 chance.
99	- Where the buttons go — the strip is built from its edge inwards, so the
100	action bar holds a fixed height whether or not anything is in it. Otherwise
101	the melds above it shuffled along every time you lifted a tile
102	and 打出五萬 appeared, since a button naming a tile stands taller than a bare
103	過. Every button on the bar is given that one height for the same reason.
104	- When a hand ends — a big arrow drops onto the winner's edge of the table.
105	It lives inside their strip, so it turns with the seat and lands on the right
106	person wherever they are sitting, and 一炮多響 lights up every seat that
107	called. A 流局 has no winner to point at, so it turns the hands over instead:
108	who was 聽牌 and the tiles they were waiting on, the same reveal as at a real
109	table.
110	- Undo — a 復原 button in the middle of the table takes back the last
111	action, naming what it will undo (`復原玩家 2 打五萬`). It sits in the
112	centre rather than on a seat because whoever spots the mis-tap should be
113	able to reach it. Twenty actions deep, cleared when the next hand is dealt.
114	Snapshots live outside the saved state, so an undo does not survive a
115	refresh: what you can take back is what happened while everyone was still
116	watching it happen.
117	- Sound — on by default, muted from the 🔊 button in the middle of the
118	table or from settings. A dry clack as a tile goes down, and a distinct
119	two-note chime when a claim window opens, which is how a slow player notices
120	their 碰 is available before the next player draws it shut. Everything is
121	synthesised with a few oscillators (`src/game/sound.ts`) rather than sampled,
122	so there is nothing to load and the cue lands on the same frame as the tile.
123	Browsers refuse to start audio before the page has been clicked, so the first
124	sound anyone hears is the deal — triggered by the button that starts it.
125	- 報牌 (voice) — a second switch under sound calls the game out loud: 碰,
126	吃, 槓, 胡了, 自摸, and the name of every tile as it is discarded — 三條,
127	五萬, 東風. A flower says 補花 and then which one. A new call cuts off one
128	still being spoken; at table pace the newest is the only one that matters.
129	See [the voice pack](#the-voice-pack) for where the audio comes from.
130	- Settings — 設定 from the lobby, or from the game-over panel: player names,
131	底 / 台 / starting chips, the house-rule switches below, and sound. Kept in
132	`localStorage` separately from the save, so they carry over to the next game.
133	Stakes are locked once a game is under way — they'd otherwise rewrite chips
134	already won.
135
136	## On a phone
137
138	The table assumes four people sitting around a screen lying flat, and about
139	770px in both directions before the middle is worth looking at. A phone has
140	neither, so under `(max-height: 620px), (max-width: 820px)` it switches to the
141	compact layout: nothing is rotated, everything reads upright for the one person
142	holding it, the other three seats shrink to cards showing what is public about
143	them, and the depth that frees up goes to your hand, which is allowed to wrap.
144
145	There is no centre square there — the middle collapses to a one-line bar showing
146	what the wall square was telling you anyway — so there is nowhere to throw a tile
147	to. The compact layout therefore keeps a discard row per seat, and discarding
148	is tap-twice or 打出, exactly as it was. The pool and the throw are a full-size
149	feature.
150
151	The breakpoint is written down once, in `COMPACT_QUERY` in `src/ui/compact.ts`,
152	which sets a `compact` class on `<html>` for the CSS to key off.
153
154	## Computer players
155
156	Single player seats you at the bottom and gives seats 1-3 to the computer.
157	Their tiles go face down and their 聽 / 過水 badges come off, since both would
158	give the hand away; everything public — the pool, melds, flowers, chips — stays
159	exactly as it is, and everyone turns their hand over when the hand ends. They
160	throw their tiles in like anyone else, and under the same rule: a computer seat
161	whose wall is open slides them across, and one still walled in lobs them over.
162
163	The engine does not know the bots exist. `AutoPlay` (`src/game/autoplay.ts`)
164	watches the same state the screen does, and when the seat being waited on
165	belongs to the computer it calls the identical method the button would have
166	called — `discard`, `respond`, `declareConcealedKong`. So scoring, sound,
167	saving, 過水 and 包牌 all work without a special case, and a bot cannot make a
168	move a person could not. It never acts for you and never closes your claim
169	window: if the table is waiting on you, it waits.
170
171	How they play (`src/game/bot.ts`) is one idea applied everywhere. A hand is
172	judged at its resting size — the (5 − melds) × 3 + 1 tiles you hold between a
173	discard and your next draw — by its 向聽 first and by its 進張 count second.
174
175	- Discard — try every distinct tile, keep the one that leaves the best
176	resting hand. Ties go to whatever is hardest to build on: a lone honour with
177	most of its copies already gone, before a lone 五萬 that still has neighbours
178	to meet.
179	- 碰 / 吃 — only when the hand that comes out the other side is strictly
180	closer to home. Melding costs concealment and flexibility, so a claim that
181	merely holds the 向聽 steady is declined — which is why the bots pass on
182	pungs that would narrow a two-sided wait to a single tile.
183	- 槓 — judged more kindly: it pays 台 and fetches a replacement, so standing
184	still is good enough.
185	- 胡 — always taken.
186
187	What they watch you do (`src/game/danger.ts`) is the other half. Efficiency
188	alone throws whatever is fastest and pays for it; these bots read the table
189	first, off the face-up table only — discard rows, exposed melds, the 過水 locks
190	the nameplates already show. Two separate questions:
191
192	- How close does each seat look? Turns taken (a hand is usually settled
193	inside ten goes each, long before the wall looks finished, so counting the
194	wall is the wrong clock), melds exposed, and what they have been throwing
195	lately. Nobody discards 五條 out of a hand that still needs shaping — it comes
196	out once the shape is done, so late middle tiles are the tell. A 過水 lock is
197	a confession: to be locked out of a tile you had to have been able to win on
198	it.
199	- How likely is this tile the one they want? An honour can only be caught by
200	a pair or a triplet; a 五萬 sits in the middle of every run through it. A tile
201	they discarded themselves was not their tile when it went down — not proof
202	now, but the best evidence there is. A tile with no copies left unseen cannot
203	be a pair or triplet wait at all. Two melds in one suit means stay out of that
204	suit. And two dragon pungs down means the third dragon is not going anywhere
205	near the table, because 包牌 bills the feeder for the entire hand.
206
207	Whether any of that changes the discard depends on the bot's own hand. At 聽牌
208	it pushes — nothing short of 包牌 is worth breaking a ready hand for. Two or
209	three away with somebody live across the table and it will give up a whole 向聽
210	step to throw something safe, which is what folding is.
211
212	The estimate is checked against ground truth in the tests rather than assumed:
213	over the tiles bots actually considered, the ones the model rated below 0.2 deal
214	in 0% of the time and the ones above 0.8 deal in 10.5%, cleanly monotonic in
215	between. Switching the read on cuts deal-ins by about 13% over a few hundred
216	hands, takes hands from ~30 discards to ~38, and moves the draw rate from
217	almost nothing to about one hand in ten — which is what a table where people
218	stop feeding each other actually looks like.
219
220	What they know is still only what they can see. `unseenFor` counts the four
221	copies of each tile and subtracts the bot's own hand plus every discard and
222	exposed meld on the table. Neither module ever reads an opponent's concealed
223	tiles or looks at the wall.
224
225	There is no difficulty setting, and the reading stops at the discard: claims are
226	still judged purely on speed, and a bot will take a 碰 that walks it into
227	trouble.
228
229	向聽 lives in `src/game/shanten.ts`, apart from `hu.ts`, because the two want
230	different things: the win check has to be exact, and this one has to be fast —
231	it runs a few hundred times for every discard a bot considers. The tests hold
232	them against each other over random hands, since they work in completely
233	different ways and any disagreement is a bug in the fast one.
234
235	Undo behaves differently against the computer: rewinding into the middle of its
236	turn would only hand the move straight back to it, so one press goes back to
237	the last point you had a decision to make, computer replies and all.
238
239	## Saving
240
241	The game state is plain data, so a save is just its JSON in `localStorage`,
242	rewritten after every move. Close the lid, refresh, or run the battery flat and
243	nothing is lost — the lobby offers 繼續對局 Resume above the two ways to
244	start a fresh one, showing whether it was a solo or a hotseat game, the round,
245	hand number, chip counts and when it was saved. Which seats the computer holds
246	is part of the state, so a save resumes as the kind of game it was. A
247	save is validated before it is offered (four players, 144 tiles accounted for),
248	so a truncated or hand-edited one is ignored rather than loaded into a broken
249	table. `VERSION` in `save.ts` retires old saves if the state shape changes.
250
251	## Rules implemented
252
253	- 144 tiles (four of each suit/honour, eight flowers), 16-tile hands, dealer
254	draws the 17th.
255	- 補花 at the deal and on every drawn flower, replacements from the back of the
256	wall.
257	- 吃 only from 上家; 碰/槓/胡 from anyone. 明槓, 暗槓, 加槓, 搶槓, 槓上開花.
258	- 流局 when 16 tiles remain (`Rules.wallReserve`); the dealer keeps the deal on a
259	draw or on a dealer win (連莊), otherwise the deal passes and the round wind
260	advances every four passes. A full 四圈 game is 16 dealer passes.
261
262	### House rules (switches in `Rules`, all on the settings screen)
263
264	- 過水 `sacredDiscard` (on) — pass on a tile you could have won with and it
265	is dead to you until your own next draw; the seat shows a 過水 badge listing
266	what it is locked out of, so the missing 胡 button is never a mystery. A draw
267	from either end of the wall lifts it. `sacredClearedByClaim` (off) decides
268	whether taking a 吃 / 碰 / 槓 lifts it too — tables genuinely differ.
269	- 一炮多響 `multipleWinners` (off) — one discard pays out to every seat that
270	calls on it, each settled separately against the discarder. With it off the
271	tile goes to the caller nearest the discarder. Either way the table now waits
272	for other seats that can win before settling, so the nearest seat wins the
273	tile rather than the quickest hand — and the 摸牌 button still closes the
274	window on anyone dithering.
275	- 包牌 `liability` (on) — feeding the pung that completes a visible 大三元
276	or 大四喜 makes the feeder answer for the whole hand, in place of all three
277	payers. Only the seat that fed the last of those sets is on the hook, and
278	only if it came off a discard: a hand that assembled them itself, or closed
279	the set with a 暗槓, has nobody to blame.
280
281	### 台 scoring (`src/game/tai.ts`)
282
283	自摸 1 · 門清 1 · 門清自摸 +1 · 全求人 2 · 平胡 2 · 五門齊 2 · 正花 1 each ·
284	花槓 2 · 八仙過海 8 · 圈風 / 門風 1 each · 三元牌 1 each · 小三元 4 · 大三元 8 ·
285	小四喜 8 · 大四喜 16 · 碰碰胡 4 · 混一色 4 · 清一色 8 · 字一色 16 ·
286	三暗刻 2 / 四暗刻 5 / 五暗刻 8 · 獨聽 · 單釣 1 · 搶槓 1 · 槓上開花 1 ·
287	海底撈月 1 · 河底撈魚 1 · 天胡 16 · 地胡 16 · 人胡 8 · 莊家 1 (連N拉N → 2N+1)
288
289	Ambiguous hands are decomposed every legal way and scored at the best reading.
290
291	Payment (`Game.settle`): one unit is `底 + 台 × 台值`
292	(`DEFAULT_RULES` = 底 3, 台 1, 100 chips each).
293	放槍一家付 — the discarder alone pays one unit; on 自摸 all three pay one unit
294	each. 拉莊 is billed to the dealer alone when the dealer is a payer, and added
295	to the whole hand when the dealer wins.
296
297	House rules vary a lot; the tai table and payments are plain data/functions in
298	`tai.ts` and `types.ts` if yours differ.
299
300	## The voice pack
301
302	A mahjong table only ever says about fifty things — 42 tile names and a handful
303	of calls — so the whole vocabulary is rendered ahead of time into
304	`public/voice/` (~330 kB of mp3) rather than left to whatever speech synthesis
305	the browser happens to have. On Linux that is usually espeak-ng, which is
306	intelligible but sounds like a modem; and on a machine with no Chinese voice at
307	all the feature would silently do nothing. Shipping the audio makes playback
308	instant, identical everywhere, and lets a call be cut off mid-word when the
309	next one lands, all through the same Web Audio graph as the chimes.
310
311	`scripts/voice.mjs` is the authoring step, not part of `npm run build`. It needs
312	[piper](https://github.com/OHF-Voice/piper1-gpl) and ffmpeg on PATH:
313
314	```
315	node scripts/voice.mjs # → public/voice/*.mp3 + manifest.json
316	PIPER_MODEL=/path/to/voice.onnx node scripts/voice.mjs # a different voice
317	```
318
319	The wording lives in that script, and some of it is deliberately not the bare
320	tile character: 東 alone is a direction where 東風 is the tile, and the dragons
321	are 紅中 / 發財 / 白板 the way they are actually called — which also gives the
322	phonemiser enough context to get the tone right, since 中 on its own is as
323	likely to come out zhòng.
324
325	The clips here were rendered with piper's `zh_CN-huayan-medium`. If you
326	redistribute this app, check that voice's model card in
327	[piper-voices](https://huggingface.co/rhasspy/piper-voices) for the terms
328	attached to it, the same way you would the tile art below — or re-render the
329	pack with a voice whose terms suit you, which is a single command.
330
331	## Tile art
332
333	`public/tiles/tiles.svg` is the postmodern tileset from
334	[gnome-mahjongg](https://gitlab.gnome.org/GNOME/gnome-mahjongg), extracted from
335	the installed binary's GResource — a 43×2 sprite sheet (second row is the
336	highlighted variant, used for a lifted tile). `public/tiles/back.png` is the
337	blank tile from its smooth theme, tinted jade, since a solitaire game has no
338	face-down art of its own.
339
340	That art is GPL-2.0-or-later. Fine for playing at home; if you ever
341	distribute this app, either honour the GPL or swap the two files for art of your
342	own — `SPRITE_COL` in `tiles.ts` is the only mapping that would need updating.
343
344	Known gaps and house rules that aren't implemented yet are listed in
345	[TODO.md](TODO.md).
346
347	## Layout
348
349	```
350	public/tiles/ sprite sheet + tile back
351	src/game/tiles.ts tile codes, wall, shuffle, sprite mapping
352	src/game/hu.ts hand decomposition, 聽 detection, wait shapes
353	src/game/shanten.ts 向聽 / 進張 counting, for the computer players
354	src/game/bot.ts what a computer player discards and claims (pure)
355	src/game/danger.ts reading the table: who looks ready, which tiles are hot
356	src/game/autoplay.ts when it does it, and how long it appears to think
357	src/game/tai.ts 台 scoring
358	src/game/engine.ts state machine: deal, turns, claim resolution, settlement
359	src/game/wall.ts what is left of the square, and what still blocks a throw
360	src/table/physics.ts the discard pool: rectangles with weight, pure and testable
361	src/table/geometry.ts the table measured — colliders, launch points, throw gate
362	src/table/pool.ts game state ⇄ tiles in the middle, by diffing the discards
363	src/ui/ TileView, Hand (drag and throw), Seat, Center, Pool, Help
364	```
365
366	## The tiles in the middle
367
368	The pool is a small rigid-body solver (`src/table/physics.ts`) that knows nothing
369	about mahjong, the DOM, or the clock: fixed 1/120s steps, no randomness of its
370	own, and everything in table pixels. Given the same throws it produces the same
371	pile every time, which is what lets a refresh mid-hand come back to the pile you
372	had rather than a freshly scattered one — positions are derived from the hand
373	number and each tile's place in its thrower's discards, never saved.
374
375	It is drawn on a canvas that spans the whole table, not just the centre.
376	That is deliberate: `.slot` and `.seat` both clip their own contents, which is
377	why a tile can't be animated out of a strip as an element. On the canvas there is
378	nothing to clip it, so a tile lifted out of a hand crosses the table in one
379	piece.
380
381	Nothing about the square is calculated twice. Its size lives entirely in CSS
382	(`--ws`, `--wd`), so `geometry.ts` measures it instead of restating that
383	arithmetic: `WallRing` already renders every stack as a real element tagged with
384	its index, and the colliders are those elements' bounding rects. That one
385	mapping is what makes the wall a physical object — the thing a thrown tile
386	bounces off, and the thing the throw gate casts its ray at.
387
388	## What is left of the wall
389
390	Four walls of eighteen full-size stacks want about 560px a side. No ordinary
391	window has that between the top and bottom strips, and the tile is not allowed
392	to shrink to make it fit — a tile in the wall is the same tile you play with, so
393	drawing it smaller was a visible lie.
394
395	What saves it is that nobody ever sees a whole wall: four hands come off the
396	front before the table is on screen, so barely half of it is left by then. So
397	only the stacks still standing are drawn, and they are laid out around a ring
398	cut to the middle rather than to eighteen — `ringLayout` in `game/wall.ts`
399	measures how many stacks a side can take (`WallRing` renders one hidden cell and
400	asks CSS how big it came out) and shares what is left over the four sides in
401	proportion. Every seat keeps a wall in front of it instead of the remainder
402	piling into one corner, and the order runs all the way round, so the break point
403	is still at the head of it and the 底牌 tail still at the end.
404
405	Shuffling the wall along as it is eaten costs nothing to look at, because every
406	stack shows the same green back — and it is what people do to a half-eaten wall
407	anyway.
408
409	`pool.ts` never listens for events. It diffs the discards against what it is
410	already drawing, keyed by `seat:index` — and those keys never shift, because
411	discards are only ever pushed and a claim only ever pops the one on top. So a
412	key that appeared is a tile to throw in and a key that went is a tile to take
413	off, which makes undo, 下一局, a claim and resuming a saved game all the same
414	code path. The engine has no idea any of it exists, and the save format did not
415	change.