collin/mahjong

bbdef458b0281651b752400593a3cd48630b0a57 / 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 badly and it ends up in somebody's tiles — the middle stops
76	exactly where their hand starts, so a tile that comes off the pool arrives in
77	their lap, and one that falls short lands out by their seat. Either way their
78	row takes the knock and rocks back, and with 報牌 on they tell you about it
79	(喂，小心點). How hard it got there only decides how loudly. Never your own
80	edge: you cannot be barged by your own discard.
81	- Arranging — drag any tile in your hand to reorder it; 理牌 sorts it back
82	into suit order. Hands are never auto-sorted after the deal, so an arrangement
83	you set up survives draws, claims and kongs.
84	- Rules — the `?` on your nameplate opens a bilingual rules panel anchored to
85	your own edge of the table and rotated to face you.
86	- Claiming — after a discard, every seat that can claim gets 胡 / 槓 / 碰 /
87	吃 / 過 buttons on their own strip, and they resolve by priority (胡 > 槓/碰 >
88	吃; ties go to the player nearest the discarder in turn order).
89	The table never blocks on a claim. The next player gets a 摸牌 button and
90	may draw whenever they like, which shuts the window on anyone who hasn't
91	called — exactly like shouting 碰 before the next player picks up. A claim
92	already declared still stands, so calling in time always wins the tile. If
93	everyone answers first, play advances on its own without the extra tap.
94	The seat that draws next gets no separate 過 button, because for them the two
95	are the same move: picking up is how you decline. Their draw button reads
96	過．摸牌 while they have something they could have called instead. Wanting to
97	decline but leave the window open for everyone else is just waiting, which is
98	what not pressing anything already does.
99	- On your turn — 自摸, 暗槓 and 加槓 appear automatically when legal.
100	加槓 offers everyone else a 搶槓 chance.
101	- Where the buttons go — the strip is built from its edge inwards, so the
102	action bar holds a fixed height whether or not anything is in it. Otherwise
103	the melds above it shuffled along every time you lifted a tile
104	and 打出五萬 appeared, since a button naming a tile stands taller than a bare
105	過. Every button on the bar is given that one height for the same reason.
106	- When a hand ends — a big arrow drops onto the winner's edge of the table.
107	It lives inside their strip, so it turns with the seat and lands on the right
108	person wherever they are sitting, and 一炮多響 lights up every seat that
109	called. A 流局 has no winner to point at, so it turns the hands over instead:
110	who was 聽牌 and the tiles they were waiting on, the same reveal as at a real
111	table.
112	- Undo — a 復原 button in the middle of the table takes back the last
113	action, naming what it will undo (`復原玩家 2 打五萬`). It sits in the
114	centre rather than on a seat because whoever spots the mis-tap should be
115	able to reach it. Twenty actions deep, cleared when the next hand is dealt.
116	Snapshots live outside the saved state, so an undo does not survive a
117	refresh: what you can take back is what happened while everyone was still
118	watching it happen.
119	- Sound — on by default, muted from the 🔊 button in the middle of the
120	table or from settings. A dry clack as a tile goes down, and a distinct
121	two-note chime when a claim window opens, which is how a slow player notices
122	their 碰 is available before the next player draws it shut. Everything is
123	synthesised with a few oscillators (`src/game/sound.ts`) rather than sampled,
124	so there is nothing to load and the cue lands on the same frame as the tile.
125	Browsers refuse to start audio before the page has been clicked, so the first
126	sound anyone hears is the deal — triggered by the button that starts it.
127	- 報牌 (voice) — a second switch under sound calls the game out loud: 碰,
128	吃, 槓, 胡了, 自摸, and the name of every tile as it is discarded — 三條,
129	五萬, 東風. A flower says 補花 and then which one. A new call cuts off one
130	still being spoken; at table pace the newest is the only one that matters.
131	See [the voice pack](#the-voice-pack) for where the audio comes from.
132	- Settings — 設定 from the lobby, or from the game-over panel: player names,
133	底 / 台 / starting chips, the house-rule switches below, and sound. Kept in
134	`localStorage` separately from the save, so they carry over to the next game.
135	Stakes are locked once a game is under way — they'd otherwise rewrite chips
136	already won.
137
138	## On a phone
139
140	The table assumes four people sitting around a screen lying flat, and about
141	770px in both directions before the middle is worth looking at. A phone has
142	neither, so under `(max-height: 620px), (max-width: 820px)` it switches to the
143	compact layout: nothing is rotated, everything reads upright for the one person
144	holding it, the other three seats shrink to cards showing what is public about
145	them, and the depth that frees up goes to your hand, which is allowed to wrap.
146
147	There is no centre square there — the middle collapses to a one-line bar showing
148	what the wall square was telling you anyway — so there is nowhere to throw a tile
149	to. The compact layout therefore keeps a discard row per seat, and discarding
150	is tap-twice or 打出, exactly as it was. The pool and the throw are a full-size
151	feature.
152
153	The breakpoint is written down once, in `COMPACT_QUERY` in `src/ui/compact.ts`,
154	which sets a `compact` class on `<html>` for the CSS to key off.
155
156	## Computer players
157
158	Single player seats you at the bottom and gives seats 1-3 to the computer.
159	Their tiles go face down and their 聽 / 過水 badges come off, since both would
160	give the hand away; everything public — the pool, melds, flowers, chips — stays
161	exactly as it is, and everyone turns their hand over when the hand ends. They
162	throw their tiles in like anyone else, and under the same rule: a computer seat
163	whose wall is open slides them across, and one still walled in lobs them over.
164
165	The engine does not know the bots exist. `AutoPlay` (`src/game/autoplay.ts`)
166	watches the same state the screen does, and when the seat being waited on
167	belongs to the computer it calls the identical method the button would have
168	called — `discard`, `respond`, `declareConcealedKong`. So scoring, sound,
169	saving, 過水 and 包牌 all work without a special case, and a bot cannot make a
170	move a person could not. It never acts for you and never closes your claim
171	window: if the table is waiting on you, it waits.
172
173	How they play (`src/game/bot.ts`) is one idea applied everywhere. A hand is
174	judged at its resting size — the (5 − melds) × 3 + 1 tiles you hold between a
175	discard and your next draw — by its 向聽 first and by its 進張 count second.
176
177	- Discard — try every distinct tile, keep the one that leaves the best
178	resting hand. Ties go to whatever is hardest to build on: a lone honour with
179	most of its copies already gone, before a lone 五萬 that still has neighbours
180	to meet.
181	- 碰 / 吃 — only when the hand that comes out the other side is strictly
182	closer to home. Melding costs concealment and flexibility, so a claim that
183	merely holds the 向聽 steady is declined — which is why the bots pass on
184	pungs that would narrow a two-sided wait to a single tile.
185	- 槓 — judged more kindly: it pays 台 and fetches a replacement, so standing
186	still is good enough.
187	- 胡 — always taken.
188
189	What they watch you do (`src/game/danger.ts`) is the other half. Efficiency
190	alone throws whatever is fastest and pays for it; these bots read the table
191	first, off the face-up table only — discard rows, exposed melds, the 過水 locks
192	the nameplates already show. Two separate questions:
193
194	- How close does each seat look? Turns taken (a hand is usually settled
195	inside ten goes each, long before the wall looks finished, so counting the
196	wall is the wrong clock), melds exposed, and what they have been throwing
197	lately. Nobody discards 五條 out of a hand that still needs shaping — it comes
198	out once the shape is done, so late middle tiles are the tell. A 過水 lock is
199	a confession: to be locked out of a tile you had to have been able to win on
200	it.
201	- How likely is this tile the one they want? An honour can only be caught by
202	a pair or a triplet; a 五萬 sits in the middle of every run through it. A tile
203	they discarded themselves was not their tile when it went down — not proof
204	now, but the best evidence there is. A tile with no copies left unseen cannot
205	be a pair or triplet wait at all. Two melds in one suit means stay out of that
206	suit. And two dragon pungs down means the third dragon is not going anywhere
207	near the table, because 包牌 bills the feeder for the entire hand.
208
209	Whether any of that changes the discard depends on the bot's own hand. At 聽牌
210	it pushes — nothing short of 包牌 is worth breaking a ready hand for. Two or
211	three away with somebody live across the table and it will give up a whole 向聽
212	step to throw something safe, which is what folding is.
213
214	The estimate is checked against ground truth in the tests rather than assumed:
215	over the tiles bots actually considered, the ones the model rated below 0.2 deal
216	in 0% of the time and the ones above 0.8 deal in 10.5%, cleanly monotonic in
217	between. Switching the read on cuts deal-ins by about 13% over a few hundred
218	hands, takes hands from ~30 discards to ~38, and moves the draw rate from
219	almost nothing to about one hand in ten — which is what a table where people
220	stop feeding each other actually looks like.
221
222	What they know is still only what they can see. `unseenFor` counts the four
223	copies of each tile and subtracts the bot's own hand plus every discard and
224	exposed meld on the table. Neither module ever reads an opponent's concealed
225	tiles or looks at the wall.
226
227	There is no difficulty setting, and the reading stops at the discard: claims are
228	still judged purely on speed, and a bot will take a 碰 that walks it into
229	trouble.
230
231	向聽 lives in `src/game/shanten.ts`, apart from `hu.ts`, because the two want
232	different things: the win check has to be exact, and this one has to be fast —
233	it runs a few hundred times for every discard a bot considers. The tests hold
234	them against each other over random hands, since they work in completely
235	different ways and any disagreement is a bug in the fast one.
236
237	Undo behaves differently against the computer: rewinding into the middle of its
238	turn would only hand the move straight back to it, so one press goes back to
239	the last point you had a decision to make, computer replies and all.
240
241	## Saving
242
243	The game state is plain data, so a save is just its JSON in `localStorage`,
244	rewritten after every move. Close the lid, refresh, or run the battery flat and
245	nothing is lost — the lobby offers 繼續對局 Resume above the two ways to
246	start a fresh one, showing whether it was a solo or a hotseat game, the round,
247	hand number, chip counts and when it was saved. Which seats the computer holds
248	is part of the state, so a save resumes as the kind of game it was. A
249	save is validated before it is offered (four players, 144 tiles accounted for),
250	so a truncated or hand-edited one is ignored rather than loaded into a broken
251	table. `VERSION` in `save.ts` retires old saves if the state shape changes.
252
253	## Rules implemented
254
255	- 144 tiles (four of each suit/honour, eight flowers), 16-tile hands, dealer
256	draws the 17th.
257	- 補花 at the deal and on every drawn flower, replacements from the back of the
258	wall.
259	- 吃 only from 上家; 碰/槓/胡 from anyone. 明槓, 暗槓, 加槓, 搶槓, 槓上開花.
260	- 流局 when 16 tiles remain (`Rules.wallReserve`); the dealer keeps the deal on a
261	draw or on a dealer win (連莊), otherwise the deal passes and the round wind
262	advances every four passes. A full 四圈 game is 16 dealer passes.
263
264	### House rules (switches in `Rules`, all on the settings screen)
265
266	- 過水 `sacredDiscard` (on) — pass on a tile you could have won with and it
267	is dead to you until your own next draw; the seat shows a 過水 badge listing
268	what it is locked out of, so the missing 胡 button is never a mystery. A draw
269	from either end of the wall lifts it. `sacredClearedByClaim` (off) decides
270	whether taking a 吃 / 碰 / 槓 lifts it too — tables genuinely differ.
271	- 一炮多響 `multipleWinners` (off) — one discard pays out to every seat that
272	calls on it, each settled separately against the discarder. With it off the
273	tile goes to the caller nearest the discarder. Either way the table now waits
274	for other seats that can win before settling, so the nearest seat wins the
275	tile rather than the quickest hand — and the 摸牌 button still closes the
276	window on anyone dithering.
277	- 包牌 `liability` (on) — feeding the pung that completes a visible 大三元
278	or 大四喜 makes the feeder answer for the whole hand, in place of all three
279	payers. Only the seat that fed the last of those sets is on the hook, and
280	only if it came off a discard: a hand that assembled them itself, or closed
281	the set with a 暗槓, has nobody to blame.
282
283	### 台 scoring (`src/game/tai.ts`)
284
285	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 ·
286	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 ·
287	小四喜 8 · 大四喜 16 · 碰碰胡 4 · 混一色 4 · 清一色 8 · 字一色 16 ·
288	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 ·
289	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)
290
291	Ambiguous hands are decomposed every legal way and scored at the best reading.
292
293	Payment (`Game.settle`): one unit is `底 + 台 × 台值`
294	(`DEFAULT_RULES` = 底 3, 台 1, 100 chips each).
295	放槍一家付 — the discarder alone pays one unit; on 自摸 all three pay one unit
296	each. 拉莊 is billed to the dealer alone when the dealer is a payer, and added
297	to the whole hand when the dealer wins.
298
299	House rules vary a lot; the tai table and payments are plain data/functions in
300	`tai.ts` and `types.ts` if yours differ.
301
302	## The voice pack
303
304	A mahjong table only ever says about fifty things — 42 tile names and a handful
305	of calls — so the whole vocabulary is rendered ahead of time into
306	`public/voice/` (~330 kB of mp3) rather than left to whatever speech synthesis
307	the browser happens to have. On Linux that is usually espeak-ng, which is
308	intelligible but sounds like a modem; and on a machine with no Chinese voice at
309	all the feature would silently do nothing. Shipping the audio makes playback
310	instant, identical everywhere, and lets a call be cut off mid-word when the
311	next one lands, all through the same Web Audio graph as the chimes.
312
313	`scripts/voice.mjs` is the authoring step, not part of `npm run build`. It needs
314	[piper](https://github.com/OHF-Voice/piper1-gpl) and ffmpeg on PATH:
315
316	```
317	node scripts/voice.mjs # → public/voice/*.mp3 + manifest.json
318	PIPER_MODEL=/path/to/voice.onnx node scripts/voice.mjs # a different voice
319	```
320
321	The wording lives in that script, and some of it is deliberately not the bare
322	tile character: 東 alone is a direction where 東風 is the tile, and the dragons
323	are 紅中 / 發財 / 白板 the way they are actually called — which also gives the
324	phonemiser enough context to get the tone right, since 中 on its own is as
325	likely to come out zhòng.
326
327	The clips here were rendered with piper's `zh_CN-huayan-medium`. If you
328	redistribute this app, check that voice's model card in
329	[piper-voices](https://huggingface.co/rhasspy/piper-voices) for the terms
330	attached to it, the same way you would the tile art below — or re-render the
331	pack with a voice whose terms suit you, which is a single command.
332
333	## Tile art
334
335	`public/tiles/tiles.svg` is the postmodern tileset from
336	[gnome-mahjongg](https://gitlab.gnome.org/GNOME/gnome-mahjongg), extracted from
337	the installed binary's GResource — a 43×2 sprite sheet (second row is the
338	highlighted variant, used for a lifted tile). `public/tiles/back.png` is the
339	blank tile from its smooth theme, tinted jade, since a solitaire game has no
340	face-down art of its own.
341
342	That art is GPL-2.0-or-later. Fine for playing at home; if you ever
343	distribute this app, either honour the GPL or swap the two files for art of your
344	own — `SPRITE_COL` in `tiles.ts` is the only mapping that would need updating.
345
346	Known gaps and house rules that aren't implemented yet are listed in
347	[TODO.md](TODO.md).
348
349	## Layout
350
351	```
352	public/tiles/ sprite sheet + tile back
353	src/game/tiles.ts tile codes, wall, shuffle, sprite mapping
354	src/game/hu.ts hand decomposition, 聽 detection, wait shapes
355	src/game/shanten.ts 向聽 / 進張 counting, for the computer players
356	src/game/bot.ts what a computer player discards and claims (pure)
357	src/game/danger.ts reading the table: who looks ready, which tiles are hot
358	src/game/autoplay.ts when it does it, and how long it appears to think
359	src/game/tai.ts 台 scoring
360	src/game/engine.ts state machine: deal, turns, claim resolution, settlement
361	src/game/wall.ts what is left of the square, and what still blocks a throw
362	src/table/physics.ts the discard pool: rectangles with weight, pure and testable
363	src/table/geometry.ts the table measured — colliders, launch points, throw gate
364	src/table/pool.ts game state ⇄ tiles in the middle, by diffing the discards
365	src/ui/ TileView, Hand (drag and throw), Seat, Center, Pool, Help
366	```
367
368	## The tiles in the middle
369
370	The pool is a small rigid-body solver (`src/table/physics.ts`) that knows nothing
371	about mahjong, the DOM, or the clock: fixed 1/120s steps, no randomness of its
372	own, and everything in table pixels. Given the same throws it produces the same
373	pile every time, which is what lets a refresh mid-hand come back to the pile you
374	had rather than a freshly scattered one — positions are derived from the hand
375	number and each tile's place in its thrower's discards, never saved.
376
377	It is drawn on a canvas that spans the whole table, not just the centre.
378	That is deliberate: `.slot` and `.seat` both clip their own contents, which is
379	why a tile can't be animated out of a strip as an element. On the canvas there is
380	nothing to clip it, so a tile lifted out of a hand crosses the table in one
381	piece.
382
383	Nothing about the square is calculated twice. Its size lives entirely in CSS
384	(`--ws`, `--wd`), so `geometry.ts` measures it instead of restating that
385	arithmetic: `WallRing` already renders every stack as a real element tagged with
386	its index, and the colliders are those elements' bounding rects. That one
387	mapping is what makes the wall a physical object — the thing a thrown tile
388	bounces off, and the thing the throw gate casts its ray at.
389
390	## What is left of the wall
391
392	Four walls of eighteen full-size stacks want about 560px a side. No ordinary
393	window has that between the top and bottom strips, and the tile is not allowed
394	to shrink to make it fit — a tile in the wall is the same tile you play with, so
395	drawing it smaller was a visible lie.
396
397	What saves it is that nobody ever sees a whole wall: four hands come off the
398	front before the table is on screen, so barely half of it is left by then. So
399	only the stacks still standing are drawn, and they are laid out around a ring
400	cut to the middle rather than to eighteen — `ringLayout` in `game/wall.ts`
401	measures how many stacks a side can take (`WallRing` renders one hidden cell and
402	asks CSS how big it came out) and shares what is left over the four sides in
403	proportion. Every seat keeps a wall in front of it instead of the remainder
404	piling into one corner, and the order runs all the way round, so the break point
405	is still at the head of it and the 底牌 tail still at the end.
406
407	Shuffling the wall along as it is eaten costs nothing to look at, because every
408	stack shows the same green back — and it is what people do to a half-eaten wall
409	anyway.
410
411	`pool.ts` never listens for events. It diffs the discards against what it is
412	already drawing, keyed by `seat:index` — and those keys never shift, because
413	discards are only ever pushed and a claim only ever pops the one on top. So a
414	key that appeared is a tile to throw in and a key that went is a tile to take
415	off, which makes undo, 下一局, a claim and resuming a saved game all the same
416	code path. The engine has no idea any of it exists, and the save format did not
417	change.