collin/mahjong

323803dcfe47a2223856c392931f347f318bdbb0 / 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 if you are lucky, 是在哈囉 or 你牌品很差欸 if you are not, and
80	never the same line twice running. How hard it got there only decides how
81	loudly. Never your own edge: you cannot be barged by your own discard.
82	- Arranging — drag any tile in your hand to reorder it; 理牌 sorts it back
83	into suit order. Hands are never auto-sorted after the deal, so an arrangement
84	you set up survives draws, claims and kongs.
85	- Rules — the `?` on your nameplate opens a bilingual rules panel anchored to
86	your own edge of the table and rotated to face you.
87	- Claiming — after a discard, every seat that can claim gets 胡 / 槓 / 碰 /
88	吃 / 過 buttons on their own strip, and they resolve by priority (胡 > 槓/碰 >
89	吃; ties go to the player nearest the discarder in turn order).
90	The table never blocks on a claim. The next player gets a 摸牌 button and
91	may draw whenever they like, which shuts the window on anyone who hasn't
92	called — exactly like shouting 碰 before the next player picks up. A claim
93	already declared still stands, so calling in time always wins the tile. If
94	everyone answers first, play advances on its own without the extra tap.
95	The seat that draws next gets no separate 過 button, because for them the two
96	are the same move: picking up is how you decline. Their draw button reads
97	過．摸牌 while they have something they could have called instead. Wanting to
98	decline but leave the window open for everyone else is just waiting, which is
99	what not pressing anything already does.
100	- On your turn — 自摸, 暗槓 and 加槓 appear automatically when legal.
101	加槓 offers everyone else a 搶槓 chance.
102	- Where the buttons go — the strip is built from its edge inwards, so the
103	action bar holds a fixed height whether or not anything is in it. Otherwise
104	the melds above it shuffled along every time you lifted a tile
105	and 打出五萬 appeared, since a button naming a tile stands taller than a bare
106	過. Every button on the bar is given that one height for the same reason.
107	- When a hand ends — a big arrow drops onto the winner's edge of the table.
108	It lives inside their strip, so it turns with the seat and lands on the right
109	person wherever they are sitting, and 一炮多響 lights up every seat that
110	called. A 流局 has no winner to point at, so it turns the hands over instead:
111	who was 聽牌 and the tiles they were waiting on, the same reveal as at a real
112	table.
113	- Undo — a 復原 button in the middle of the table takes back the last
114	action, naming what it will undo (`復原玩家 2 打五萬`). It sits in the
115	centre rather than on a seat because whoever spots the mis-tap should be
116	able to reach it. Twenty actions deep, cleared when the next hand is dealt.
117	Snapshots live outside the saved state, so an undo does not survive a
118	refresh: what you can take back is what happened while everyone was still
119	watching it happen.
120	- Sound — on by default, muted from the 🔊 button in the middle of the
121	table or from settings. A dry clack as a tile goes down, and a distinct
122	two-note chime when a claim window opens, which is how a slow player notices
123	their 碰 is available before the next player draws it shut. Everything is
124	synthesised with a few oscillators (`src/game/sound.ts`) rather than sampled,
125	so there is nothing to load and the cue lands on the same frame as the tile.
126	Browsers refuse to start audio before the page has been clicked, so the first
127	sound anyone hears is the deal — triggered by the button that starts it.
128	- 報牌 (voice) — a second switch under sound calls the game out loud: 碰,
129	吃, 槓, 胡了, 自摸, and the name of every tile as it is discarded — 三條,
130	五萬, 東風. A flower says 補花 and then which one. A new call cuts off one
131	still being spoken; at table pace the newest is the only one that matters.
132	See [the voice pack](#the-voice-pack) for where the audio comes from.
133	- Settings — 設定 from the lobby, or from the game-over panel: player names,
134	底 / 台 / starting chips, the house-rule switches below, and sound. Kept in
135	`localStorage` separately from the save, so they carry over to the next game.
136	Stakes are locked once a game is under way — they'd otherwise rewrite chips
137	already won.
138
139	## On a phone
140
141	The table assumes four people sitting around a screen lying flat, and about
142	770px in both directions before the middle is worth looking at. A phone has
143	neither, so under `(max-height: 620px), (max-width: 820px)` it switches to the
144	compact layout: nothing is rotated, everything reads upright for the one person
145	holding it, the other three seats shrink to cards showing what is public about
146	them, and the depth that frees up goes to your hand, which is allowed to wrap.
147
148	There is no centre square there — the middle collapses to a one-line bar showing
149	what the wall square was telling you anyway — so there is nowhere to throw a tile
150	to. The compact layout therefore keeps a discard row per seat, and discarding
151	is tap-twice or 打出, exactly as it was. The pool and the throw are a full-size
152	feature.
153
154	The breakpoint is written down once, in `COMPACT_QUERY` in `src/ui/compact.ts`,
155	which sets a `compact` class on `<html>` for the CSS to key off.
156
157	## Computer players
158
159	Single player seats you at the bottom and gives seats 1-3 to the computer.
160	Their tiles go face down and their 聽 / 過水 badges come off, since both would
161	give the hand away; everything public — the pool, melds, flowers, chips — stays
162	exactly as it is, and everyone turns their hand over when the hand ends. They
163	throw their tiles in like anyone else, and under the same rule: a computer seat
164	whose wall is open slides them across, and one still walled in lobs them over.
165
166	The engine does not know the bots exist. `AutoPlay` (`src/game/autoplay.ts`)
167	watches the same state the screen does, and when the seat being waited on
168	belongs to the computer it calls the identical method the button would have
169	called — `discard`, `respond`, `declareConcealedKong`. So scoring, sound,
170	saving, 過水 and 包牌 all work without a special case, and a bot cannot make a
171	move a person could not. It never acts for you and never closes your claim
172	window: if the table is waiting on you, it waits.
173
174	How they play (`src/game/bot.ts`) is one idea applied everywhere. A hand is
175	judged at its resting size — the (5 − melds) × 3 + 1 tiles you hold between a
176	discard and your next draw — by its 向聽 first and by its 進張 count second.
177
178	- Discard — try every distinct tile, keep the one that leaves the best
179	resting hand. Ties go to whatever is hardest to build on: a lone honour with
180	most of its copies already gone, before a lone 五萬 that still has neighbours
181	to meet.
182	- 碰 / 吃 — only when the hand that comes out the other side is strictly
183	closer to home. Melding costs concealment and flexibility, so a claim that
184	merely holds the 向聽 steady is declined — which is why the bots pass on
185	pungs that would narrow a two-sided wait to a single tile.
186	- 槓 — judged more kindly: it pays 台 and fetches a replacement, so standing
187	still is good enough.
188	- 胡 — always taken.
189
190	What they watch you do (`src/game/danger.ts`) is the other half. Efficiency
191	alone throws whatever is fastest and pays for it; these bots read the table
192	first, off the face-up table only — discard rows, exposed melds, the 過水 locks
193	the nameplates already show. Two separate questions:
194
195	- How close does each seat look? Turns taken (a hand is usually settled
196	inside ten goes each, long before the wall looks finished, so counting the
197	wall is the wrong clock), melds exposed, and what they have been throwing
198	lately. Nobody discards 五條 out of a hand that still needs shaping — it comes
199	out once the shape is done, so late middle tiles are the tell. A 過水 lock is
200	a confession: to be locked out of a tile you had to have been able to win on
201	it.
202	- How likely is this tile the one they want? An honour can only be caught by
203	a pair or a triplet; a 五萬 sits in the middle of every run through it. A tile
204	they discarded themselves was not their tile when it went down — not proof
205	now, but the best evidence there is. A tile with no copies left unseen cannot
206	be a pair or triplet wait at all. Two melds in one suit means stay out of that
207	suit. And two dragon pungs down means the third dragon is not going anywhere
208	near the table, because 包牌 bills the feeder for the entire hand.
209
210	Whether any of that changes the discard depends on the bot's own hand. At 聽牌
211	it pushes — nothing short of 包牌 is worth breaking a ready hand for. Two or
212	three away with somebody live across the table and it will give up a whole 向聽
213	step to throw something safe, which is what folding is.
214
215	The estimate is checked against ground truth in the tests rather than assumed:
216	over the tiles bots actually considered, the ones the model rated below 0.2 deal
217	in 0% of the time and the ones above 0.8 deal in 10.5%, cleanly monotonic in
218	between. Switching the read on cuts deal-ins by about 13% over a few hundred
219	hands, takes hands from ~30 discards to ~38, and moves the draw rate from
220	almost nothing to about one hand in ten — which is what a table where people
221	stop feeding each other actually looks like.
222
223	What they know is still only what they can see. `unseenFor` counts the four
224	copies of each tile and subtracts the bot's own hand plus every discard and
225	exposed meld on the table. Neither module ever reads an opponent's concealed
226	tiles or looks at the wall.
227
228	There is no difficulty setting, and the reading stops at the discard: claims are
229	still judged purely on speed, and a bot will take a 碰 that walks it into
230	trouble.
231
232	向聽 lives in `src/game/shanten.ts`, apart from `hu.ts`, because the two want
233	different things: the win check has to be exact, and this one has to be fast —
234	it runs a few hundred times for every discard a bot considers. The tests hold
235	them against each other over random hands, since they work in completely
236	different ways and any disagreement is a bug in the fast one.
237
238	Undo behaves differently against the computer: rewinding into the middle of its
239	turn would only hand the move straight back to it, so one press goes back to
240	the last point you had a decision to make, computer replies and all.
241
242	## Saving
243
244	The game state is plain data, so a save is just its JSON in `localStorage`,
245	rewritten after every move. Close the lid, refresh, or run the battery flat and
246	nothing is lost — the lobby offers 繼續對局 Resume above the two ways to
247	start a fresh one, showing whether it was a solo or a hotseat game, the round,
248	hand number, chip counts and when it was saved. Which seats the computer holds
249	is part of the state, so a save resumes as the kind of game it was. A
250	save is validated before it is offered (four players, 144 tiles accounted for),
251	so a truncated or hand-edited one is ignored rather than loaded into a broken
252	table. `VERSION` in `save.ts` retires old saves if the state shape changes.
253
254	## Rules implemented
255
256	- 144 tiles (four of each suit/honour, eight flowers), 16-tile hands, dealer
257	draws the 17th.
258	- 補花 at the deal and on every drawn flower, replacements from the back of the
259	wall.
260	- 吃 only from 上家; 碰/槓/胡 from anyone. 明槓, 暗槓, 加槓, 搶槓, 槓上開花.
261	- 流局 when 16 tiles remain (`Rules.wallReserve`); the dealer keeps the deal on a
262	draw or on a dealer win (連莊), otherwise the deal passes and the round wind
263	advances every four passes. A full 四圈 game is 16 dealer passes.
264
265	### House rules (switches in `Rules`, all on the settings screen)
266
267	- 過水 `sacredDiscard` (on) — pass on a tile you could have won with and it
268	is dead to you until your own next draw; the seat shows a 過水 badge listing
269	what it is locked out of, so the missing 胡 button is never a mystery. A draw
270	from either end of the wall lifts it. `sacredClearedByClaim` (off) decides
271	whether taking a 吃 / 碰 / 槓 lifts it too — tables genuinely differ.
272	- 一炮多響 `multipleWinners` (off) — one discard pays out to every seat that
273	calls on it, each settled separately against the discarder. With it off the
274	tile goes to the caller nearest the discarder. Either way the table now waits
275	for other seats that can win before settling, so the nearest seat wins the
276	tile rather than the quickest hand — and the 摸牌 button still closes the
277	window on anyone dithering.
278	- 包牌 `liability` (on) — feeding the pung that completes a visible 大三元
279	or 大四喜 makes the feeder answer for the whole hand, in place of all three
280	payers. Only the seat that fed the last of those sets is on the hook, and
281	only if it came off a discard: a hand that assembled them itself, or closed
282	the set with a 暗槓, has nobody to blame.
283
284	### 台 scoring (`src/game/tai.ts`)
285
286	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 ·
287	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 ·
288	小四喜 8 · 大四喜 16 · 碰碰胡 4 · 混一色 4 · 清一色 8 · 字一色 16 ·
289	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 ·
290	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)
291
292	Ambiguous hands are decomposed every legal way and scored at the best reading.
293
294	Payment (`Game.settle`): one unit is `底 + 台 × 台值`
295	(`DEFAULT_RULES` = 底 3, 台 1, 100 chips each).
296	放槍一家付 — the discarder alone pays one unit; on 自摸 all three pay one unit
297	each. 拉莊 is billed to the dealer alone when the dealer is a payer, and added
298	to the whole hand when the dealer wins.
299
300	House rules vary a lot; the tai table and payments are plain data/functions in
301	`tai.ts` and `types.ts` if yours differ.
302
303	## The voice pack
304
305	A mahjong table only ever says about fifty things — 42 tile names and a handful
306	of calls — so the whole vocabulary is rendered ahead of time into
307	`public/voice/` (~330 kB of mp3) rather than left to whatever speech synthesis
308	the browser happens to have. On Linux that is usually espeak-ng, which is
309	intelligible but sounds like a modem; and on a machine with no Chinese voice at
310	all the feature would silently do nothing. Shipping the audio makes playback
311	instant, identical everywhere, and lets a call be cut off mid-word when the
312	next one lands, all through the same Web Audio graph as the chimes.
313
314	`scripts/voice.mjs` is the authoring step, not part of `npm run build`. It needs
315	[piper](https://github.com/OHF-Voice/piper1-gpl) and ffmpeg on PATH:
316
317	```
318	node scripts/voice.mjs # → public/voice/*.mp3 + manifest.json
319	PIPER_MODEL=/path/to/voice.onnx node scripts/voice.mjs # a different voice
320	```
321
322	The wording lives in that script, and some of it is deliberately not the bare
323	tile character: 東 alone is a direction where 東風 is the tile, and the dragons
324	are 紅中 / 發財 / 白板 the way they are actually called — which also gives the
325	phonemiser enough context to get the tone right, since 中 on its own is as
326	likely to come out zhòng.
327
328	The clips here were rendered with piper's `zh_CN-huayan-medium`. If you
329	redistribute this app, check that voice's model card in
330	[piper-voices](https://huggingface.co/rhasspy/piper-voices) for the terms
331	attached to it, the same way you would the tile art below — or re-render the
332	pack with a voice whose terms suit you, which is a single command.
333
334	## Tile art
335
336	`public/tiles/tiles.svg` is the postmodern tileset from
337	[gnome-mahjongg](https://gitlab.gnome.org/GNOME/gnome-mahjongg), extracted from
338	the installed binary's GResource — a 43×2 sprite sheet (second row is the
339	highlighted variant, used for a lifted tile). `public/tiles/back.png` is the
340	blank tile from its smooth theme, tinted jade, since a solitaire game has no
341	face-down art of its own.
342
343	That art is GPL-2.0-or-later. Fine for playing at home; if you ever
344	distribute this app, either honour the GPL or swap the two files for art of your
345	own — `SPRITE_COL` in `tiles.ts` is the only mapping that would need updating.
346
347	Known gaps and house rules that aren't implemented yet are listed in
348	[TODO.md](TODO.md).
349
350	## Layout
351
352	```
353	public/tiles/ sprite sheet + tile back
354	src/game/tiles.ts tile codes, wall, shuffle, sprite mapping
355	src/game/hu.ts hand decomposition, 聽 detection, wait shapes
356	src/game/shanten.ts 向聽 / 進張 counting, for the computer players
357	src/game/bot.ts what a computer player discards and claims (pure)
358	src/game/danger.ts reading the table: who looks ready, which tiles are hot
359	src/game/autoplay.ts when it does it, and how long it appears to think
360	src/game/tai.ts 台 scoring
361	src/game/engine.ts state machine: deal, turns, claim resolution, settlement
362	src/game/wall.ts what is left of the square, and what still blocks a throw
363	src/table/physics.ts the discard pool: rectangles with weight, pure and testable
364	src/table/geometry.ts the table measured — colliders, launch points, throw gate
365	src/table/pool.ts game state ⇄ tiles in the middle, by diffing the discards
366	src/ui/ TileView, Hand (drag and throw), Seat, Center, Pool, Help
367	```
368
369	## The tiles in the middle
370
371	The pool is a small rigid-body solver (`src/table/physics.ts`) that knows nothing
372	about mahjong, the DOM, or the clock: fixed 1/120s steps, no randomness of its
373	own, and everything in table pixels. Given the same throws it produces the same
374	pile every time, which is what lets a refresh mid-hand come back to the pile you
375	had rather than a freshly scattered one — positions are derived from the hand
376	number and each tile's place in its thrower's discards, never saved.
377
378	It is drawn on a canvas that spans the whole table, not just the centre.
379	That is deliberate: `.slot` and `.seat` both clip their own contents, which is
380	why a tile can't be animated out of a strip as an element. On the canvas there is
381	nothing to clip it, so a tile lifted out of a hand crosses the table in one
382	piece.
383
384	Nothing about the square is calculated twice. Its size lives entirely in CSS
385	(`--ws`, `--wd`), so `geometry.ts` measures it instead of restating that
386	arithmetic: `WallRing` already renders every stack as a real element tagged with
387	its index, and the colliders are those elements' bounding rects. That one
388	mapping is what makes the wall a physical object — the thing a thrown tile
389	bounces off, and the thing the throw gate casts its ray at.
390
391	## What is left of the wall
392
393	Four walls of eighteen full-size stacks want about 560px a side. No ordinary
394	window has that between the top and bottom strips, and the tile is not allowed
395	to shrink to make it fit — a tile in the wall is the same tile you play with, so
396	drawing it smaller was a visible lie.
397
398	What saves it is that nobody ever sees a whole wall: four hands come off the
399	front before the table is on screen, so barely half of it is left by then. So
400	only the stacks still standing are drawn, and they are laid out around a ring
401	cut to the middle rather than to eighteen — `ringLayout` in `game/wall.ts`
402	measures how many stacks a side can take (`WallRing` renders one hidden cell and
403	asks CSS how big it came out) and shares what is left over the four sides in
404	proportion. Every seat keeps a wall in front of it instead of the remainder
405	piling into one corner, and the order runs all the way round, so the break point
406	is still at the head of it and the 底牌 tail still at the end.
407
408	Shuffling the wall along as it is eaten costs nothing to look at, because every
409	stack shows the same green back — and it is what people do to a half-eaten wall
410	anyway.
411
412	`pool.ts` never listens for events. It diffs the discards against what it is
413	already drawing, keyed by `seat:index` — and those keys never shift, because
414	discards are only ever pushed and a claim only ever pops the one on top. So a
415	key that appeared is a tile to throw in and a key that went is a tile to take
416	off, which makes undo, 下一局, a claim and resuming a saved game all the same
417	code path. The engine has no idea any of it exists, and the save format did not
418	change.