The Wall

Core/Wall.cs manages all the tiles not in players' hands: the live wall, the dead wall (王牌), dora/ura indicators, and the rinshan (replacement) tiles.

Layout

                           ┌─────────── dead wall (王牌) ───────────┐
live wall (draw from here) │  dora indicators │ ura indicators │ rinshan │
◀──────────────────────────┘                                            

Key fields:

Field	Meaning
remaining	The live wall; tiles are drawn from the end.
rinshan	Replacement tiles for kans/nukidora.
doras / uradoras	The dora and ura-dora indicator stacks.
revealedDoraCount / revealedUradoraCount	How many of each are face-up.
initialWall	A flattened, physical 136-tile layout for rendering/replay.
NumRemaining	Live tiles left to draw, accounting for the reserved dead wall.
IsHaitei	NumRemaining <= 0 — the exhaustive-draw boundary.

Constants: NUM_DORA = 5, NUM_RINSHAN = 4.

Lifecycle and draws

• Reset() — called at the start of each hand. It rebuilds the wall from config.initialTiles (each becomes a fresh GameTile with a new trace id), shuffles with the game RNG, then pops the rinshan, dora, and ura stacks and builds initialWall.
• Draw() / Draw(count) — draw from the live wall (source = Wall).
• DrawRinshan() — draw a replacement tile (source = Wanpai).
• RevealDora(isKan) — flip the next dora and/or ura indicator, according to the DoraOption flags in effect (initial vs. kan timing); returns the new indicator.
• CountDora(tile) / CountUradora(tile) — how many han a tile earns from the currently revealed indicators.

The initialWall layout

BuildInitialWall() produces a single flat list in draw order (first tile drawn first), with the dead wall at the tail: the dora/ura indicators interleaved into stacks, followed by the rinshan tiles paired up. This is what clients render in the "initial wall" viewer and what god-view replays carry so the whole wall can be shown.

Replay tip

initialWall is a static per-round snapshot. If you rebuild client state from a mid-round sync, carry the existing initialWall forward — a sync snapshot does not re-send it.

Nukidora and dead-wall sizing

When DoraOption.Nukidora is enabled, each North that can be pulled needs its own replacement tile, so the rinshan is enlarged:

rinshanSize = NUM_RINSHAN + (number of North tiles in config.initialTiles)

This way kans and nukidora share one enlarged dead wall, and each nuki reduces NumRemaining by exactly one. See the Actions & inquiries page for how nuki is offered, and the engine's dev/event-flow.md for the full nukidora event flow.

Scripted manipulation (tests & effects)

For scenario tests and "search-the-wall" style effects, Wall exposes a rich set of manipulation methods: Remove, FindInHidden, Insert/Replace (live wall, first/last), and PlaceDora / PlaceUradora / PlaceRinshan (plus their Replace… variants). These let a test pin exact tiles into the wall or dead wall before or during a game — see Scenario tests.