undercooked/README.md

# Undercooked

A cooperative, **in-browser**, Overcooked-style kitchen game: 1–4 players share one
kitchen over WebSockets, cook orders against the clock, and climb a campaign of
levels that get progressively harder. Lobbies are **anonymous** — no accounts, no
email, no password: you create a room, share the 5-character code, play.

> Working title. "Overcooked" is a trademark of Ghost Town Games/Studio MDG; this
> project is an independent homage with its own art, code, and content.

## Status

Phases **01** (runnable service scaffold), **02** (level content, schema and
validation), **03** (the deterministic simulation kernel: fixed-step tick,
movement and collision, the action button, the hands, the replay goldens),
**04** (the kitchen pipeline: station state machines, the ticket rail,
serve scoring, freshness and the dirty loop, the round verdict with stars)
and **05** (anonymous lobbies and room lifecycle: the `RoomSupervisor`,
the guarded `Room` FSM, the in-memory session store, the lifecycle
integration suite), **06** (the realtime WebSocket protocol: the
`/ws/{code}` transport, the versioned JSON wire contract with inbound
guardrails, input ingestion with sequence discipline, the quantized
snapshot stream, heartbeats and seat grace — `docs/PROTOCOL.md`) and
**07** (the canvas client, art and HUD: the in-repo SVG atlas, the
screen state machine, the snapshot buffer with 100 ms interpolation,
the DPR-aware Canvas renderer, the DOM HUD and the desktop keyboard
input — `docs/CLIENT.md`) are **complete**; the next pending phase is
`08_client_prediction_and_touch`. What runs today:

- **The service.** The Python toolchain is locked (`uv.lock`), configuration is a
  single typed, validated `Settings` object (`DEBUGPY` support included), and
  `uv run undercooked` starts a FastAPI server that serves the client shell at `/`,
  the browser assets from `app/static/`, and `GET /healthz` — which answers
  `{"status":"ok","version":"0.1.0","rooms":<live room count>}` from the room
  supervisor (phase 05) — with the security headers (CSP `default-src 'self'`) on
  every response.
- **The content.** The recipe book and the first two campaign levels live in
  `levels/`; `sim/level.py` parses them into typed models, `sim/validation.py` runs
  PLAN §8's named rules, and `create_app` loads + validates that bundle at startup and
  **refuses to boot** broken content — the named-rule report goes to stderr and
  `undercooked` exits `2` instead of serving a half-working kitchen. `GET /api/levels`,
  `GET /api/levels/{id}` and `GET /api/config` answer from it, and
  `undercooked-levels` gives authors the same gate from the command line
  (`docs/LEVELS.md` is the schema reference).
- **The tick.** `sim/state_build.py` builds a round from level + seats + seed and
  `sim/step.py` advances it in whole `0.05` s substeps (20 Hz, A4) with a splitmix64 RNG
  seeded from the round seed — pure (no clock, no `random`, nothing mutated), replayable
  from a seed plus an input script, and 100 % covered. The clock, the input contract and
  the round's end condition are real. `docs/SIMULATION.md`
  is the contract, `tests/sim/test_rng.py` locks the generator's published vectors.
- **Walking the kitchen.** `sim/movement.py` + `sim/collision.py` are stage 3 of the tick:
  intent is clamped server-side (`move=(50,0)` walks at 3.5 tiles/s, not 175), accelerated
  at 30 tiles/s² and integrated one axis at a time against an axis-aligned sweep, so a cook
  stops flush against a wall instead of inside it, slides along it for free, cannot tunnel a
  1-tile wall even at the coarsest legal `dt`, and cannot clip a diagonal corner. Walls,
  counters, void, off-map and the solid fixtures (`spawn_shelf`, `chop_board`, `stove`,
  `prep`) block; `serve`, `sink` and `trash` do not. Cooks soft-push each other apart
  symmetrically and positionally — a bump never injects velocity — and only a genuine
  terrain deadlock drops an input, the later-received one, exactly like the kernel's
  arbitration. Stun (`0.6` s) pins velocity and position and reports one `stunned` event on
  entry; facing follows the last non-zero intent, so an action press while standing still
  does not spin the cook. Proven by hand-computed geometry in `tests/sim/test_movement.py`,
  by a 2000-substep four-cook random walk from the sim's own RNG that re-checks containment,
  non-overlap and hash equality after *every* substep
  (`tests/sim/test_movement_stress.py`), and by the same walk on the shipped levels through
  the whole `step()` (`tests/sim/test_movement_kernel.py`).
- **The action button.** `sim/interact.py` is the second half of stage 2 of the tick:
  the one `action` flag per frame becomes one press per rising edge, so however long the
  button is held there is one effect — and one named refusal when there is nothing to do
  (`DENIED` with `out_of_reach`, `hands_full`, `station_busy`, `contested_lost`, … in the
  payload, which the client turns into a nudge; a silent no-op is the failure mode PLAN §5
  bans by name). A press resolves a reach zone — the tile in front, then the two
  diagonal-front tiles (a 0.6-tile forgiveness beyond the 1-tile reach), then the tile
  underfoot — and a ladder picks the verb: a full hand sets its item down on the fixture
  (the spawn shelf is the escape hatch), a free hand picks from a ready fixture or shelf
  stock, a stunned cook is refused before the target is even read, and a fixture owns
  what is on it (an onion on a chop board is *to be chopped*, not grabbable). Two cooks
  pressing the same item in the same substep are arbitrated by arrival, `seq`, then seat
  index — the loser is told `contested_lost`, never left wondering. The work verbs (chop,
  cook, plate, wash) are spent by `sim/stations.py` (phase 04 task 01's pipeline —
  a set-down on a work surface starts the work, a release freezes the progress, a
  dirty fixture is washed in place); `SERVE` is spent by `sim/scoring.py`
  (phase 04 task 03 — see "Serve scoring" below).
  The long-press trash is real — see "The hands" below; `docs/SIMULATION.md`
  §"The action button" and §"The station pipeline" are the contract. Proven by
  `tests/sim/test_targeting.py` (hand-computed reach geometry, the press edge through the
  whole `step()`) and `tests/sim/test_verbs.py` (a table that covers every `Verb` and every
  `DeniedReason`, plus the gate's contested arbitration).
- **The hands.** `sim/carry.py` is what the verbs *do*: one carried item per cook (a
  second pick is `hands_full`), no floor drops in v1 (a press at open floor is the named
  `nothing_here`), and a set-down is a *placed object* — `RELEASE` / `PLACE_ON_STATION` /
  `PLATE_DISH` put the item on the fixture and stamp it with a mark, so a teammate's pick
  of a set-down within 20 ticks is a `HANDED_OFF` with both ids (the sanctioned pass) and
  an unmarked pipeline input stays the work press's. The trash is long-press and always
  available: holding the button over the can for 8 substeps destroys the carried item
  (`TRASHED`, the raw `−2` score nudge in the payload for phase 04's clamped scoring,
  `counters["trashed"]` up by one); a short press and a walk-away do nothing. A 100-tick
  fuzz of random simultaneous presses re-checks the conservation law
  (`hands + stations + trashed == initial`) after every tick, and a scripted two-player
  pass-and-contest reaches its committed golden hash. `docs/SIMULATION.md` §"The hand" is
  the contract (phase 09's co-op E2E asserts exactly this tie-break). Proven by
  `tests/sim/test_carry.py` and `tests/sim/test_replay_carry.py`.
- **The ticket rail.** `sim/orders.py` is stage 5 of the tick: the level's `orders`
  spec is copied onto the state in tick units at round build (a replay stays
  self-contained), the first order arrives 1.5 s in, the recipe is a seeded draw from
  the level's pool (the order's value is the recipe's `base_score`), the concurrency
  cap holds, a due tick a full rail cannot serve retries 1 s later *without consuming
  the interval draw* (a full rail would otherwise silently warp the spawn cadence),
  and an order's clock — derived, never accumulated — expires on exactly the tick it
  reaches 0: removed, `counters["missed"]` up by one, one `ORDER_MISSED` naming the id
  and recipe (the penalty score deduction and the streak reset are task 03's
  scoring, the single owner of score and streak, injected as the stage's
  `on_miss` callback). Proven by 200 simulated seconds of
  interval bounds and cap under idle and busy rails, same-seed/different-seed
  reproducibility, and twenty randomized spec fuzz runs
  (`tests/sim/test_orders.py`, `tests/sim/test_orders_fuzz.py`); the contract is
  `docs/SIMULATION.md` §"Orders — the ticket rail".
- **Serve scoring.** `sim/scoring.py` is the single owner of the round's
  `score` and `streak`, from both sides: a `SERVE` press at the window
  validates the carried dish (burnt → `burnt`, not a plated dish →
  `no_target`, an ingredient the declared recipe does not require →
  `incomplete`, no live order for the recipe → `wrong_recipe`, an empty
  rail → `no_orders` — each a named `DENIED` with the dish left in the
  hand), and a matched dish is scored `round(base × quality ×
  streak_mult × time_bonus)` — the streak counted *after* the increment and
  capped at `1.5`, the bonus 1.5 with the full deadline unspent down to 1.0
  at the edge — with the order off the rail and the cook's `score`/
  `dishes_served` credited (per-player contribution, display only; a prop
  is dirty from its *use* — the station pipeline's stock bookkeeping —
  not from the serve). A deadline's expiry is the scoring half of the
  rail's miss: `score − order_penalty` floored at 0 and the streak reset,
  injected into `step_orders` as the `on_miss` callback so `orders.py` and
  `scoring.py` never import each other. Pinned by five hand-computed
  serves, the rejection paths, FIFO and the caps
  (`tests/sim/test_scoring.py`) and 500 seeded random serves
  (`tests/sim/test_scoring_property.py`); the contract is
  `docs/SIMULATION.md` §"Serve scoring".
- **Freshness — the clocks that create pressure.** `sim/freshness.py`
  runs as substep stage 4b (after the station pipelines, before the
  orders) and decays the quality: a dish on a ready stove burns exactly
  `BURN_AFTER_S` (8.0 s) after the ready flip — tick-exact, the 160th
  substep — with the station going `DIRTY` (the burnt pot is stuck) and
  one `BURNT` event; a raw or chopped item left on a board rots linearly
  over `ROT_S` (20.0 s); a carried prepared item decays at half the
  board's rate (a hand is not a fridge); a new raw set-down on a board
  that holds a burnt item destroys it (a named `WASTED`,
  `counters["wasted"]`) while a usable raw item is never silently
  overwritten (the named `station_busy`); a burnt dish is refused by the
  serve window, never scored. The dirty loop's stock — a use moves a prop
  `…_clean → …_dirty`, a wash (the sink, or the in-place wash of a stuck
  prop) moves it back — holds `…_clean + …_dirty == the level's limit`
  every tick, and the no-dead-end guarantee (a worst-case cook who serves
  everything and never washes until forced never gets stuck: one wash
  restores the stock) is proven on a 2 000-tick run
  (`tests/sim/test_freshness.py`, `tests/sim/test_no_deadlock.py`); the
  contract is `docs/SIMULATION.md` §"Freshness".
- **Round end — the verdict, the settle, the stars.** `sim/round_state.py`
  runs as substep stage 7 and owns the round's clock and its verdict (which
  turns on `score` against `target_score` and nothing else): the round wins
  the moment the score reaches the target (the clock holds at that
  substep's countdown), or on the buzzer — `WON` if the score made it,
  `LOST` if it did not — with exactly one `ROUND_END` event. A decided
  round then **settles**: for `SETTLE_S` (1.0 s, the room's, phase 05), the
  kernel freezes every gameplay stage — inputs ignored, no movement,
  stations, freshness, orders or hazards — and only the frozen clock and
  the tick keep running, so the verdict substep's events land and the
  result is a function of the state at the verdict alone. `stars(state)`
  grades a win from the frozen clock — 0 when lost, 1 for winning, 2 with
  ≥ 25 % of the clock left, 3 with ≥ 50 % — and
  `result_payload(state)` is the plain-JSON body of the `round` message the
  protocol phase sends (PLAN §7): `result`, `score`, `target`, `stars`,
  `time_left`, the `served`/`missed`/`wasted` counters, `longest_streak`
  (owned by `sim/scoring.py`: a serve raises the mark, a miss never resets
  it) and the per-seat `players[]` (`id`, `name`, `score`,
  `dishes_served`, `missed_contrib` — the round's missed count spread
  evenly, a display-only estimate: the sim does not attribute an expired
  order to a cook). Pinned by `tests/sim/test_round_state.py` (verdict on
  both sides of the epsilon, the settle freeze, the star boundaries one
  tick below and exactly at 25 %/50 %, the `ABORTED` seam, the
  `longest_streak` owner/reader) and `tests/sim/test_result_payload.py`
  (a recursive JSON-safety walk with zero leaks, the exact key sets,
  byte-stability across two identical runs and across the settle window);
  the contract is `docs/SIMULATION.md` §"Round end — the verdict, the
  settle, the stars".
- **The room supervisor (phase 05).** The server-side lobby shell is
  live: `server/rooms.py` mints 5-character Crockford base32 codes (collision-
  checked, never reused), enforces `max_rooms` / `max_players` capacity, keeps a
  one-token-one-room index (a token joining a second room is evicted from the
  first; a *disconnected* seat is kept for the rejoin path), and runs the 5 s GC
  (empty rooms past a 30 s grace, idle lobbies past `lobby_idle_timeout_s`, stale
  tokens). Everything runs on an injected clock (`server/clock.py`), so the tests
  drive the garbage collector with a `FakeClock` and never sleep. The lifecycle is
  testable over HTTP, and it now also rides the phase-06 WebSocket
  transport (`/ws/{code}`; below):
  `POST /api/rooms` (201, the session from the `X-Undercooked-Token`
  header or the body's `token` — or a server-minted token, returned
  once),
  `GET /api/rooms/{code}`, `POST /api/rooms/{code}/join` and
  `GET /api/session` — seats never leak
  other players' tokens, a malformed code 404s exactly like an unknown one
  (US-02 criterion 4), and a full room or a full process is a 503
  `{"code": "room_full"}` (US-01 criterion 7). The `Room` itself is the guarded
  FSM behind those routes — five states, a table of fourteen legal
  transitions, one 20 Hz deadline-scheduled tick task per room and crash
  isolation that closes only the room that crashed (contract: `docs/ROOMS.md`),
  and the ready-up/host flow rides on it. The in-memory **session store**
  (`server/sessions.py`) is live on top: per token it remembers the campaign
  progression — `unlocked_level` (a `WON` round raises it to `order + 1`,
  never decreases it), `best[level_id]` (a `BestRun` of `score`/`stars`/
  `completed_at`, replaced only when the score is higher), the
  `rounds_played` / `dishes_served` counters — LRU-capped at 10 000 (evicting
  the stalest, never the session being created) and wiped on restart (A6);
  `Room.set_level` asks the store's `is_unlocked`, `round_over` records the
  result into every seated player's session, and `GET /api/session` answers
  `to_public` (a fresh token reads `unlocked: 1` with an empty `best`; 400
  `no_token` without the header) (contract: `docs/ROOMS.md` "Progression").
  The **lifecycle integration suite** (phase 05 task 05) drives the whole
  lifecycle over HTTP plus direct `tick_once`: create → 3 joins → ready-up
  → the host's start → the countdown → a scripted full-pipeline `WON` → the
  `ROUND_END` payload → `next_level` → back to `LOBBY` with the same seats
  and colours; plus a solo win with the unlock advanced, the 5th join's and
  the process-capacity 503 `room_full`, malformed ≡ unknown codes (US-02
  criterion 4), the seat-grace and lobby-idle expiries through the GC, and
  one room's crash closing only itself (the test-only `_test_step_override`
  seam on `Room`; contract: `docs/ROOMS.md` "Failure and expiry" and
  "The lifecycle walkthrough").
- **The WebSocket transport (phase 06, task 02).** The room core is on
  the wire: `GET /api/stats` answers the ops census (`rooms` / `players`
  — the occupied seats / `sockets` — live WebSocket connections /
  `tick_hz`), and `WS /ws/{code}` is the game socket — an origin check
  *before* the accept (a disallowed `Origin` is an HTTP `403`, never a
  close frame that looks like a network error), a `hello` within
  `hello_timeout_s` (else close `4400`), a `p` gate (`protocol_mismatch`
  + `4400` before any seat is taken), the supervisor's seat/spectate
  (`room_gone` + `4401` for an unknown code, `room_full` + `4402` for a
  fresh token on a full room), the `welcome` + the current `lobby`, and
  the two per-connection tasks (a non-blocking `pump_out` over a capped
  send queue — the *oldest snapshot* drops first, `lobby` / `round` /
  `err` never — and the `read_in` guardrails: the `max_message_bytes`
  cap → `too_big`, the `max_inputs_per_s` token bucket →
  `rate_limited`, the shape check, the per-state whitelist →
  `wrong_state`; 3 consecutive rate/oversize violations or 5 shape
  violations close `4404`). One socket per token: a second `hello` with
  the same token evicts the first (`evicted` + `4403`, marked dead
  before the close so no ghost frames) — and an evicted socket never
  marks the seat disconnected, so the crown stays put. A *genuine*
  disconnect reaches the room exactly once (`mark_disconnected`),
  releases the registry slot, and leaves no error in the log — an
  abrupt transport close (no close handshake) included. The contract in
  prose is `docs/PROTOCOL.md` (message tables kept equal to the models
  by `tests/unit/test_protocol_doc_sync.py`, close/error codes, the
  limits, and a manual probe that reproduces the handshake without a
  browser); the guardrails are driven by real sockets in
  `tests/integration/test_ws_handshake.py` and the queue policy by
  `tests/unit/test_send_queue_policy.py`.
- **Input ingestion (phase 06, task 03).** The `input` message is on the
  wire: the `seq` discipline (equal → dropped as an idempotent resend,
  backwards → `err` + a `resync` event the client hard-snapshots to,
  gaps ≤ 3 tolerated UDP-style, larger gaps accepted and counted in the
  room stats), the anti-cheat clamp (`move` clamped to unit length and
  quantized to 3 decimals server-side — a client sending `(1000, 1000)`
  walks at `MAX_SPEED` like everyone else, and the position never
  arrives because the message has no position field and `extra="forbid"`
  rejects one), `face` derived from `move` when absent, `act` coerced,
  and `received_at_tick` stamped by the server, never the client. The
  room's per-tick input queue caps at `4 x len(seats)` (overflow drops
  the sender's oldest frame, `inputs_dropped` bumped), a `DISCONNECTED`
  seat's frames are silently ignored, a spectator's get `not_seated`,
  and `Room.stats()` carries the input counters. A wall-clock tick too
  short to fill one substep keeps the queue, so a frame is never
  dropped without being applied. The rules are in `docs/PROTOCOL.md`
  ("Input rules") and driven by real sockets in
  `tests/integration/test_ws_input.py` (the hostile-move bound included).
- **The snapshot stream (phase 06, task 04).** `PLAYING` now broadcasts:
  quantized snapshots (an explicit field map — no `pickle`/`asdict`; the
  grid, station ids, spawn coordinates and the round seed never leave
  the server) at `SNAPSHOT_HZ` for players and half that for
  spectators, encoded once per (frame, audience) and fanned out across
  every connection of it. The stream runs in delta mode (only the
  changed entities, plus a `gone` tombstone for each vanished one; a
  typical idle-kitchen delta is ≥ 40% smaller than a full), with a
  full frame on a fresh connection's first frame, on a dropped
  snapshot's next frame, and on the full cadence (every 20 encoded
  frames), so a client can always resync cheaply. The boundary's
  events ride the frame (the stable `k` names, an explicit short-key
  payload map, capped at 24 per frame with `events_dropped` on
  overflow); outside `PLAYING` they flush as the standalone `ev`
  message, and the `countdown` / `round` state frames reach every
  connection. `UNDERCOOKED_SIM_LATENCY_MS` applies the server-side send
  delay the netcode tests use to simulate RTT. The shape, the delta
  rules and a captured frame are `docs/PROTOCOL.md` ("The `snap`
  frame"), the no-leak/quantization guard is
  `tests/unit/test_encoding_no_leak.py`, and the budgets (a 4-player /
  4-order frame ≤ 1.5 KB, a 64×64 level ≤ 4 KB, the 100-tick downlink
  ≤ 60 KB/s) are measured over live sockets in
  `tests/integration/test_encoding.py`.
- **Disconnects, the ghost, and the rejoin (phase 06, task 05).** A
  dropped socket (an abrupt close, a heartbeat timeout, or the
  test-only `kill_socket` seam) keeps the seat for
  `UNDERCOOKED_GUEST_IDLE_TIMEOUT_S` (default 45 s): the other
  players see one `ghost_on` event and a `connected: false` seat, the
  sim's cook switches to `disconnected`, and after 3 s the cook's
  carried item is released — onto the station on the cook's tile (a
  marked set-down, grabbable), or into the `lost_items` counter when
  no station is under the tile (an item is never deleted silently). A
  `hello` with the same token inside the window rejoins the same seat
  (`welcome.rejoined: true`, one `ghost_off`, the snapshot stream
  resumes within one tick); past it the seat is abandoned (one
  `ghost_off`, the spectate/join rules apply, an emptied room closes
  through the 30 s seat grace / the GC). The client keeps the socket
  honest with a `ping` at ≥ 5 Hz; 12 s of inbound silence is a dead
  client (the server closes `1000` — the room sees the same drop as an
  abrupt close), and a closing room closes its sockets with
  `err room_gone` + close `4401`, so a client can tell "the room
  died" apart from "you left" (`1000`). The grace, the park, the
  ghost events and the close-code decision table are
  `docs/PROTOCOL.md` ("Heartbeats, drops, and seat grace"); the
  park's rules are `sim/ghost.py` (driven in
  `tests/unit/test_ghost_parking.py`), the drop/rejoin/seam paths in
  `tests/integration/test_ws_disconnect.py`.
- **The protocol, tested (phase 06, task 06).** The wire contract's
  final proof is three real-socket suites in `tests/integration/`:
  `test_ws_round_two_clients.py` (two scripted clients play a complete
  round — the countdown, the `snap` stream, the scripted soup, the
  shared `served` event and the byte-identical `round` frames, a
  mid-round spectator, the `to_lobby` return), `test_ws_abuse.py`
  (2000 malformed frames, the 500-message burst, the 64 KB refusal /
  4 KB boundary, the host-check and emote-throttle flood, 200
  concurrent handshakes) and `test_ws_budgets.py` (`slow`: the tick
  cost over 400 real ticks, the `snap` size, the downlink rate, the
  input→snapshot echo). The `live_server` / `ws_client` fixtures
  (`tests/integration/conftest.py`) drive them — a real `uvicorn`
  server on an ephemeral loopback port and a scripted client with a
  merged snapshot view (`expect` / `collect` / `send_model`). The
  contract, the test seams and the budget table with the measured
  values are `docs/PROTOCOL.md` ("Testing the protocol").
- **The canvas client, art, and the HUD (phase 07).** The browser half
  is live on top of all of this: the in-repo SVG atlas (`assets_src/`
  → the served copies in `app/static/assets/`; `gen_art_index`
  regenerates the `index.json`, and a missing or duplicated symbol
  fails the build, the expected ids deriving from the sim's own enums
  and the `sim/stations.py` pipeline tables), the screen state machine
  (the page's landing create/join, the lobby with its code copy,
  level picker, ready-up, start and seat chips, the 3-2-1 countdown,
  the round-end and the error screens, all on the same
  `WS /ws/{code}` socket), the snapshot buffer with the 100 ms
  interpolation and the event queue, the single render loop, the
  DPR-aware Canvas renderer (the kitchen floor, the stations, the
  y-sorted cooks, the carried items, the progress rings, the hazards,
  the particles, the target highlight) and the DOM HUD (the order
  rail, the score/target, the countdown with its non-colour cue, the
  streak, the dirty counter, the connection indicator, the spectator
  banner); the desktop keyboard input (WASD/arrows, the action
  button, the emotes, the `?` help overlay — the touch surface is
  phase 08) closes it out. `docs/CLIENT.md` is the module map and the
  contract; the proof is the e2e suites — `test_us01_create_lobby.py`,
  `test_us02_join_by_code.py`, `test_us03_ready_and_start.py` (the
  lobby flow), `test_us04_move_and_cook.py` (a scripted keyboard cook
  serves a soup) and `test_us04_render_smoke.py` (the canvas is
  provably not blank and moves after input; the HUD score changes
  within 200 ms of the `served` event), `test_us06_interp_math.py`
  and `test_us06_smoothness.py` (the interpolation math, exercised
  through a real page; per-tick displacement bounded with 60 ms of
  injected latency, both clients converge on `ROUND_END`), and
  `test_atlas_loads.py` (the atlas decodes with zero console errors;
  `test_us01_landing_surface.py` asserts the page's only network
  requests are same-origin).
- **The rules are tests, not promises.** The no-external-asset rule is
  `tests/unit/test_no_external_assets.py`, "no level or recipe id in Python" is
  `tests/unit/test_content_not_hardcoded.py`, the documentation set is guarded by
  `tests/unit/test_docs_index.py`, and `bash .agents/validate.sh` is the gate the
  phase pipeline runs after every task.

What does not exist yet: client prediction, reconciliation and the
touch surface (phase 08), the two-browser co-op E2E with
contested-resource arbitration (phase 09), the hazards and their
client FX (phase 10), the rest of the ten-level campaign (phase 11),
reconnect resilience and the 200-room stress run (phase 12), endless
mode with the session scoreboard (phase 13), and the accessibility
polish and hardening pass (phase 14). Execute phases with the
`phased-execution` skill (`auto-phase.sh`); it always takes the
lowest-numbered directory still in `.agents/phases/todo/`.

## How to play

The loop, live in the browser today: open the site, **Create lobby**, read out
the 5-character code, everyone else **Joins** with it, the host picks a level, the room
readies up, and the kitchen starts. Each cook has one movement control and **one action
button** that picks up, uses and puts down whatever is in reach — one carried item at a
time. Orders appear in the HUD with a shrinking deadline; assemble the dish and serve it
at the window before the timer runs out. Levels escalate: more recipes, fewer stations,
hostile floors. Nothing identifies you: the browser
keeps only a random per-tab token and the last code you typed, both in `sessionStorage`.
The campaign does remember per token — unlocks and best scores live server-side,
in memory, and a server restart clears all progression (A6: no database).

The page does that loop end to end: it loads,
normalises a typed code to five uppercase alphanumerics (codes
themselves are Crockford base32, minted by the room supervisor —
`server/rooms.py`, phase 05, also testable over `POST /api/rooms` /
`GET /api/rooms/{code}` / `POST /api/rooms/{code}/join` /
`GET /api/session`), the landing's **Create lobby** / **Join with code**
open a `WS /ws/{code}` socket (`hello` → `welcome` + `lobby`), the lobby
shows the code, the level picker (fed by `/api/levels`), the ready and
start controls and the seat chips, the 3-2-1 countdown runs, and the
round-end screen reports the verdict — the full contract, including the
guardrails and the close codes, is `docs/PROTOCOL.md`, the client's own
contract is `docs/CLIENT.md`. The playable Canvas renderer, the HUD and
the desktop keyboard controls are live (below; the in-game `?` help
overlay renders the same rows) — the touch controls arrive with phase 08.
The ready-up, the
20 Hz tick ownership, the
session store (the unlocks and best scores, in memory — a server restart
clears all progression) and the lifecycle integration suite are live.

### Controls

- **W / A / S / D** — move (or the arrow keys)
- **Space / Enter** — action (pick, work, set down, serve)
- **1 / 2 / 3 / 4** — emote (wave, cheer, thumbs up, thumbs down)
- **?** — help overlay
- **Esc** — close help / leave the room

The goal is the HUD's target score before the level's deadline: an order
ticket names a dish, and the action button does everything a hand does —
pick the ingredient off a shelf, work it on a station (hold the button
while the station works), plate it and serve it at the window. One
carried item at a time; a set-down marks the item so a partner can
pass it. `?` opens the help overlay (the same rows, rendered in-game);
`Esc` closes it — or leaves the room. The `?controls=off` URL param
disables the bindings (the touch surface's seam, phase 08).

## Quickstart (development)

Requires [`uv`](https://docs.astral.sh/uv/), Python ≥ 3.12, and `podman`/`docker`
for container builds. **There is no database** — all live game state is in memory.

```bash
uv sync --extra dev
uv run undercooked                 # http://127.0.0.1:8000 (shell page + /healthz)
uv run undercooked --host 0.0.0.0 --port 8000   # e.g. to reach it from a phone
uv run undercooked --reload        # dev reload
uv run undercooked --levels-dir levels          # point at another content dir
curl -fsS http://127.0.0.1:8000/api/levels      # the campaign cards the lobby will show
curl -fsS http://127.0.0.1:8000/api/config      # client-safe settings + protocol version
curl -fsS -X POST http://127.0.0.1:8000/api/rooms   # create a room: 5-char code + your token (201)
curl -fsS http://127.0.0.1:8000/api/rooms/<CODE>    # inspect it: the seat list, no tokens
curl -fsS -H 'X-Undercooked-Token: <TOKEN>' http://127.0.0.1:8000/api/session   # your session: unlocked, best (in memory; a restart clears it)
```

`python -m undercooked` is the same command (the container uses it). A flag
always beats the environment, which beats the built-in default. There is no
`/docs` or `/openapi.json`: FastAPI renders those pages from a public CDN, which
this project forbids. The validation the server runs at startup (every level
file loads, and no rule of PLAN §8 is broken) is a command too —
`undercooked-levels`, see **Authoring content** below.

Debug the server with a real debugger attached (dev only - the listener binds
`0.0.0.0`, so never enable it on a public host):

```bash
DEBUGPY=1 uv run undercooked       # opens a debugpy listener on :5678, then serves as usual
```

Authoring content:

```bash
uv run undercooked-levels list                        # the campaign, in campaign order
uv run undercooked-levels show 01_first_kitchen --grid  # resolved level + reachability overlay
uv run undercooked-levels validate                    # the content gate; --json for scripts
uv run undercooked-levels new 03_riverboat            # scaffold a level from the recipe book
uv run undercooked-levels axes                        # escalation-axis table (phase 11's curve)
uv run python -m undercooked.tools.gen_art_index      # rebuild app/static/assets/index.json from assets_src/
```

`undercooked-levels` is a thin shell over the loader and the PLAN §8 rules
`create_app` runs at startup, so a green `validate` is a server that boots. It
finds content through the settings (`--dir` > `UNDERCOOKED_LEVELS_DIR` >
`levels`, plus `--recipes` > `UNDERCOOKED_RECIPES_PATH` > `<dir>/recipes.yaml`)
and never from the current directory, so it works from any path. Exit codes:
`0` ok, `1` a level breaks a rule, `2` nothing usable to work with (load
failure, unknown id, refused overwrite, usage error). The schema, every field,
the overlay trick and a "which rule did I just hit" table live in
[docs/LEVELS.md](docs/LEVELS.md); `tests/unit/test_content_not_hardcoded.py`
is what keeps levels and recipes out of the Python. The in-repo SVG art
(phase 07 task 01) is guarded the same way: `gen_art_index` fails with the
missing id named when a symbol is absent or duplicated, and its expected set is
derived from the simulation's own enums and pipeline tables, so a new
`ItemKind`/`ItemForm` the sim can produce breaks the build until a symbol is
drawn for it (guards: `tests/unit/test_assets.py`,
`tests/e2e/test_atlas_loads.py`).

Run the checks:

```bash
uv run ruff check .
uv run pyright
uv run pytest                              # everything, coverage floor included
uv run pytest -m "not e2e"                 # the quick loop: no browser launches
uv run playwright install chromium         # once, before the first e2e run
uv run pytest -m e2e                       # browser suites only
uv run pytest -m slow tests/sim -q --no-cov  # the gate's slow stage: goldens + perf budgets
bash .agents/validate.sh                   # the pipeline gate: full suite + ruff + pyright
```

The replay goldens behind `tests/sim/test_replay.py` are checked the same way a
level is validated: `uv run python -m undercooked.sim.replay check
<tests/fixtures/replays/<name>.json>` runs the committed input script and
gates it on `tests/goldens/<name>.golden.json` (exit `0` match, `1` divergence
with the first divergent tick and the changed fields, `2` missing script/level/
golden). `record` writes a golden — the manual re-bless, legitimate only after a
deliberate sim-contract change recorded in the phase task; the contract is
[docs/SIMULATION.md](docs/SIMULATION.md) ("Replaying and re-blessing goldens").

`pytest` with no `-m` runs the browser suites too, so chromium has to be
installed for the pipeline gate. Those suites start the app themselves on a free
loopback port (`live_server` in `tests/conftest.py`) — nothing needs to be
running first, and no test ever listens on a routable interface.

`bash .agents/validate.sh` is the gate a phase task must pass before it moves to
`.agents/phases/complete/`. It stops at the first failure, in this order:
`ruff check .`, `pyright`, `undercooked-levels validate` (unconditional: the same
loader and PLAN §8 rules `create_app` runs at startup, so a campaign that cannot
validate cannot commit), the **full** `pytest` suite with the 90 % coverage floor,
the slow sim stage (`pytest -m slow tests/sim`: the replay goldens and the perf
budgets — the random-walk smoke and the full-pipeline run — named on their
own so a quick loop that skips them cannot let them slip through the gate),
then repo-hygiene checks (nothing tracked that `.gitignore`
excludes, no log drops or key material committed). Run it from the repo root or
from `.agents/`.

## Container

```bash
podman build -t undercooked -f Containerfile .
podman run --rm -p 8000:8000 undercooked
# or
podman compose up -d
```

## Configuration

All settings come from the environment, parsed once into
`undercooked.config.Settings` — the only module that reads the environment, so
nothing else in the codebase touches `os.environ`. Precedence: `undercooked` CLI
flags, then exported environment variables, then a local `.env` (found from the
current directory upwards; never commit it), then the built-in defaults. A blank value counts as
unset. Invalid values (`UNDERCOOKED_TICK_HZ=99`) raise `ConfigError` at startup
instead of half-configuring the server, and unusable content is refused the same
way — an unreadable `UNDERCOOKED_LEVELS_DIR` or a level that breaks a PLAN §8
rule prints the named-rule report and exits `2` (under `--reload` the reload
child reports and restarts instead; docs/LEVELS.md). `.env.example` and the table below list
every variable with its default; tests keep both in sync with `config.py`.

| Variable | Default | Meaning |
|---|---|---|
| `UNDERCOOKED_HOST` | `127.0.0.1` | Bind address |
| `UNDERCOOKED_PORT` | `8000` | Bind port |
| `UNDERCOOKED_TICK_HZ` | `20` | Server simulation rate (5-60) |
| `UNDERCOOKED_SNAPSHOT_HZ` | `20` | Snapshot broadcast rate to players (<= tick rate) |
| `UNDERCOOKED_MAX_PLAYERS` | `4` | Players per room (1-4) |
| `UNDERCOOKED_MAX_ROOMS` | `200` | Concurrent rooms before new rooms are refused |
| `UNDERCOOKED_LEVELS_DIR` | `levels` | Directory of level YAML files (`~` is expanded) |
| `UNDERCOOKED_RECIPES_PATH` | *(derived)* | Recipe book file; empty = `recipes.yaml` inside `UNDERCOOKED_LEVELS_DIR` (here: `levels/recipes.yaml`) |
| `UNDERCOOKED_STATIC_DIR` | *(derived)* | Directory served at `/static`; empty = `app/static/` beside the source (containers set it) |
| `UNDERCOOKED_LOBBY_IDLE_TIMEOUT_S` | `900` | Close empty/idle lobbies |
| `UNDERCOOKED_GUEST_IDLE_TIMEOUT_S` | `45` | Drop a disconnected player's seat after this |
| `UNDERCOOKED_MAX_MESSAGE_BYTES` | `4096` | Hard cap on inbound WS frame size |
| `UNDERCOOKED_MAX_INPUTS_PER_S` | `40` | Per-connection inbound message rate limit |
| `UNDERCOOKED_SIM_LATENCY_MS` | `0` | Injected server-side downlink latency (netcode tests) |
| `UNDERCOOKED_HELLO_TIMEOUT_S` | `5` | A WebSocket that sends no `hello` within this many seconds is closed (code 4400) |
| `UNDERCOOKED_TEST_MODE` | `0` | `1` = register the test-only seam route (`POST /api/test/kill_socket/...`); never set in production |
| `UNDERCOOKED_ALLOWED_ORIGINS` | *(empty)* | Comma-separated `Origin`s accepted on the WebSocket handshake; empty = same-host only |
| `DEBUGPY` | `0` | `1` = open a debugpy listener on `DEBUGPY_PORT` at startup |
| `DEBUGPY_PORT` | `5678` | debugpy listen port |

## Layout

```
src/undercooked/        server: FastAPI app, rooms, WebSocket protocol, simulation
src/undercooked/__main__.py  the `undercooked` command (CLI > env > default)
src/undercooked/config.py  typed env settings (the only `os.environ` reader)
src/undercooked/debug.py   DEBUGPY-gated debugger bootstrap
src/undercooked/sim/       pure simulation kernel: entities (`model`), grid geometry
                           (`grid`), content schema + loader (`recipe`, `level`,
                           `content` — the YAML contract is docs/LEVELS.md), the
                           level validator (`validation` — PLAN §8 named rules;
                           rule table in docs/LEVELS.md), the fixed-step tick (`step`,
                           `state_build`, `rng`, and the subsystem hooks `movement`
                           (+ `collision`, its pure geometry), `interact` (the action
                           button — reach zone, verb ladder, named denials, contested
                           arbitration, the long-press trash), `carry` (the hands — one
                           item per hand, the marked set-down and counter hand-off,
                           the always-available trash), `stations`, `freshness`,
                           `scoring`, `orders`, `hazards`, `round_state` —
                           contract in docs/SIMULATION.md), and the A5 purity guard
                           (`purity`, test-enforced)
src/undercooked/sim/replay.py  the replay harness: the input-script format, the golden
                        hashes, `run_script`/`compare`, and the record/check CLI
                        (docs/SIMULATION.md "Replaying and re-blessing goldens")
src/undercooked/tools/levels.py   the `undercooked-levels` author CLI — validate, list,
                        show [--grid], new, axes; same loader, same rules, no
                        hard-coded content list (docs/LEVELS.md "Authoring workflow")
src/undercooked/tools/gen_art_index.py  the SVG atlas index generator — rebuilds
                        app/static/assets/index.json from assets_src/; the expected
                        ids derive from the sim's enums + the station pipeline
                        tables, a missing or duplicated id fails (guards:
                        tests/unit/test_assets.py)
src/undercooked/server/app.py     app factory, `/healthz`, `/`, `/static`, mounts the
                        content API and the room API; installs the supervisor
src/undercooked/server/clock.py   injectable time: `Clock`, `SystemClock`, `FakeClock`
                        (the only server module that imports `time`; a grep
                        test keeps the wall clock out of the rest of `server/`)
src/undercooked/server/codes.py   Crockford room codes: the alphabet, collision-checked
                        minting (`new_code`), input normalisation (confusables,
                        malformed ≡ unknown, US-02 criterion 4)
src/undercooked/server/room.py    `Room`: code, seats (the rejoin path keeps
                        disconnected seats), `RoomState`, one owned tick task
src/undercooked/server/rooms.py   `RoomSupervisor`: the registry, capacity, the
                        one-token-one-room index, the 5 s GC, `start`/`shutdown`
src/undercooked/server/sessions.py `SessionRecord` + `BestRun` + `mint_token`
                        + the bounded LRU `SessionStore` (`record_result`'s win-only
                        unlock bump, best-score replacement, `is_unlocked` /
                        `next_level_id`, `to_public` — in memory; a process
                        restart clears all progression)
src/undercooked/server/routes_rooms.py  `POST /api/rooms`, `GET /api/rooms/{code}`, `POST
                        /api/rooms/{code}/join`, `GET /api/session` — the lifecycle
                        over HTTP before the phase-06 WebSocket transport (session
                        from the `X-Undercooked-Token` header or the body's
                        `token`, minted otherwise; tokens returned once; seats never
                        leak tokens)
src/undercooked/server/routes_content.py  `/api/levels`, `/api/levels/{id}`, `/api/config`,
                        plus the startup gate: broken content refuses startup
src/undercooked/server/headers.py the security-header middleware
.env.example            every configuration variable, with its default
levels/                 data-driven content (YAML): the recipe book (A8) and the
                        first two campaign levels (01_first_kitchen, 02_double_shift)
assets_src/             the hand-authored SVG art (tiles, stations, items, cooks,
                        fx, ui) — source for the served copies in
                        app/static/assets/ (a guard test keeps them in sync)
app/static/             the browser client (ES modules, no bundler):
                        the composition root (`js/main.js`), the screen
                        state machine (`js/app.js`) and the seven screens
                        (`js/screens/`, the no-innerHTML DOM builder
                        `dom.js`), the snapshot buffer + 100 ms
                        interpolation (`js/net/`), the single render loop
                        (`js/render/loop.js`), the DPR-aware Canvas 2D
                        renderer (`js/render/canvas.js` + `camera.js` +
                        `fx.js`), the DOM HUD (`js/ui/hud.js`), the
                        desktop keyboard input (`js/input/keyboard.js`)
                        and the help overlay (`js/ui/help.js`); the
                        in-repo SVG atlas with its `index.json`, the
                        palette (`assets/palette.css` +
                        `js/render/palette.js`, kept hex-identical by a
                        test) and the atlas loader (`js/render/atlas.js`)
                        (contract: docs/CLIENT.md)
tests/                  unit/, integration/, e2e/ (one Playwright suite per story) and
                        sim/ (the pure kernel: grid, entities, purity guard, validation,
                        the seeded RNG and the tick; plus the replay harness — committed
                        goldens in goldens/, scripts in fixtures/replays/ — and the
                        `slow` perf budgets (the random-walk smoke and the
                        full-pipeline run));
                        fixtures/levels/ is the content dir tests see (a recipe book and no
                        levels; `_bad/` holds the deliberately-broken campaign the `_`
                        discovery rule ignores); conftest.py
docs/                   DESIGN.md, LEVELS.md (the level & recipe YAML contract),
                        SIMULATION.md (the tick contract), ROOMS.md (rooms &
                        lobby lifecycle), PROTOCOL.md (the v1 wire contract —
                        message tables, error/close codes, limits, the full-round
                        sequence, the test seams and the budget table), CLIENT.md
                        (the client module map, the render loop, the snapshot
                        buffer, the input, the assets), TESTING.md (how this
                        project is verified), DEPLOYMENT.md (the index is
                        PLAN.md §13)
.agents/                PLAN.md, user_stories/, phases/, validate.sh — the phased-execution plan
```

**No external CDNs.** Every byte of JS, CSS, font, and image is served by this app
from `app/static/`. `tests/unit/test_no_external_assets.py` enforces it, and the
e2e suite fails if loading the page ever issues a request off-origin.

## Contributing

Read [AGENTS.md](AGENTS.md) first: it points at `.agents/PLAN.md` (LOCKED decisions)
and the phase protocol. Code changes land by executing phase task files, not by
editing ad hoc.