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transcience/CLAUDE.md
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Documentation pass before context compaction
The roadmap was actively misleading: an earlier stage renumbering left Stage 2's
completed work sitting under a "Stage 3 -- todo" heading, and the inventory
table orphaned with no heading at all. Since that file is the primary handoff
document, a fresh session would have started by re-implementing accounts and
characters. Rewritten.

Captured in full, from the original brief rather than from memory, the two
stages not yet built:

- Stage 3 (inventory and loot): 4 slots, potions rare from trash and guaranteed
  from bosses, world-shared loot, and the player-instanced food item -- with a
  note that two loot visibilities must exist from the start, because proving the
  instanced path works is the food item's entire purpose.
- Stage 4 (upgrades): every upgrade with its exact stated effect, plus the two
  constraints it will collide with -- sniper's 2x bullet speed against the
  tunnelling threshold, and per-player bullet travel against the interest radius
  that test_interest.gd currently derives from static content.

Ten open questions are listed as explicitly do-not-guess, seven of them blocking
Stage 4.

ARCHITECTURE.md still claimed "the arena is a rectangle" and "no tilemap
collision", both untrue since Stage 1. Rewritten around MapGrid, with what the
grid costs (axis-aligned, 32px-quantised, bullets under a tile per tick) rather
than only what it buys.

Added a "verification traps" section to WORKFLOW.md recording six mistakes made
during this work, each of which cost a round trip of reporting something fixed
that was not: verifying the artefact rather than the behaviour, dumping the
wrong channel, measuring a configuration where the bug cannot exist, a test
whose setup silently invalidated it, git checkout reverting real work alongside
a probe, and a pattern edit matching in two files. They are specific enough to
be actionable.

Also documented the diagnostics in CLAUDE.md -- they were undiscoverable -- and
recorded the current verification surface so "everything passes" has a stated
meaning.

206 tests, 15 smoke assertions, both diagnostics pass.
2026-09-04 20:34:45 +02:00

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Markdown

# Transcience
Top-down twin-stick bullet-hell with a dedicated, server-authoritative backend.
Godot 4.7, GDScript only. One executable is both server and client.
**Starting a new session?** [docs/ROADMAP.md](docs/ROADMAP.md) says what is
built, what is next, and which file implements each feature.
[docs/DECISIONS.md](docs/DECISIONS.md) records what the user has already decided
and why — read it before asking a design question, several answers there are not
the obvious default.
## Commands
```bash
tools/check.sh # parse-check every script (~5s) -- run after every edit
tools/test.sh # GUT suite, headless (~3s)
tools/smoke.sh # real server + 4 bot clients over ENet (~40s)
tools/server.sh # dedicated server
tools/client.sh --listen # host and play, no menu
```
Diagnostics. Each runs as a *scene* (they need the `Net` autoload) and exits
non-zero on failure, so they gate like tests:
```bash
godot --headless --path . res://tools/diag_prediction.tscn # prediction gap; injects clock drift
godot --headless --path . res://tools/diag_progression.tscn # kill -> xp -> level -> death -> roster
godot --headless --path . --script tools/bench.gd # sim cost per tick
python3 tools/build_local_assets.py # rebuild the local-only bullet atlas
```
`diag_progression` exists because the bot smoke test cannot cover progression:
bots are poor shots and rarely kill anything.
Everything after `--` goes to `GameOpts.parse()`:
| Flag | Effect |
| --- | --- |
| `--server` | Dedicated server, no view. |
| `--join` | Skip the menu and connect. |
| `--listen` | Skip the menu and host a listen server with a local player. |
| `--bot` | Scripted input instead of the keyboard. Implies `--join`. |
| `--host`, `--port`, `--name` | Connection details. |
| `--autoquit N` | Quit after N physics ticks. |
| `--boss-rush` | Server-side: dungeons spawn the boss and no trash. |
| `--depth N` | Server-side: depth of new dungeons, which drives map size. |
| `--account N` | Client-side: override the local account, so several clients can coexist on one machine. |
| `--store PATH` | Server-side: character store location. Use a scratch path in tests. |
| `--verbose` / `--quiet` | Log level. |
A change is done when `check.sh`, `test.sh` and — if it touched networking,
instances or the simulation — `smoke.sh` all pass. Say so explicitly; do not
report a networking change as working on the strength of unit tests alone.
## Hooks
`tools/install-hooks.sh` once per clone (points `core.hooksPath` at
`.githooks/`, committed in the repo — plain bash, no `pre-commit` framework, so
cloning costs nothing extra to run tools/*.sh). Own `.gd` files (not vendored
`addons/`) trigger `check.sh` + `test.sh` on commit (~7s); `smoke.sh` runs on
push (~35s, skip deliberately with `SKIP_SMOKE_HOOK=1 git push`).
## The one rule
**The server decides everything; the client only sends intent.**
A client can send exactly two things: an [InputFrame] (move vector, aim angle,
three button bits) and a handshake. There is no message for "I moved here", "I
hit that", "I took damage" or "my escape finished". Adding one would collapse
the whole security model, so don't — validate-after-the-fact is strictly weaker
than having no code path at all.
`SimWorld.authoritative` is `true` on the server and `false` on the client. In
replica mode the world runs no AI, fires no emitters and resolves no hits; it
only integrates bullets it was told about. `tests/unit/test_server_authority.gd`
and `tests/integration/test_replica_parity.gd` pin this down.
## Layout
| Path | What lives there |
| --- | --- |
| `src/sim/` | The whole game as plain RefCounted objects. No nodes, no physics server, no rendering. |
| `src/sim/patterns/` | Bullet emitters — the authoring surface for every enemy and boss. |
| `src/sim/map_grid.gd` | Tile grid: collision, line of sight, chunk streaming. |
| `src/sim/map_gen.gd` | Dungeon generation; `build()` is the only entry point. |
| `src/content/rooms.gd` | Hand-authored room stamps (hub, boss arenas) as text. |
| `src/meta/` | Accounts, characters, persistence, XP curve. Server-owned. |
| `src/content/content.gd` | All enemies and bosses, defined in code. Source of truth. |
| `src/net/` | Codec, `ServerRuntime`, `ClientRuntime`. |
| `src/instances/` | Lobby hub and dungeon runs. |
| `src/view/`, `src/ui/` | Read-only rendering. Never decides anything. |
| `src/autoload/net.gd` | The only autoload. RPC surface. |
| `tools/` | Headless tooling. |
The simulation must not import anything from `src/net/`, `src/view/` or
`src/ui/`, and must not touch `Net`. That is what lets tests drive a thousand
ticks in milliseconds with no SceneTree.
## Godot gotchas that will waste your time
1. **New `class_name` needs a cache refresh.** `.godot/global_script_class_cache.cfg`
is only rebuilt by the editor or `godot --headless --path . --import`.
Until then every use of the new class reports `Identifier not declared`,
which looks like a real error. `check.sh` does the refresh for you.
2. **Autoload names do not resolve under `--script`.** A `--script` run has no
main loop, so `Net` is `Identifier not found`. Tools that need autoloads must
run as a scene (see `tools/check.tscn`); tools that don't can use `--script`.
This is why `GameLog` and `GameOpts` are static classes rather than autoloads.
3. **`ResourceLoader.load()` returns non-null for a broken script.** Never test
the return value to detect a parse error; read the engine's stderr instead.
And never call `Script.reload()` on the script you are running — it hangs.
4. **Input events default to `device = 16`, which matches nothing.** Bindings
must use `device = -1`. `tools/setup_input_map.gd` generates the input map
correctly; edit that file, not the `[input]` block in `project.godot`.
5. **`set_anchors_preset(preset)` does not zero the offsets.** `keep_offsets`
defaults to `false`, which despite the name means "recompute offsets to keep
the control's *current* rect on screen" — for a freshly created Control that
rect is `(0,0)`-sized, so it comes out pinned to the top-left corner
regardless of the anchors. Use `set_anchors_and_offsets_preset()` for any
Control built in code. Separately: `.position` assigns an *absolute*
coordinate even on an anchored control; `offset_left`/`offset_top` are the
anchor-relative ones. This combination silently broke the main menu and
three pieces of the HUD.
6. **`ProjectSettings.save()` drops settings equal to the engine default** and
strips comments. Anything load-bearing (the 60 Hz tick) is asserted in code
in `src/main.gd` instead of trusted to `project.godot`.
## Non-obvious invariants
- **`ClientRuntime.process_physics_priority = -10`.** The client must sample and
send input before `ServerRuntime` ticks, or a listen server's drawn ship sits
a permanent tick ahead of the authoritative one and bullets trail it. Measure
with `godot --headless --path . res://tools/diag_prediction.tscn` (~0.1px is
healthy, 4px means the ordering broke).
- **`PLAYER_RADIUS` (hitbox) < `PLAYER_VISUAL_RADIUS` (sprite), and
`PLAYER_MUZZLE_OFFSET` derives from the visual one.** Prefer a visible
near-miss over an invisible hit; keep the muzzle clear of the sprite.
- **`INPUT_MAX_LEAD` must stay well above `INPUT_LEAD_MAX`.** The server's
input acceptance window has to be wider than the band in which the client
re-syncs its own numbering. Violate it and drifting clocks land in a silent
dead zone where the server rejects everything and the client never notices —
the ship and the authoritative position separate permanently. Pinned by
`tests/unit/test_input_lead.gd`.
- **Never send the map, or its seed.** Geometry is streamed per peer in chunks
around that peer's player (`ServerRuntime._stream_map`). The seed would let
any client regenerate the whole dungeon. `MAP_STREAM_RADIUS` must stay wider
than `FOG_VIEW_RADIUS`, or prediction runs on terrain the client lacks.
- **Bullet speed must stay under one tile per tick.** Wall collision samples
position once per tick, so anything faster tunnels. Pinned by
`test_bullet_speeds_stay_below_the_tunnelling_threshold`.
- **Only `ServerRuntime` writes progression.** The simulation reads a player's
level and max health; it never grants experience or retires a character. One
writer means a level can never disagree with the experience that earned it.
- **`LocalAuthProvider` is insecure on purpose.** Any client can claim any
account. It exists to have the same shape as Steamworks (opaque ticket in,
64-bit account id out) so swapping is one class. Do not ship it.
- **No contact damage.** Every enemy threatens through bullets only; touching
one is harmless. `tests/unit/test_content.gd` enforces that every hostile has
an emitter.
- **No i-frames.** Every bullet that touches a player lands; `spawn_grace` is
the only invulnerable state. Do not reintroduce post-hit immunity — it makes
dense patterns safer than sparse ones.
- **A disconnect is not an exit.** Dropping in a dungeon keeps the player in the
world as `linkdead`, channelling out over the same second the escape costs.
Damage must never cancel the escape channel, or quitting beats the button.
See [docs/NETCODE.md](docs/NETCODE.md).
## Adding content
A new enemy or boss is data, never code. Add a builder to
`src/content/content.gd` returning an `EnemyDef` / `BossDef` made of the
emitters in `src/sim/patterns/`, register its id in `enemy()` / `boss()`, and
add a test. `tests/unit/test_boss.gd::test_a_brand_new_boss_needs_no_engine_changes`
builds a boss from scratch and asserts the simulation needs no changes to run
it — if you find yourself adding a per-boss branch to `SimWorld`, stop and add
an emitter type instead.
`tools/export_content.gd` writes `.tres` copies into `resources/` for tuning in
the editor inspector. Those are an export, not the source; port changes back.
## Style
Typed GDScript everywhere (`untyped_declaration` is a warning). Tabs, snake_case
files, `PascalCase` class names. Comments explain *why* a thing is the way it is —
the netcode and anti-cheat decisions especially. Keep the existing density.