MRPGI/MANUAL.md

# MRPGI — The Complete Manual

**Monster Robot Party Game Interpreter** — a new-school, Apple-Silicon-native
reimagining of Sierra's 1980s AGI adventure engine, written in Rust + macroquad.
You paint rooms, drop in objects, write puzzles, and walk through them — with a
text parser, optional local-AI understanding, branching dialogue, chiptune sound,
and ambient music. No external level files, no build step beyond `cargo`.

This manual is exhaustive. Jump around with the table of contents.

---

## Table of contents
1. [What MRPGI is](#1-what-mrpgi-is)
2. [Install & requirements](#2-install--requirements)
3. [Running it](#3-running-it)
4. [The two modes](#4-the-two-modes)
5. [Core concepts (read this)](#5-core-concepts-read-this)
6. [The editor — full reference](#6-the-editor--full-reference)
7. [Keyboard cheat sheet](#7-keyboard-cheat-sheet)
8. [Building a world (rooms & exits)](#8-building-a-world-rooms--exits)
9. [Objects & game logic](#9-objects--game-logic)
10. [The parser](#10-the-parser)
11. [The AI parser lane](#11-the-ai-parser-lane)
12. [Dialogue trees](#12-dialogue-trees)
13. [Sound & music](#13-sound--music)
14. [The art / sprite pipeline](#14-the-art--sprite-pipeline)
15. [The kit & theme packs](#15-the-kit--theme-packs)
16. [Games as folders & the file formats](#16-games-as-folders--the-file-formats)
17. [Programmatic control (CLI · HTTP · MCP · Python)](#17-programmatic-control-cli--http--mcp--python)
18. [Project layout & architecture](#18-project-layout--architecture)
19. [Troubleshooting](#19-troubleshooting)
20. [Roadmap & known gaps](#20-roadmap--known-gaps)

---

## 1. What MRPGI is

AGI was the engine behind *King's Quest*, *Space Quest*, and *Police Quest*. Its
genius was a **dual-buffer** model: every room is drawn into a *visual* screen
(what you see) **and** a hidden *priority* screen (depth + walkability). MRPGI
keeps that soul and modernizes everything around it:

- **In-engine room editor** — paint walls, floors, and walkability by hand.
- **Sprite pipeline** — drop PNGs in a folder; they're auto-quantized to EGA.
- **Multi-room worlds** with edge exits.
- **Objects** with descriptions, locks, keys, and win conditions — no code.
- **A forgiving parser** + an **optional local LLM** that understands plain English.
- **Branching dialogue**, **chiptune SFX**, and **ambient room music**.
- **Flags & gated puzzles** — multi-step quests authored as plain JSON.
- **A content kit**: 61 click-to-place archetypes across fantasy, sci-fi,
  monsters, "saucy" nightlife, and classic horror.
- **A fully headless core** — the same engine is drivable from the command
  line, HTTP, Python, or an AI over MCP, with no window (§17).

Everything saves to small, human-readable JSON: **a game is a folder** you can
zip, share, or have an LLM write. The engine builds with `cargo` into two
binaries: the GUI (`mrpgi`) and the headless multi-tool (`mrpgi-headless`).

---

## 2. Install & requirements

**Required:**
- **Rust** (stable, 1.85+). Install from <https://rustup.rs> or Homebrew.
- That's it for building — macroquad pulls its own dependencies and renders
  natively (Metal on macOS). No system libraries to install.

**Optional (for the AI parser):**
- **[Ollama](https://ollama.com)** running locally with a small instruct model
  (e.g. a Gemma 4B). Free, offline, private. Or an **OpenRouter** API key.

First build downloads the crate tree and takes a minute or two; subsequent builds
are seconds.

---

## 3. Running it

```sh
cargo run -p mrpgi            # build + run the GUI (dev)
cargo run -p mrpgi --release  # optimized build (smoother), slower first compile
./run.sh                      # convenience launcher that points the AI lane at your model
```

### Launch flags
| Flag | Effect |
|------|--------|
| *(none)* | Loads the game in the current directory (`game.json` + `rooms/room0.json`) and opens in the **editor**. |
| `--game DIR` | Load a game folder instead of the current directory (see §16). |
| `--sample` | Writes a 3-room "escape the party" demo (+ `game.json`) then runs it (existing rooms backed up to `*.json.bak`). |
| `--kit` | Generates the fantasy starter kit + placeholder sprites, and installs a 4-room fantasy world (existing → `.bak`). |

```sh
cargo run -p mrpgi -- --kit                       # install + play the fantasy starter world
cargo run -p mrpgi -- --sample                    # install + play the robot escape demo
cargo run -p mrpgi -- --game games/lost-fuse      # play the example game (§16)
```

The headless binary takes the same `--game` / `--sample` / `--kit` flags:

```sh
cargo run -p mrpgi-core --bin mrpgi-headless -- --sample --game games/demo
```

### AI environment variables
| Var | Default | Meaning |
|-----|---------|---------|
| `MRPGI_AI` | `ollama` | `ollama` · `openrouter` · `off` |
| `MRPGI_AI_MODEL` | `gemma3:4b` | the model tag (set to YOUR Ollama tag) |
| `MRPGI_AI_URL` | `http://localhost:11434/api/generate` | endpoint override |
| `OPENROUTER_API_KEY` | — | required when `MRPGI_AI=openrouter` |

```sh
MRPGI_AI_MODEL="your-gemma-tag" cargo run
MRPGI_AI=openrouter OPENROUTER_API_KEY=sk-... MRPGI_AI_MODEL=google/gemma-2-9b-it:free cargo run
MRPGI_AI=off cargo run    # deterministic parser only
```

---

## 4. The two modes

MRPGI is always in one of two modes; **`Tab`** flips between them:

- **EDIT** — the painting/authoring mode. Left panel of tools, a canvas, a top
  strip for world/room controls. The engine boots here.
- **PLAY** — you become the robot. Walk with arrows or click, type commands, talk
  to NPCs. A bottom panel shows the transcript + command line.

`Esc` quits (in edit it first un-focuses a text field; in play it first ends a
conversation).

---

## 5. Core concepts (read this)

### The dual buffer — LOOK vs MEANING
Every pixel of a room has **two** independent properties:

- **LOOK** — its colour (one of 16 EGA colours). What the player sees.
- **MEANING** — what it *is* to the engine: walkable floor, a wall, water, a
  trigger, or a depth band. Stored in a hidden "priority" buffer.

**Colour does not imply meaning.** A brown floor and a brown wall look identical
but behave differently. When you paint, you set a colour *and* (optionally) a
meaning tag; they're applied to the same region but stored separately. This is the
single most important idea in MRPGI.

### Meaning tags
| Tag | Effect on the priority buffer |
|-----|-------------------------------|
| **floor** | walkable, with automatic depth (lower on screen = drawn in front) |
| **wall** | blocked — the robot can't enter |
| **water** | reserved (special) |
| **trigger** | reserved (signal line for future logic) |
| **none** | paint colour only; leave walkability unchanged |

By default an empty room is **entirely walkable** — you paint *walls* where you
don't want walking.

### The picture
The play area is **160 × 168 logical pixels**, displayed at a **2:1 pixel ratio**
(each pixel is twice as wide as tall — classic AGI). Colours are the 16-colour
EGA palette (indices 0–15). A perfect circle drawn in art tools looks slightly
wide in-game; that's intentional retro flavour.

### EGA palette
`0` black · `1` blue · `2` green · `3` cyan · `4` red · `5` magenta · `6` brown ·
`7` light gray · `8` dark gray · `9` light blue · `10` light green ·
`11` light cyan · `12` light red · `13` light magenta · `14` yellow · `15` white.

### The ego
"Ego" is the AGI term for the player avatar (the little robot). Its position is
its **feet** (bottom-centre of its sprite), which is what determines its depth and
collision. In play it's blocked by `wall` pixels and walks off `exit` edges.

---

## 6. The editor — full reference

The editor screen: a **tool panel** on the left, the **canvas** on the right, and
a **world strip** across the top of the canvas.

### Tools (number keys, or click in the panel)
| Key | Tool | What it does |
|-----|------|--------------|
| `1` | **brush** | freehand paint with the current colour + meaning (size via `,` `.`) |
| `2` | **line** | click to add points; **right-click or Enter** finishes the polyline |
| `3` | **rect** | drag a filled rectangle |
| `4` | **fill** | flood-fill a sealed region (the bucket) — fast |
| `5` | **pick** | eyedropper; grab a colour off the canvas |
| `6` | **erase** | rub back to blank + walkable |
| `7` | **image** | stamp a sprite from `sprites/` (`[` `]` to choose, `R` to reload) |
| `8` | **oval** | drag a filled ellipse |
| `9` | **spawn** | click to set where the robot appears in play (cyan circle) |
| `0` | **object** | place a live object — see below |

### Colour & meaning
- **Palette** (left panel): click a swatch to set the current LOOK colour.
- **Meaning** buttons: floor / wall / water / trigger / none — the MEANING applied
  by fills, rects, brush, etc.

### View modes (`L` cycles)
- **look** — the plain picture.
- **both** — picture + walls tinted red, water blue, triggers green (so you can
  *see* what's walkable).
- **ctrl** — the raw meaning map (depth + control).

### The object tool & kit browser (`0`)
With the object tool active the panel shows **`kit [ ]: <name>`**. Press `[` `]`
to flip through 60+ ready-made archetypes (orc, console, cocktail, coffin…). Click
an empty spot to **stamp** the selected archetype, fully written. Cycle to
`(blank)` to drop a bare object named after the current sprite. Click an existing
object to **select** it; the inspector then shows editable fields:

- **name** — what the parser calls it.
- **look text** — response to `look`.
- **use text** — response to `use`/`open`.
- **needs item** — an item required to `use` it (empty = unlocked).
- **synonyms** — extra nouns it answers to (space-separated).
- **takeable / fixed** toggle, **wins** toggle, **delete**.

Click a field, type, `Enter` jumps to the next field, `Esc` finishes.

### The world strip (top)
- **room N** + `<` `>` — move between rooms (also `-` `=`). Switching auto-saves.
- **exits** `N E S W` — click to cycle each edge's target room number.
- **♪** — cycle the room's ambient music mood (off · calm · eerie · tense · jolly · spooky).

### Saving
- `K` saves the current room to `rooms/room<N>.json` (an editable list of strokes
  + objects + exits + spawn + music). `O` reloads it. `C` clears, `Z`/`Backspace`
  undoes. The game auto-loads `rooms/room0.json` on startup.

---

## 7. Keyboard cheat sheet

**Global:** `Tab` edit ⇄ play · `Esc` quit (or un-focus / end conversation) ·
`F1` CRT scanlines · `F2` mute sound + music.

**Editor:** `1`–`0` tools · `L` view · `[` `]` choose sprite / kit archetype ·
`,` `.` brush size · `-` `=` prev / next room · `Z`/`Backspace` undo · `C` clear ·
`K` save · `O` load · `R` reload sprites + kit.

**Play:** arrows / click to walk · type a command + `Enter` · `1`–`6` choose a
dialogue reply · `Esc` leave a conversation.

---

## 8. Building a world (rooms & exits)

A room is one screen. A world is rooms linked by their edges.

1. Paint a room. Leave a **walkable gap** in a wall where you want a doorway.
2. On the strip, set that edge's **exit** to a room number (e.g. `E: 1`).
3. Press `>` to go to that room (going past the last room makes a new blank one),
   paint it, and set a matching exit back.
4. In play, **walk off the edge with an exit** → you arrive in the target room,
   entering from the opposite side.

Rooms are files: `rooms/room0.json`, `room1.json`, … Room 0 is where the game
starts. The **spawn** tool sets each room's entry point (used if the edge you
arrive at is walled).

---

## 9. Objects & game logic

Objects are sprites you can interact with. Each carries:

- a **name** + **synonyms** (what the parser matches),
- **look text** (shown on `look`),
- **use text** (shown on `use`/`open`),
- **needs** — an item that must be in your inventory to `use` it,
- **wins** — using it successfully ends the game with a victory banner,
- **takeable** — whether `take` adds it to your inventory,
- **requires_flag** — a flag that must be true before `use` works,
- **sets_flag** — a flag set true when `use` succeeds.

This is enough for the classic adventure loop **with no code**:

> Put a `key` (takeable) in one room and a `gate` in another with **needs = key**,
> **use text** = *"The gate grinds open…"*, **wins = on**. Now: `take key` →
> travel → `use gate` → **win**.

### Flags — multi-step quests

**Flags** are named booleans that live for one play session (a game's
`game.json` can preset them). Objects and dialogue choices read and write them:

> A `lever` with **sets_flag = power_on**. A `door` with **requires_flag =
> power_on**, **wins = on**. Now `use door` says *"Nothing happens. Something
> else must come first."* until you `use lever`.

Chain `needs` (items) with `requires_flag`/`sets_flag` (state) and gated
dialogue (§12) and you get real multi-step quests — all data, no code. The
example game `games/lost-fuse/` demonstrates the whole chain (§16).

Taking an object removes it from the room (runtime only — it returns on a fresh
play). Objects do not block movement (walls come from the painted meaning layer).
Currently `requires_flag`/`sets_flag` are JSON-authored (the editor inspector
shows the older fields only).

---

## 10. The parser

Type a sentence; it's lower-cased, filler words are dropped, the first word maps to
a canonical verb, and the rest is the noun (matched against object names +
synonyms, loosely).

**Verbs (and their synonyms):**
- **look** — look, l, examine, x, inspect, check, read, view, see, study
- **take** — take, get, grab, pick, snatch, steal, pocket, collect, nab
- **use** — use, open, unlock, activate, push, pull, turn, operate
- **drop** — drop, discard, leave, put
- **talk** — talk, speak, ask, chat, greet, say
- **inventory** — inventory, inv, i, items, bag
- **help** — help, ?, commands, verbs

**Ignored filler:** the, a, an, at, to, with, on, of, my, your, some, please, go, up.

`look` with no noun (or `look around`) lists what's in the room. Unknown verbs fall
through to the AI lane (if enabled) or print "I don't understand".

---

## 11. The AI parser lane

When the deterministic parser can't recognise your verb, MRPGI can hand the raw
sentence to a small LLM, which translates it into **one allowed command** — then
re-runs *that* through the normal logic. The AI bends the *language*; your game
still decides what's *possible*. It never invents items or outcomes, and it runs on
a background thread so the game never stalls. The chosen command is shown as
`(≈ open crate)`.

**Setup (local, recommended):** run Ollama with an instruct model and point MRPGI
at it via `MRPGI_AI_MODEL` (see §3). Default provider is `ollama`. If Ollama isn't
running or the model is missing, the lane stays silent and you get the normal
deterministic behaviour — nothing breaks.

**OpenRouter:** set `MRPGI_AI=openrouter`, `OPENROUTER_API_KEY`, and a
`MRPGI_AI_MODEL` like `google/gemma-2-9b-it:free`.

The bottom bar shows `ai: ollama/<model>` (or `off`).

---

## 12. Dialogue trees

An object can carry a **branching conversation**. In play, `talk <name>` starts it:
the NPC speaks and you press a **number key (1–6)** to choose a reply. Choices jump
to other lines; some end the chat. `Esc` leaves. Walking pauses while you talk.

Dialogue is authored as a `dialogue` array on the object (a visual builder is
planned). Each entry is a **node**; node 0 is the entry. See the inn barkeep in
`rooms/room3.json` for a working example:

```json
"dialogue": [
  { "says": "You're for the cave, aren't you?",
    "choices": [
      { "text": "What's down there?", "goto": 1 },
      { "text": "Just passing through.", "goto": 3 }
    ] },
  { "says": "Orcs. Dark. A spellbook nobody should read aloud.",
    "choices": [ { "text": "Thanks.", "goto": -1 } ] }
]
```

A choice's **`goto`** is the next node index, or **`-1`** to end. A node with no
choices is a terminal line (shown, then the conversation ends).

### Gated choices

Choices can read and write flags (§9), which makes conversations part of the
puzzle chain:

```json
{ "text": "Hear that? I'm with the band.", "goto": 2,
  "requires_flag": "music_on", "sets_flag": "on_the_list" }
```

A choice with `requires_flag` is **hidden** until that flag is true — the
numbering the player sees always matches what they can pick. `sets_flag` fires
when the choice is chosen. So an NPC can refuse to say something until you've
done a thing, and telling them can unlock a door elsewhere.

---

## 13. Sound & music

By default all audio is **synthesized at runtime** (square waves → PCM, no
files), in the spirit of AGI's PCjr beeper — and any of it can be **overridden
per game with real audio files** (below).

**SFX (play mode):** a blip when you submit a command, a ding on `take`, a chime on
a successful `use`/`look`, a buzz when nothing matches, a whoosh on room change, a
4-note fanfare on **win**.

**Ambient music:** each room can loop one of five moods (calm / eerie / tense /
jolly / spooky), set with the **♪** strip button in the editor and saved per room.
It plays in play mode and switches as you move between rooms.

**`F2`** mutes music and SFX together. If a machine has no audio backend, everything
degrades to silence.

### Your own audio files

Drop files into the game folder and they replace the synth, cue for cue:

```
<game>/sfx/blip|pickup|confirm|error|door|win .wav|.ogg|.mp3
<game>/music/calm|eerie|tense|jolly|spooky .wav|.ogg|.mp3   (or 1.ogg … 5.ogg)
```

Anything you don't provide keeps its chiptune default. Prefer **OGG for
looping music** (MP3 encoders pad silence that clicks at the loop seam).

---

## 14. The art / sprite pipeline

Sprites live in `sprites/` as PNGs. On load, any image is **quantized to the EGA
palette** (with transparency from its alpha), so it depth-sorts and walks-behind
like native art. Replace any sprite and press **`R`** to reload.

**The sprite spec:**
- **PNG with transparency.** Transparent pixels are see-through.
- **Small, at game scale.** A prop is ~12–28 px tall; draw 1:1.
- **Filename = id.** lowercase, no spaces (`orc.png`). The object's `sprite` field
  references this name. A missing sprite shows as a magenta placeholder.
- **Bottom-centre = feet.** Stand the thing on the bottom edge of the canvas.
- **EGA colours** ideal but not required — load `palettes/mrpgi-ega.gpl` into
  Aseprite/Inkscape, or let the engine snap your colours on load.

**Aseprite:** Palette → Load Palette → `palettes/mrpgi-ega.gpl`; draw small;
export PNG to `sprites/`; press `R`.

**Inkscape:** set a tiny px page; Export PNG (transparent) to `sprites/`.

**AI (Gemini "Nano Banana" / Imagen):** each theme's `gemini_sprites.md` has a
shared STYLE line + per-sprite prompts. Generate on a solid magenta background, key
it out to transparency, save into `sprites/`. (See also `palettes/mrpgi-ega.gpl`
and `palettes/mrpgi-ega.hex`.)

---

## 15. The kit & theme packs

`cargo run -- --kit` generates the **fantasy starter kit** and installs a playable
4-room world (forest → cave → dungeon → inn, with a key/spellbook/altar quest).

The reusable library lives in `kit/`:
- **`kit/objects.json`** — 13 fantasy object archetypes.
- **`kit/locations/`** — prefab rooms (forest, cave, dungeon, inn).
- **`kit/ART_MANIFESTO.md`** — exact sprite specs to replace the placeholders.
- **`kit/themes/{scifi,monsters,saucy,horror}/`** — each with `objects.json`
  (12 archetypes), a sample `locations/*.json`, and `gemini_sprites.md`.

**Use an object:** the kit browser (object tool, `[` `]`) stamps any of these by
clicking. Or copy a `{ … }` block from any `objects.json` into a room's `objects`
array. **Use a location:** `cp kit/themes/horror/locations/crypt.json rooms/room5.json`,
then wire its exits in the editor.

---

## 16. Games as folders & the file formats

**A game is a folder.** Zip it, share it, generate it with an LLM — the engine
loads it with `--game DIR` (both binaries):

```
games/mygame/
  game.json          the manifest (below) — optional, every field defaults
  rooms/room0.json   one RoomDoc per room; start room comes from the manifest
  sprites/*.png      auto-quantized to EGA; filename = sprite name
  sfx/  music/       optional audio-file overrides (§13)
```

A bare directory with just `rooms/` is already a valid game — that's how
legacy projects keep loading.

**game.json (the manifest):**
```json
{
  "name": "The DJ's Lost Fuse",
  "start_room": 0,
  "intro_text": "The party upstairs went quiet an hour ago. Type 'help'.",
  "verbs": [ { "name": "use", "words": ["plug", "spin"] } ],
  "flags": { "met_bouncer": false }
}
```
`verbs` merges extra synonyms into the built-in verb table (the AI lane's
whitelist is generated from the same table, so they can't drift). `flags` are
the starting flag values for each new game.

A complete worked example ships in **`games/lost-fuse/`** — three rooms
demonstrating every mechanic (items, locks, flags, gated dialogue, win), with
a guided tour in [`games/README.md`](games/README.md).

### Room file format (full schema)

A room is a `RoomDoc` serialized as JSON:

```json
{
  "strokes": [ <Stroke>, ... ],
  "spawn": [x, y],
  "exits": [N, E, S, W],          // each: a room number or null
  "objects": [ <ObjDef>, ... ],
  "music": 0                       // 0=silence, 1..5 = mood
}
```

**Stroke** is an externally-tagged enum — exactly one key:
```json
{ "Rect":    { "x":0,"y":0,"w":160,"h":168,"color":2,"meaning":"Floor" } }
{ "Line":    { "pts":[[x,y],...], "color":15 } }
{ "Brush":   { "pts":[[x,y],...], "color":6,"meaning":"Wall","size":2 } }
{ "Ellipse": { "x":..,"y":..,"w":..,"h":..,"color":..,"meaning":"None" } }
{ "Fill":    { "x":..,"y":..,"color":..,"meaning":"Floor" } }
{ "Image":   { "name":"crate","x":..,"y":..,"meaning":"Wall" } }
```
`meaning` is one of `"None"`, `"Floor"`, `"Wall"`, `"Water"`, `"Trigger"`.
`color` is an EGA index 0–15.

**ObjDef:**
```json
{
  "name": "gate", "sprite": "door", "x": 80, "y": 120,
  "look": "A heavy gate.", "takeable": false,
  "synonyms": "door portcullis", "use_text": "It grinds open!",
  "needs": "key", "wins": true,
  "requires_flag": "power_on", "sets_flag": "gate_open",
  "dialogue": [ <DlgNode>, ... ]
}
```
**DlgNode:** `{ "says": "...", "choices": [ { "text": "...", "goto": 1,
"requires_flag": "", "sets_flag": "" } ] }` — `goto` is a node index or `-1`
to end; the flag fields are optional (§12).

All fields except `name`/`sprite`/`x`/`y` default if omitted, so hand-written JSON
can be minimal. Strokes are *replayed* into the buffers on load, so rooms stay tiny
and re-editable.

---

## 17. Programmatic control (CLI · HTTP · MCP · Python)

The engine core is fully headless: a `GameState` driven by JSON `Command`s in
and `Event`s out. The GUI is just one consumer of that bus — the same bus is
exposed as:

- **JSONL stdio** — `mrpgi-headless --game DIR`; pipe
  `{"cmd":"parse","text":"take key"}` lines in, events stream out.
- **Script replay** — `--script play.jsonl` replays a command log
  deterministically (byte-identical transcripts; the CI golden-test workflow).
- **Headless render** — `--render-room rooms/room0.json out.png` bakes any
  room to a PNG with no window.
- **HTTP** — `--serve 127.0.0.1:7777`: `POST /command`, `GET /state`,
  `GET /frame.png`, `GET /events?since=N`, `POST /rooms/{n}`. Python drives it
  with plain `requests`.
- **MCP** — `--mcp`: a Model Context Protocol server, so Claude (or any MCP
  client) can both *play* the game and *author* it — including
  `mrpgi_render_frame`, which returns a real PNG so the model sees its work:
  `claude mcp add mrpgi -- /path/to/mrpgi-headless --mcp --game games/mygame`

Full command/event reference and authoring contract:
**[docs/CONTROL.md](docs/CONTROL.md)**.

---

## 18. Project layout & architecture

Two crates in one workspace:

```
mrpgi-core/            the headless engine (ZERO window/audio deps — enforced)
  src/state.rs         GameState + the Command/Event bus + fixed-step tick
  src/world.rs         RoomDoc/ObjDef/dialogue data model, World, game folders
  src/parser.rs        data-driven verb table, verb-noun parser, dialogue state
  src/render.rs        headless compositing → RGBA / PNG
  src/framebuffer.rs   visual + priority buffers, the band(y) depth table
  src/picture.rs       drawing primitives (lines, rects, flood-fill, stamps)
  src/view.rs          sprites as cels; ASCII-grid cel builder
  src/sprite.rs        the ego + props: movement, collision, walk-cycle
  src/assets.rs        PNG load + EGA quantize/dither; placeholder sprites
  src/audio.rs         chiptune synthesis + audio cues (content, not output)
  src/ai.rs            the AI parser lane (Ollama / OpenRouter, worker thread)
  src/kit.rs           sample game + starter kit writers
  src/bin/mrpgi-headless/   the CLI/HTTP/MCP surfaces
  tests/engine.rs      parser goldens + a full win-path replay test
mrpgi/                 the macroquad GUI (one consumer of the bus)
  src/main.rs          window, play loop over Commands/Events, HUD
  src/editor.rs        the paint tool (commits edits through the same bus)
  src/sound.rs         audio out: game-folder files override the synth
kit/                   the archetype/theme library + art manifesto
games/                 game folders (lost-fuse example lives here)
sprites/ rooms/        the legacy in-place game (still loads fine)
palettes/              the EGA palette for Aseprite/Inkscape (.gpl, .hex)
```

**Rendering:** rooms rasterize into a 160×168 visual buffer + a priority buffer.
Each frame, the ego and props are drawn back-to-front by depth; a sprite pixel is
only drawn where `sprite_priority ≥ scenery_priority` (the walk-behind trick). The
result is composited headlessly in the core; the GUI just uploads it to a GPU
texture. A fixed-step "cycle" (20/s) drives movement, decoupled from frame
rate — which is why scripted replays are bit-identical.

---

## 19. Troubleshooting

- **Objects are little magenta squares** → that sprite PNG doesn't exist yet in
  `sprites/`. Make it (see §14) or it's just a placeholder; the object still works.
- **A fill flooded the whole screen** → your outline has a gap; the region wasn't
  sealed. `Z` to undo and close the gap.
- **Robot stuck after a room transition** → the edge you arrived at is walled;
  leave a walkable gap there (it otherwise falls back to the room's spawn).
- **AI does nothing** → check the bottom bar `ai:` readout; ensure Ollama is
  running and `MRPGI_AI_MODEL` matches a pulled model (`ollama list`). It only
  fires on *unknown verbs*.
- **No sound** → some machines lack an audio backend; MRPGI stays silent rather
  than crashing. Check `F2` isn't muted.
- **Typing a letter flipped a mode** → in play, letters go to the command line;
  use `Tab`/`F1`/`F2`/`Esc` (non-letters) for controls.

---

## 20. Roadmap & known gaps

- In-editor **dialogue-tree builder** and flag-field editing (both are
  JSON-authored for now; the `dialogue`/`requires_flag`/`sets_flag` fields
  work — the inspector just doesn't show them yet).
- The **kit-browser villager** has no built-in dialogue yet (the live inn one does).
- More theme packs; **title screen / world picker**; **save/load a playthrough**.
- Water/trigger control lines are reserved but not yet wired to behaviour.
- True-colour ("HD") background layer and polygon fill regions.
- **Strudel** live-coded music as a browser sidecar over the HTTP surface.
- Pathfinding for click-to-walk (today: greedy steering); cross-room NPC state.

---

*MRPGI — built from "let's reimagine AGI" into a complete, AI-assisted, audible
adventure-game maker. Have fun making weird little worlds.* 🤖🎸