Add native Crystal exploration port and reference tooling
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Sébastien QUEROL committed 2026-09-23 09:23:29 +02:00
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import { RomReader } from "./reader";
import { decompress } from "./lz";
import { NATIVE_MAPS, SYMBOLS } from "./profile";
import type {
Direction,
GameMap,
Tileset,
Palette,
Sprite,
FacingTile,
} from "../world/types";
/** The only layer that knows where Crystal stores its data. Everything is
* decoded from the supplied ROM, on demand, and cached only in memory. */
export class CrystalAssets {
readonly reader: RomReader;
private maps = new Map<string, GameMap>();
private tilesets = new Map<string, Tileset>();
private sprites = new Map<number, Sprite>();
constructor(bytes: Uint8Array) {
this.reader = new RomReader(bytes);
}
map(id: string): GameMap {
const cached = this.maps.get(id);
if (cached) return cached;
if (!Object.hasOwn(NATIVE_MAPS, id))
throw new Error("This area has not been ported yet.");
const [group, number] = id.split(":").map(Number);
const r = this.reader;
const header =
r.near(SYMBOLS.mapGroups + (group - 1) * 2, r.bank(SYMBOLS.mapGroups)) +
(number - 1) * 9;
const attributes = r.near(header + 3, r.byte(header));
const blockWidth = r.byte(attributes + 2),
blockHeight = r.byte(attributes + 1);
if (!blockWidth || !blockHeight || blockWidth > 64 || blockHeight > 64)
throw new Error("Invalid map dimensions.");
const scriptBank = r.byte(attributes + 6);
let p = r.near(attributes + 9, scriptBank) + 2;
const map: GameMap = {
id,
group,
number,
name: NATIVE_MAPS[id],
width: blockWidth * 2,
height: blockHeight * 2,
border: r.byte(attributes),
tileset: r.byte(header + 1),
environment: r.byte(header + 2),
paletteMode: r.byte(header + 7) & 15,
blocks: r.slice(r.far(attributes + 3), blockWidth * blockHeight),
warps: [],
backgroundEvents: [],
objects: [],
connections: [],
sceneScripts: [],
callbacks: [],
coordinateEvents: [],
};
const warpCount = r.byte(p++);
for (let i = 0; i < warpCount; i++, p += 5) {
map.warps.push({
y: r.byte(p),
x: r.byte(p + 1),
targetWarp: r.byte(p + 2),
targetMap: `${r.byte(p + 3)}:${r.byte(p + 4)}`,
});
}
const coordinateCount = r.byte(p++);
for (let i = 0; i < coordinateCount; i++, p += 8) {
map.coordinateEvents.push({
scene: r.byte(p),
y: r.byte(p + 1),
x: r.byte(p + 2),
script: r.near(p + 4, scriptBank),
});
}
const backgroundCount = r.byte(p++);
for (let i = 0; i < backgroundCount; i++, p += 5) {
map.backgroundEvents.push({
y: r.byte(p),
x: r.byte(p + 1),
kind: r.byte(p + 2),
script: r.near(p + 3, scriptBank),
});
}
const objectCount = r.byte(p++);
for (let i = 0; i < objectCount; i++, p += 13) {
map.objects.push({
id: i + 2,
sprite: r.byte(p),
y: r.byte(p + 1) - 4,
x: r.byte(p + 2) - 4,
movement: r.byte(p + 3),
hour1: r.byte(p + 5),
hour2: r.byte(p + 6),
palette: r.byte(p + 7) >> 4,
kind: r.byte(p + 7) & 15,
script: r.near(p + 9, scriptBank),
eventFlag: r.word(p + 11),
});
}
p = r.near(attributes + 7, scriptBank);
const sceneCount = r.byte(p++);
for (let i = 0; i < sceneCount; i++, p += 4)
map.sceneScripts.push(r.near(p, scriptBank));
const callbackCount = r.byte(p++);
for (let i = 0; i < callbackCount; i++, p += 3)
map.callbacks.push({
kind: r.byte(p),
script: r.near(p + 1, scriptBank),
});
p = attributes + 12;
for (const [direction, bit] of [
["up", 8],
["down", 4],
["left", 2],
["right", 1],
] as const) {
if (!(r.byte(attributes + 11) & bit)) continue;
const signed = (v: number) => (v > 127 ? v - 256 : v);
map.connections.push({
direction,
targetMap: `${r.byte(p)}:${r.byte(p + 1)}`,
y: signed(r.byte(p + 8)),
x: signed(r.byte(p + 9)),
});
p += 12;
}
this.maps.set(id, map);
return map;
}
tileset(map: GameMap): Tileset {
const key = `${map.tileset}:${map.group}`;
const cached = this.tilesets.get(key);
if (cached) return cached;
const r = this.reader,
base = SYMBOLS.tilesets + map.tileset * 15;
const graphics = decompress(r, r.far(base), 0x4000);
const meta = r.far(base + 3),
collision = r.far(base + 6);
// Each tileset contains 128 metatiles (4x4 8px tiles), each with four
// quadrant permissions for the 16px movement grid.
const result: Tileset = {
graphics,
metatiles: r.slice(meta, 128 * 16),
collision: r.slice(collision, 128 * 4),
paletteMap: r.slice(r.near(base + 13, r.bank(SYMBOLS.tilesets)), 128),
};
if ([1, 2, 4].includes(map.tileset)) {
const roof = r.byte(SYMBOLS.roofTypes + map.group);
if (roof !== 255)
result.graphics.set(
r.slice(SYMBOLS.roofs + roof * 9 * 16, 9 * 16),
0x0a * 16,
);
}
this.tilesets.set(key, result);
return result;
}
block(map: GameMap, x: number, y: number): number {
if (x < 0 || y < 0 || x >= map.width || y >= map.height) return map.border;
return map.blocks[Math.floor(y / 2) * (map.width / 2) + Math.floor(x / 2)];
}
collision(map: GameMap, x: number, y: number): number {
if (x < 0 || y < 0 || x >= map.width || y >= map.height) return 7;
const block = this.block(map, x, y);
if (block >= 128) throw new Error("Map contains an invalid block.");
return this.tileset(map).collision[block * 4 + (y % 2) * 2 + (x % 2)];
}
permission(collision: number): number {
return this.reader.byte(SYMBOLS.collisions + collision) & 15;
}
palette(offset: number): Palette {
return Array.from({ length: 4 }, (_, i) => {
const color = this.reader.word(offset + i * 2);
return [
Math.round(((color & 31) * 255) / 31),
Math.round((((color >> 5) & 31) * 255) / 31),
Math.round((((color >> 10) & 31) * 255) / 31),
];
});
}
palettes(map: GameMap, time: number): Palette[] {
const r = this.reader;
const group =
r.near(
SYMBOLS.environmentColors + map.environment * 2,
r.bank(SYMBOLS.environmentColors),
) +
time * 8;
const palettes = Array.from({ length: 8 }, (_, i) =>
this.palette(
map.tileset === 5
? SYMBOLS.housePalettes + i * 8
: SYMBOLS.backgroundPalettes + r.byte(group + i) * 8,
),
);
if (map.environment === 1 || map.environment === 2) {
const roof = SYMBOLS.roofPalettes + map.group * 8 + (time >= 2 ? 4 : 0);
const colors = this.palette(roof);
palettes[6] = [palettes[6][0], colors[0], colors[1], palettes[6][3]];
}
return palettes;
}
objectPalette(index: number, time: number): Palette {
return this.palette(SYMBOLS.objectPalettes + time * 64 + (index & 7) * 8);
}
sprite(id: number): Sprite | undefined {
// Variable decorations and Pokémon icons need separate decoders.
if (id < 1 || id >= 0xa0) return undefined;
const cached = this.sprites.get(id);
if (cached) return cached;
const r = this.reader,
p = SYMBOLS.sprites + (id - 1) * 6;
const length = r.byte(p + 2),
walking = r.byte(p + 4) === 1;
const sprite = {
graphics: r.slice(r.near(p, r.byte(p + 3)), length * (walking ? 2 : 1)),
palette: r.byte(p + 5),
walking,
};
this.sprites.set(id, sprite);
return sprite;
}
facing(direction: Direction, frame: number): FacingTile[] {
const facing =
["down", "up", "left", "right"].indexOf(direction) * 4 + (frame % 4);
const r = this.reader,
pointer = r.near(SYMBOLS.facings + facing * 2, r.bank(SYMBOLS.facings));
return Array.from({ length: r.byte(pointer) }, (_, i) => {
const p = pointer + 1 + i * 4;
return {
y: r.byte(p),
x: r.byte(p + 1),
attributes: r.byte(p + 2),
tile: r.byte(p + 3),
};
});
}
}
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import { RomReader } from "./reader";
/** Native translation of Crystal's LZ data format (home/decompress.asm).
* Copy commands may overlap their own output. Addresses are relative to the
* decompressed stream, never arbitrary memory. */
export function decompress(
reader: RomReader,
offset: number,
limit = 0x10000,
): Uint8Array {
const output: number[] = [];
let cursor = offset;
const read = () => reader.byte(cursor++);
for (let commandCount = 0; commandCount < limit; commandCount++) {
const header = read();
if (header === 0xff) return Uint8Array.from(output);
let command = header >> 5;
let length = (header & 31) + 1;
if (command === 7) {
command = (header >> 2) & 7;
length = (((header & 3) << 8) | read()) + 1;
}
if (command === 7 || output.length + length > limit)
throw new Error("Invalid or oversized compressed graphic.");
if (command === 0) {
for (let i = 0; i < length; i++) output.push(read());
} else if (command === 1) {
const value = read();
for (let i = 0; i < length; i++) output.push(value);
} else if (command === 2) {
const a = read(),
b = read();
for (let i = 0; i < length; i++) output.push(i % 2 ? b : a);
} else if (command === 3) {
for (let i = 0; i < length; i++) output.push(0);
} else {
const first = read();
let source =
first & 0x80
? output.length - (first & 0x7f) - 1
: (first << 8) | read();
for (let i = 0; i < length; i++) {
if (source < 0 || source >= output.length)
throw new Error("Invalid compressed graphic back-reference.");
let value = output[source];
if (command === 5) {
value = ((value & 0x55) << 1) | ((value >> 1) & 0x55);
value = ((value & 0x33) << 2) | ((value >> 2) & 0x33);
value = ((value & 0x0f) << 4) | (value >> 4);
}
output.push(value);
source += command === 6 ? -1 : 1;
}
}
}
throw new Error("Compressed graphic has no terminator.");
}
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/** Addresses only, from PRET 7a7881d0d62e0ddbd82dcf10e7116807487ac651.
* RGBDS 1.0.3 crystal11 build was byte-identical to the user-supplied ROM.
* No original graphics, maps, dialogue, music or ROM instructions live here.
* See docs/NATIVE_PORT.md for source references and verification procedure. */
export const SYMBOLS = {
mapGroups: 0x94000,
tilesets: 0x4d596,
collisions: 0x4ce1f,
environmentColors: 0xb279,
backgroundPalettes: 0xb319,
objectPalettes: 0xb469,
roofPalettes: 0xb569,
roofTypes: 0x1c021,
roofs: 0x1c03c,
housePalettes: 0x495ee,
sprites: 0x14736,
facings: 0x4049,
standardScripts: 0xbc000,
} as const;
/** The currently ported area. Story callbacks are not executed yet. */
export const NATIVE_MAPS: Record<string, string> = {
"24:4": "New Bark Town",
"24:5": "Elm’s lab",
"24:6": "Your home",
"24:7": "Your room",
"24:8": "Neighbor’s house",
"24:9": "Elm’s house",
};
export const INITIAL_POSITION = { map: "24:7", x: 3, y: 3 } as const;
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/** Bounds-checked access to the user's cartridge. No CPU or hardware state. */
export class RomReader {
constructor(readonly bytes: Uint8Array) {}
byte(offset: number): number {
this.check(offset, 1);
return this.bytes[offset];
}
word(offset: number): number {
return this.byte(offset) | (this.byte(offset + 1) << 8);
}
slice(offset: number, length: number): Uint8Array {
this.check(offset, length);
return this.bytes.slice(offset, offset + length);
}
address(bank: number, address: number): number {
if (
!Number.isInteger(bank) ||
bank < 0 ||
bank >= this.bytes.length / 0x4000 ||
!Number.isInteger(address) ||
address < 0 ||
address >= 0x8000
) {
throw new Error("Invalid ROM bank or address.");
}
const offset =
address < 0x4000 ? address : bank * 0x4000 + address - 0x4000;
this.check(offset, 1);
return offset;
}
near(pointer: number, bank: number): number {
return this.address(bank, this.word(pointer));
}
far(pointer: number): number {
return this.near(pointer + 1, this.byte(pointer));
}
bank(offset: number): number {
this.check(offset, 1);
return Math.floor(offset / 0x4000);
}
private check(offset: number, length: number) {
if (
!Number.isInteger(offset) ||
!Number.isInteger(length) ||
offset < 0 ||
length < 0 ||
offset + length > this.bytes.length
) {
throw new Error(
"Cartridge data is truncated or contains an invalid pointer.",
);
}
}
}