Complete the overworld foundation

Port forced movement (turn delays, bumps, ice, currents, pits), dynamic
return warps, elevators, Surf, Cut, Strength and cycling rules, working
map blocks with changeblock/changemapblocks, and the remaining NPC
movement types and movement commands.

Add tileset animation from the ROM's command tables, grass sprite
priority and special map palettes; room decorations with ownership, the
bedroom PC and save migration; and Key Items access to the Bicycle.

Fourteen original-engine traces compare positions, facing, actors, event
flags and scripted poses. Tile animation matches original VRAM for four
tilesets, and LoadMapPals matches 192 palette cases. skyfall_top now
keeps the $60 sprite offset its step function leaves behind.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/game/world/decorations.ts

@@ -0,0 +1,100 @@
+import { RomReader } from "../rom/reader";
+import { OVERWORLD } from "../rom/profile";
+import { PokemonData } from "../rom/pokemon";
+import { defaultTextContext, readString } from "../scripts/text";
+
+export const DECORATION_SLOTS = [
+  "bed",
+  "carpet",
+  "plant",
+  "poster",
+  "console",
+  "bigDoll",
+  "left",
+  "right",
+] as const;
+export type DecorationSlot = (typeof DECORATION_SLOTS)[number];
+export type Decorations = Record<DecorationSlot, number>;
+export const emptyDecorations = (): Decorations => ({
+  bed: 0,
+  carpet: 0,
+  plant: 0,
+  poster: 0,
+  console: 0,
+  bigDoll: 0,
+  left: 0,
+  right: 0,
+});
+export const initialDecorations = (): Decorations => ({
+  ...emptyDecorations(),
+  bed: 2,
+  poster: 16,
+});
+
+/** DecorationAttributes and GetDecoName, read from the user's ROM. */
+export class DecorationData {
+  constructor(
+    private reader: RomReader,
+    private pokemon: PokemonData,
+  ) {}
+  attribute(id: number) {
+    if (!Number.isInteger(id) || id < 0 || id > 52)
+      throw new Error("Invalid decoration.");
+    const p = OVERWORLD.DecorationAttributes + id * 6,
+      r = this.reader;
+    return {
+      type: r.byte(p),
+      name: r.byte(p + 1),
+      action: r.byte(p + 2),
+      event: r.word(p + 3),
+      sprite: r.byte(p + 5),
+    };
+  }
+  private word(index: number) {
+    let p = OVERWORLD.DecorationNames;
+    for (let i = 0; i < index; i++) {
+      while (this.reader.byte(p++) !== 0x50) {}
+    }
+    return readString(this.reader, p, defaultTextContext("PLAYER"));
+  }
+  name(id: number) {
+    const a = this.attribute(id);
+    if (a.type === 1) return this.word(a.name);
+    if (a.type === 2 || a.type === 3)
+      return this.word(a.name) + this.word(a.type === 2 ? 13 : 14);
+    const mon = this.pokemon.speciesName(a.name);
+    return a.type === 6
+      ? this.word(17) + mon
+      : mon + this.word(a.type === 4 ? 15 : 16);
+  }
+  owned(events: Set<number>, action: number) {
+    return Array.from({ length: 52 }, (_, i) => i + 1).filter((id) => {
+      const a = this.attribute(id);
+      return a.action === action && events.has(a.event);
+    });
+  }
+  valid(value: unknown, events: Set<number>): value is Decorations {
+    if (
+      !value ||
+      typeof value !== "object" ||
+      Array.isArray(value) ||
+      Object.keys(value).length !== 8
+    )
+      return false;
+    const slots = value as Decorations;
+    return (
+      DECORATION_SLOTS.every((slot, i) => {
+        const id = slots[slot];
+        return (
+          Number.isInteger(id) &&
+          id >= 0 &&
+          id <= 52 &&
+          (id === 0 ||
+            (this.attribute(id).action === (i < 6 ? i * 2 + 1 : 13) &&
+              events.has(this.attribute(id).event)))
+        );
+      }) &&
+      (!slots.left || slots.left !== slots.right)
+    );
+  }
+}