SCUMM-style web adventure engine v0.1

Headless, data-driven core (no DOM, no eval): loader with one-pass
validation, verb-coin interaction resolution, polygon walkables with
Dijkstra pathfinding, branching dialogue with mid-conversation saves,
declarative JSON conditions/effects, versioned JSON saves.

Thin integration layer: asset manifest with graceful placeholders,
WebAudio music loop points (midi-playlist convention), canvas renderer
(hotspot boxes drawn where hitTest clicks), HUD model.

Web harness (web/) + skeleton example game exercising every feature.
69 tests (node --test), tools/run_all.sh gate, docs/SPEC.md design spec.
Verified end-to-end in a real browser: intro scene, walking, look/take,
room exits, dialogue choices.

tests/save.test.js

@@ -0,0 +1,77 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { Engine } from "../src/core/engine.js";
+import { SAVE_VERSION } from "../src/core/save.js";
+
+const example = JSON.parse(readFileSync(new URL("../example/game.json", import.meta.url), "utf8"));
+
+const fresh = () => {
+  let now = 0;
+  const e = new Engine(structuredClone(example), { clock: () => now });
+  e.newGame();
+  return { e, advance: (ms) => { now += ms; e.tick(ms); } };
+};
+
+test("save/load round-trip restores the whole world", () => {
+  const { e, advance } = fresh();
+  e.selectVerb("use");
+  e.click({ kind: "object", id: "mug", tags: ["container"] });
+  e.goTo("tavern");
+  e.world.setFlag("didSomething", true);
+  e.world.addVar("score", 42);
+  const save = e.save();
+
+  const e2 = new Engine(structuredClone(example), { clock: () => 0 });
+  e2.load(save);
+  assert.equal(e2.world.room, "tavern");
+  assert.deepEqual(e2.world.inventory, ["mug"]);
+  assert.equal(e2.world.flags.didSomething, true);
+  assert.equal(e2.world.vars.score, 42);
+  assert.equal(e2.phase, "playing");
+});
+
+test("save format is versioned and game-tagged", () => {
+  const { e } = fresh();
+  const data = JSON.parse(e.save());
+  assert.equal(data.version, SAVE_VERSION);
+  assert.equal(data.game, "skeleton-demo");
+  assert.ok(data.savedAt);
+});
+
+test("rejects saves from another game", () => {
+  const { e } = fresh();
+  const save = e.save();
+  const other = structuredClone(example);
+  other.meta.name = "different-game";
+  const e2 = new Engine(other, { clock: () => 0 });
+  assert.throws(() => e2.load(save), /save is for game/);
+});
+
+test("rejects future save versions", () => {
+  const { e } = fresh();
+  const data = JSON.parse(e.save());
+  data.version = 999;
+  assert.throws(() => e.load(JSON.stringify(data)), /newer than engine/);
+});
+
+test("rejects garbage saves", () => {
+  const { e } = fresh();
+  assert.throws(() => e.load("not json"), /not valid JSON/);
+  assert.throws(() => e.load("{}"), /no version/);
+});
+
+test("mid-dialogue save resumes at the saved node", () => {
+  const { e } = fresh();
+  e.goTo("tavern");
+  e.selectVerb("talk");
+  e.click({ kind: "character", id: "barkeep", tags: ["talker"] });
+  assert.equal(e.dialogue.current().node, "greet");
+  const save = e.save();
+
+  const e2 = new Engine(structuredClone(example), { clock: () => 0 });
+  e2.load(save);
+  assert.ok(e2.dialogue.active);
+  assert.equal(e2.dialogue.current().node, "greet");
+  assert.equal(e2.dialogueChoices().length, 2);
+});