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/effects.test.js

@@ -0,0 +1,77 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+import { apply, applyAll } from "../src/core/effects.js";
+import { GameWorld } from "../src/core/world.js";
+
+const compiled = {
+  game: { startRoom: "jetty" },
+  rooms: { jetty: { id: "jetty" }, tavern: { id: "tavern" } },
+  objects: {}, characters: { otto: { id: "otto", room: "jetty" } },
+  verbs: {}, interactions: [], dialogues: {}, scenes: {},
+};
+
+const fresh = () => new GameWorld(compiled);
+
+test("flags and vars", () => {
+  const w = fresh();
+  apply({ setFlag: "x" }, w);
+  assert.equal(w.flags.x, true);
+  apply({ setFlag: "x", value: false }, w);
+  assert.equal(w.flags.x, false);
+  apply({ setVar: "gold", value: 5 }, w);
+  apply({ addVar: "gold", value: -2 }, w);
+  assert.equal(w.vars.gold, 3);
+});
+
+test("inventory give/remove are idempotent-ish", () => {
+  const w = fresh();
+  apply({ give: "mug" }, w);
+  apply({ give: "mug" }, w);
+  assert.deepEqual(w.inventory, ["mug"]);
+  apply({ remove: "mug" }, w);
+  apply({ remove: "mug" }, w);
+  assert.deepEqual(w.inventory, []);
+});
+
+test("effects return events for engine machinery", () => {
+  const w = fresh();
+  assert.deepEqual(apply({ goTo: "tavern" }, w), { type: "goTo", room: "tavern" });
+  assert.deepEqual(apply({ playMusic: "calypso" }, w), { type: "playMusic", track: "calypso" });
+  assert.deepEqual(apply({ startDialogue: "d1" }, w), { type: "startDialogue", dialogue: "d1" });
+  assert.deepEqual(apply({ endGame: "win" }, w), { type: "endGame", ending: "win" });
+});
+
+test("moveTo mutates the world directly", () => {
+  const w = fresh();
+  apply({ moveTo: { character: "otto", room: "tavern" } }, w);
+  assert.equal(w.characters.otto.room, "tavern");
+});
+
+test("malformed effects throw", () => {
+  const w = fresh();
+  assert.throws(() => apply({ bogus: 1 }, w), /unknown effect key/);
+  assert.throws(() => apply({ setFlag: "x", give: "y" }, w), /exactly one key/);
+  assert.throws(() => apply({ setVar: "g", value: "five" }, w), /needs numeric value/);
+});
+
+test("applyAll skips nulls", () => {
+  const w = fresh();
+  const events = applyAll([{ setFlag: "a" }, null, { give: "mug" }], w);
+  assert.equal(events.length, 2);
+});
+
+test("world snapshot/restore round-trips", () => {
+  const w = fresh();
+  apply({ setFlag: "x" }, w);
+  apply({ give: "mug" }, w);
+  apply({ addVar: "n", value: 7 }, w);
+  const snap = w.snapshot();
+  const w2 = fresh();
+  w2.restore(snap);
+  assert.equal(w2.flags.x, true);
+  assert.deepEqual(w2.inventory, ["mug"]);
+  assert.equal(w2.vars.n, 7);
+  // snapshot is a deep copy: mutating the live world doesn't touch the save
+  w2.give("rope");
+  assert.deepEqual(snap.inventory, ["mug"]);
+});