diff --git a/src/main.js b/src/main.js
index 5e395cb..051d94e 100644
--- a/src/main.js
+++ b/src/main.js
@@ -1,43 +1,89 @@
 (() => {
   const { World, Body, Constraint, Events, Vector } = Matter;
 
-  const { config: baseConfig, defaultMessageConfig } = window.PhysilinksConfig
-    ?.create
-    ? window.PhysilinksConfig.create()
-    : {
-        config: {},
-        defaultMessageConfig: {
-          durationMs: 4200,
-          position: { xPercent: 50, yPercent: 10 },
-          text: null,
-          colors: null,
-        },
-      };
+  const fromWindow = (key, fallback = {}) => window[key] ?? fallback;
 
-  const config = {
-    ...baseConfig,
-    link: { ...(baseConfig?.link || {}) },
-    messages: { ...(baseConfig?.messages || {}) },
+  const getFactory = (key, fallbackFactory) => {
+    const mod = fromWindow(key);
+    return typeof mod.create === "function" ? mod.create : fallbackFactory;
+  };
+
+  const createConfig = getFactory("PhysilinksConfig", () => ({
+    config: {},
+    defaultMessageConfig: {
+      durationMs: 4200,
+      position: { xPercent: 50, yPercent: 10 },
+      text: null,
+      colors: null,
+    },
+  }));
+
+  const { config: baseConfig, defaultMessageConfig } = createConfig();
+
+  const normalizeMessages = (
+    sceneMessages = {},
+    defaults = defaultMessageConfig,
+  ) => ({
+    durationMs: Number.isFinite(sceneMessages.durationMs)
+      ? sceneMessages.durationMs
+      : defaults.durationMs,
+    text:
+      typeof sceneMessages.text === "string" && sceneMessages.text.trim()
+        ? sceneMessages.text.trim()
+        : defaults.text,
+    position: {
+      xPercent:
+        typeof sceneMessages.position?.xPercent === "number"
+          ? sceneMessages.position.xPercent
+          : defaults.position.xPercent,
+      yPercent:
+        typeof sceneMessages.position?.yPercent === "number"
+          ? sceneMessages.position.yPercent
+          : defaults.position.yPercent,
+    },
+    colors: Array.isArray(sceneMessages.colors)
+      ? sceneMessages.colors
+      : defaults.colors,
+  });
+
+  const normalizeSceneConfig = (sceneConfig = {}) => {
+    const { link = {}, messages = {}, ...rest } = sceneConfig;
+    return {
+      ...rest,
+      link: { ...link },
+      messages: normalizeMessages(messages),
+    };
+  };
+
+  const config = { ...normalizeSceneConfig(baseConfig) };
+
+  const setConfigForScene = (sceneConfig = {}) => {
+    const normalized = normalizeSceneConfig(sceneConfig);
+    Object.assign(config, normalized);
+    config.link = { ...normalized.link };
+    config.messages = normalized.messages;
   };
 
   const {
     scenes = [],
     defaultSceneId,
     order: sceneOrder = [],
-  } = window.PhysilinksScenes || {};
+  } = fromWindow("PhysilinksScenes", {});
 
   const { getSceneById, getSceneIdFromUrl, setSceneIdInUrl, getNextSceneId } =
-    window.PhysilinksSceneRegistry || {};
+    fromWindow("PhysilinksSceneRegistry", {});
 
-  const ui = window.PhysilinksUI.create();
+  const createUI = getFactory("PhysilinksUI");
+  const ui = createUI();
   const { sceneEl } = ui;
 
   let width = sceneEl.clientWidth;
   let height = sceneEl.clientHeight;
   const BALL_BASELINE = 680; // reference height used for relative ball sizing
 
+  const createEngine = getFactory("PhysilinksEngine");
   const { engine, render, runner, startRunner, stopRunner, setRenderSize } =
-    window.PhysilinksEngine.create({
+    createEngine({
       sceneEl,
       width,
       height,
@@ -64,13 +110,14 @@
     (getSceneById && getSceneById(scenes, initialSceneId)) || scenes[0] || null;
 
   if (currentScene && currentScene.config) {
-    Object.assign(config, currentScene.config);
-    config.link = { ...currentScene.config.link };
+    setConfigForScene(currentScene.config);
   }
 
   const rebuildSceneBodies = () => {
     boundaries.forEach((b) => World.remove(world, b));
-    boundaries = currentScene.createBodies(width, height);
+    const nextBoundaries = currentScene.createBodies(width, height);
+    boundaries.length = 0;
+    boundaries.push(...nextBoundaries);
     rotators = boundaries.filter((b) => b.plugin && b.plugin.rotSpeed);
     oscillators = boundaries.filter((b) => b.plugin && b.plugin.oscillate);
     World.add(world, boundaries);
@@ -91,12 +138,41 @@
   let spawnSystem = null;
   let input = null;
 
+  const storage = fromWindow("PhysilinksStorage", {});
   const {
     loadHighScore = () => 0,
     loadLongestChain = () => 0,
     saveHighScore = () => {},
     saveLongestChain = () => {},
-  } = window.PhysilinksStorage || {};
+  } = storage;
+
+  const resetEngineForScene = (
+    sceneConfig,
+    { prevRadius, timeScaleOverride, resetPlugins = true } = {},
+  ) => {
+    if (resetPlugins) {
+      world.plugin = world.plugin || {};
+      world.plugin.stormSteps = Array.isArray(sceneConfig?.spawnIntervals)
+        ? sceneConfig.spawnIntervals
+        : null;
+      world.plugin.squareOffset = 0;
+      engine.plugin = engine.plugin || {};
+      engine.plugin.stormState = null;
+    }
+    spawnSystem.updateBallRadius(prevRadius);
+    engine.gravity.scale =
+      typeof sceneConfig?.gravityScale === "number"
+        ? sceneConfig.gravityScale
+        : defaultGravityScale;
+    engine.gravity.x = 0;
+    engine.gravity.y = config.gravity;
+    engine.timing.timeScale =
+      typeof timeScaleOverride === "number"
+        ? timeScaleOverride
+        : typeof sceneConfig?.timeScale === "number"
+          ? sceneConfig.timeScale
+          : defaultTimeScale;
+  };
 
   const applyScene = (sceneId) => {
     const next = (getSceneById && getSceneById(scenes, sceneId)) || scenes[0];
@@ -105,50 +181,9 @@
     ui.setSceneSelection(next.id);
     setSceneIdInUrl(next.id);
     const prevRadius = config.ballRadius;
-    Object.assign(config, next.config);
-    config.link = { ...(next.config?.link || {}) };
-    const sceneMessages = next.config?.messages || {};
-    config.messages = {
-      durationMs: Number.isFinite(sceneMessages.durationMs)
-        ? sceneMessages.durationMs
-        : defaultMessageConfig.durationMs,
-      text:
-        typeof sceneMessages.text === "string" && sceneMessages.text.trim()
-          ? sceneMessages.text.trim()
-          : defaultMessageConfig.text,
-      position: {
-        xPercent:
-          typeof sceneMessages.position?.xPercent === "number"
-            ? sceneMessages.position.xPercent
-            : defaultMessageConfig.position.xPercent,
-        yPercent:
-          typeof sceneMessages.position?.yPercent === "number"
-            ? sceneMessages.position.yPercent
-            : defaultMessageConfig.position.yPercent,
-      },
-      colors: Array.isArray(sceneMessages.colors)
-        ? sceneMessages.colors
-        : defaultMessageConfig.colors,
-    };
+    setConfigForScene(next.config);
     ui.setMessageDefaults(config.messages);
-    world.plugin = world.plugin || {};
-    world.plugin.stormSteps = Array.isArray(next.config?.spawnIntervals)
-      ? next.config.spawnIntervals
-      : null;
-    world.plugin.squareOffset = 0;
-    engine.plugin = engine.plugin || {};
-    engine.plugin.stormState = null;
-    engine.gravity.scale =
-      typeof next.config.gravityScale === "number"
-        ? next.config.gravityScale
-        : defaultGravityScale;
-    engine.timing.timeScale =
-      typeof next.config.timeScale === "number"
-        ? next.config.timeScale
-        : defaultTimeScale;
-    spawnSystem.updateBallRadius(prevRadius);
-    engine.gravity.x = 0;
-    engine.gravity.y = config.gravity;
+    resetEngineForScene(next.config, { prevRadius });
     clearedCount = 0;
     levelWon = false;
     clearedByColor = {};
@@ -193,7 +228,8 @@
     ui.showGameOver(score);
   };
 
-  spawnSystem = window.PhysilinksSpawn.create({
+  const createSpawn = getFactory("PhysilinksSpawn");
+  spawnSystem = createSpawn({
     config,
     world,
     balls,
@@ -205,7 +241,8 @@
     isGameOver: () => gameOver,
     ballBaseline: BALL_BASELINE,
   });
-  const goals = window.PhysilinksGoals.create({
+  const createGoals = getFactory("PhysilinksGoals");
+  const goals = createGoals({
     config,
     getCurrentScene: () => currentScene,
     getScore: () => score,
@@ -245,13 +282,10 @@
     ui.hideGameOver();
     ui.hideWin();
     ui.setPauseState(false);
-    engine.gravity.scale =
-      typeof currentScene?.config?.gravityScale === "number"
-        ? currentScene.config.gravityScale
-        : defaultGravityScale;
-    engine.gravity.x = 0;
-    engine.gravity.y = config.gravity;
-    engine.timing.timeScale = 1;
+    resetEngineForScene(currentScene?.config || {}, {
+      timeScaleOverride: 1,
+      resetPlugins: false,
+    });
     startRunner();
     updateHud();
     if (isGridScene()) {
@@ -341,7 +375,10 @@
           remaining.push(b);
         }
       });
-      boundaries = remaining;
+      boundaries.length = 0;
+      boundaries.push(...remaining);
+      rotators = rotators.filter((b) => boundaries.includes(b));
+      oscillators = oscillators.filter((b) => boundaries.includes(b));
     }
   };
 
@@ -508,7 +545,8 @@
     goals.maybeAnnounceGoalProgress(goal);
   };
 
-  input = window.PhysilinksInput.create({
+  const createInput = getFactory("PhysilinksInput");
+  input = createInput({
     render,
     world,
     balls,