diff --git a/html/index.html b/html/index.html
index 8b2a8a6..a7b7ab3 100644
--- a/html/index.html
+++ b/html/index.html
@@ -79,6 +79,7 @@
     <script src="js/render/atlas.js"></script>
     <script src="js/render/skins.js"></script>
     <script src="js/render/charSprites.js"></script>
+    <script src="js/render/packRegistry.js"></script>
     <script src="js/render/assetPacks.js"></script>
     <script src="js/render/renderModes.js"></script>
     <script src="js/render/charCustomize.js"></script>
diff --git a/html/js/render/assetPacks.js b/html/js/render/assetPacks.js
index cdc7085..1b75a4b 100644
--- a/html/js/render/assetPacks.js
+++ b/html/js/render/assetPacks.js
@@ -165,7 +165,14 @@
     };
     RK.activeThemeId = 'roguelike-interior';
 
-    RK.theme = function (id) { return RK.THEMES[id || RK.activeThemeId] || null; };
+    RK.theme = function (id) {
+        // With no explicit id, use the active topdown pack (registry-selected + entitlement-gated).
+        if (!id && RK.activePackId) {
+            var ap = RK.activePackId('topdown');
+            if (ap && RK.THEMES[ap]) return RK.THEMES[ap];
+        }
+        return RK.THEMES[id || RK.activeThemeId] || null;
+    };
 
     // Effective tile map = theme defaults merged with localStorage overrides from the picker.
     RK.tileMap = function (id) {
@@ -305,6 +312,19 @@
         }
     };
 
+    // Register the built-in RENDER packs in the pack registry (packRegistry.js) so iso/3D become
+    // multi-pack like topdown themes already are. Each maps to its catalog id; the active pack per
+    // projection is entitlement-gated + user-selectable. Adding a pack later = registerPack(...) +
+    // assets + a catalog row. Backward-compatible: one pack per projection resolves to these.
+    if (RK.registerPack) {
+        RK.registerPack({ id: 'roguelike-interior', label: 'Roguelike Interior', projection: 'topdown', kind: 'tiles', assets: RK.THEMES['roguelike-interior'] });
+        RK.registerPack({ id: 'iso-dungeon', label: 'Isometric Dungeon', projection: 'iso', kind: 'tiles', assets: RK.isoAssets });
+        RK.registerPack({ id: 'kenney-3d-characters', label: 'Animated 3D', projection: '3d', kind: 'skin', assets: RK.threeAssets });
+    }
+    // Active-pack resolvers the renderers read (fall back to the single default if the registry is absent).
+    RK.activeIsoAssets = function () { return (RK.activePackAssets && RK.activePackAssets('iso')) || RK.isoAssets; };
+    RK.activeThreeAssets = function () { return (RK.activePackAssets && RK.activePackAssets('3d')) || RK.threeAssets; };
+
     RK.packForProjection = function (projection) {
         for (var id in RK.PACKS) {
             if (RK.PACKS[id].projection === projection) return RK.PACKS[id];
diff --git a/html/js/render/avatarVisuals.js b/html/js/render/avatarVisuals.js
index 62ec551..3607dce 100644
--- a/html/js/render/avatarVisuals.js
+++ b/html/js/render/avatarVisuals.js
@@ -73,13 +73,13 @@
     }
 
     function isoCharacterFor(appearance) {
-        var assets = RK.isoAssets || {};
+        var assets = (RK.activeIsoAssets && RK.activeIsoAssets()) || RK.isoAssets || {};
         var chars = assets.characters || {};
         return chars[appearance.avatar] || chars.fallback || assets.character || null;
     }
 
     function modelFor(appearance) {
-        var assets = RK.threeAssets || {};
+        var assets = (RK.activeThreeAssets && RK.activeThreeAssets()) || RK.threeAssets || {};
         var models = assets.models || {};
         return models[appearance.avatar] || models.fallback || null;
     }
diff --git a/html/js/render/isoRenderer.js b/html/js/render/isoRenderer.js
index 398c502..12823fc 100644
--- a/html/js/render/isoRenderer.js
+++ b/html/js/render/isoRenderer.js
@@ -7,7 +7,7 @@
         opts = opts || {};
         this.name = 'iso';
         this.host = host;
-        this.assets = (root.RK && RK.isoAssets) || {};
+        this.assets = (root.RK && ((RK.activeIsoAssets && RK.activeIsoAssets()) || RK.isoAssets)) || {};
         this.tileW = opts.tileW || (this.assets.tile && this.assets.tile.w) || 84;
         this.tileH = opts.tileH || (this.assets.tile && this.assets.tile.h) || 42;
         this.imageW = opts.imageW || (this.assets.tile && this.assets.tile.imageW) || 92;
diff --git a/html/js/render/packRegistry.js b/html/js/render/packRegistry.js
new file mode 100644
index 0000000..86d55c3
--- /dev/null
+++ b/html/js/render/packRegistry.js
@@ -0,0 +1,75 @@
+// Pack registry — the engine behind "add more 2D tilesets / iso packs / 3D skins as products".
+//
+// A PACK is a rich, self-contained render environment for a projection (topdown | iso | 3d). Because
+// every scene (tavern OR dungeon) is kind-based (floor/wall/table/torch/monster…), the SAME pack
+// renders both — packs are interchangeable across town and dungeon. Each pack maps 1:1 to a catalog
+// entry (id/tier/threshold), so it's a monetizable product gated by entitlements.
+//
+// This module makes packs MULTI (like RK.THEMES already is for topdown) and adds active-pack
+// selection per projection. Renderers ask for the active pack's assets; a picker lets an unlocked
+// user switch. Adding a pack then = register(def) + drop assets + a catalog row.
+(function (root) {
+    'use strict';
+    var RK = root.RK = root.RK || {};
+
+    // id -> { id, label, projection: 'topdown'|'iso'|'3d', kind, assets }
+    // `assets` is the render-kit payload for that projection (theme tiles / iso set / 3d models).
+    RK.PACK_REGISTRY = RK.PACK_REGISTRY || {};
+
+    // Storage: localStorage in the browser, an in-memory map under Node/tests.
+    var mem = {};
+    function store() {
+        try { if (root.localStorage) return root.localStorage; } catch (_) {}
+        return { getItem: function (k) { return k in mem ? mem[k] : null; }, setItem: function (k, v) { mem[k] = String(v); } };
+    }
+    function key(projection) { return 'rk_pack_' + projection; }
+
+    RK.registerPack = function (def) {
+        if (!def || !def.id || !def.projection) return null;
+        RK.PACK_REGISTRY[def.id] = def;
+        return def;
+    };
+    RK.getPackDef = function (id) { return (id && RK.PACK_REGISTRY[id]) || null; };
+
+    RK.packsForProjection = function (projection) {
+        var out = [];
+        for (var id in RK.PACK_REGISTRY) {
+            if (RK.PACK_REGISTRY[id].projection === projection) out.push(RK.PACK_REGISTRY[id]);
+        }
+        return out;
+    };
+
+    // Packs the user can actually use for a projection (free ones + entitlement-unlocked ones).
+    RK.unlockedPacks = function (projection) {
+        return RK.packsForProjection(projection).filter(function (p) {
+            return !RK.canUsePack || RK.canUsePack(p.id);
+        });
+    };
+
+    // The user's chosen pack if it's registered for this projection AND unlocked; otherwise the
+    // first unlocked pack; otherwise null.
+    RK.activePackId = function (projection) {
+        var saved = store().getItem(key(projection));
+        var def = saved && RK.PACK_REGISTRY[saved];
+        if (def && def.projection === projection && (!RK.canUsePack || RK.canUsePack(saved))) return saved;
+        var unlocked = RK.unlockedPacks(projection);
+        return unlocked.length ? unlocked[0].id : null;
+    };
+
+    RK.activePack = function (projection) { return RK.getPackDef(RK.activePackId(projection)); };
+    RK.activePackAssets = function (projection) {
+        var def = RK.activePack(projection);
+        return def ? def.assets : null;
+    };
+
+    // Select a pack (persisted per projection). Refused if unregistered or locked. Returns success.
+    RK.setActivePack = function (id) {
+        var def = RK.getPackDef(id);
+        if (!def) return false;
+        if (RK.canUsePack && !RK.canUsePack(id)) return false;
+        store().setItem(key(def.projection), id);
+        return true;
+    };
+
+    if (typeof module !== 'undefined' && module.exports) module.exports = RK;
+})(typeof window !== 'undefined' ? window : this);
diff --git a/html/tavern.html b/html/tavern.html
index 95bc17c..80acccb 100644
--- a/html/tavern.html
+++ b/html/tavern.html
@@ -15,6 +15,7 @@
     <script src="js/render/charSprites.js"></script>
     <script src="js/render/catSprites.js"></script>
     <script src="js/render/zoomControl.js"></script>
+    <script src="js/render/packRegistry.js"></script>
     <script src="js/render/assetPacks.js"></script>
     <script src="js/render/avatarVisuals.js"></script>
     <script src="js/render/designedRoom.js"></script>
diff --git a/test/packRegistry_ultra.test.js b/test/packRegistry_ultra.test.js
new file mode 100644
index 0000000..e86be16
--- /dev/null
+++ b/test/packRegistry_ultra.test.js
@@ -0,0 +1,50 @@
+/**
+ * Pack registry — the engine for multi-pack, interchangeable render environments (products).
+ */
+describe('pack registry', () => {
+    let RK;
+    beforeEach(() => { jest.resetModules(); RK = require('../html/js/render/packRegistry'); });
+
+    function seed() {
+        RK.registerPack({ id: 'topA', label: 'A', projection: 'topdown', assets: { a: 1 } });
+        RK.registerPack({ id: 'isoFree', label: 'IsoFree', projection: 'iso', assets: { i: 1 } });
+        RK.registerPack({ id: 'isoPrem', label: 'IsoPrem', projection: 'iso', assets: { i: 2 } });
+    }
+
+    test('registers packs and lists them by projection', () => {
+        seed();
+        expect(RK.packsForProjection('iso').map(p => p.id).sort()).toEqual(['isoFree', 'isoPrem']);
+        expect(RK.getPackDef('topA').assets).toEqual({ a: 1 });
+        expect(RK.registerPack({ id: 'x' })).toBeNull(); // no projection -> rejected
+    });
+
+    test('unlockedPacks filters by canUsePack', () => {
+        seed();
+        RK.canUsePack = (id) => id !== 'isoPrem';
+        expect(RK.unlockedPacks('iso').map(p => p.id)).toEqual(['isoFree']);
+    });
+
+    test('active pack = saved-if-unlocked, else first unlocked; assets resolve', () => {
+        seed();
+        RK.canUsePack = () => true;
+        expect(RK.activePackId('iso')).toBe('isoFree');       // default = first unlocked
+        expect(RK.setActivePack('isoPrem')).toBe(true);
+        expect(RK.activePackId('iso')).toBe('isoPrem');       // saved choice sticks
+        expect(RK.activePackAssets('iso')).toEqual({ i: 2 });
+    });
+
+    test('a saved pack that later locks falls back; setActivePack refuses a locked pack', () => {
+        seed();
+        RK.canUsePack = () => true;
+        RK.setActivePack('isoPrem');
+        RK.canUsePack = (id) => id !== 'isoPrem';             // access lost
+        expect(RK.activePackId('iso')).toBe('isoFree');       // graceful fallback
+        expect(RK.setActivePack('isoPrem')).toBe(false);      // refused
+    });
+
+    test('a projection with no packs resolves to null', () => {
+        seed();
+        expect(RK.activePackId('3d')).toBeNull();
+        expect(RK.activePackAssets('3d')).toBeNull();
+    });
+});