diff --git a/public/ioquake3/player.html b/public/ioquake3/player.html
index 6738117..afbd073 100644
--- a/public/ioquake3/player.html
+++ b/public/ioquake3/player.html
@@ -71,6 +71,7 @@
       const PAK_STORE = 'pk3-files';
       const SETTINGS_STORE = 'settings';
       const OPENARENA_KEY = 'openarena-enabled';
+      const PROJECT_CONFIG_KEY = 'q3edit.project.current.v1';
       const loading = document.getElementById('loading');
       const canvas = document.getElementById('canvas');
       const nativeGetContext = canvas.getContext.bind(canvas);
@@ -259,8 +260,35 @@
         return basename.replace(/[^a-zA-Z0-9._-]/g, '_');
       }
 
+      function safeGameDirectory(name) {
+        const candidate = String(name || '').trim();
+        return /^[a-zA-Z0-9_-]+$/.test(candidate) ? candidate : 'baseq3';
+      }
+
+      function loadProjectGameDirectory() {
+        try {
+          const project = JSON.parse(localStorage.getItem(PROJECT_CONFIG_KEY) || 'null');
+          return project?.game?.gameDirectory;
+        } catch {
+          return null;
+        }
+      }
+
       async function loadLaunchAssets(launch) {
         const stored = await loadStoredConfiguration();
+        const configuredGameDir = safeGameDirectory(launch.gameDirectory);
+
+        // Standalone games provide their own default.cfg and game VMs. Mount
+        // their archives under the configured base game directory so ioquake3
+        // does not validate a custom pak0.pk3 as retail baseq3 data.
+        if (configuredGameDir !== 'baseq3' && configuredGameDir !== 'baseoa') {
+          if (stored.archives.length === 0) {
+            throw new Error(`No PK3 files are enabled for ${configuredGameDir}. Add the game's base archive in the editor.`);
+          }
+          const archives = [...stored.archives];
+          if (launch.packagePk3) archives.push({ name: `${launch.mapName}.pk3`, data: launch.packagePk3 });
+          return { archives, gameDir: configuredGameDir };
+        }
 
         // A retail pak0 and OpenArena's pak0 have the same filename. Mixing the
         // two would overwrite one of them in the virtual filesystem and launch
@@ -317,6 +345,20 @@
           const assets = await loadLaunchAssets(launch);
           setStatus('Loading ioquake3 WebAssembly runtime…');
           const ioquake3 = (await import('./ioquake3.js')).default;
+          const renderWidth = Math.max(640, Math.floor(canvas.clientWidth || window.innerWidth));
+          const renderHeight = Math.max(480, Math.floor(canvas.clientHeight || window.innerHeight));
+          canvas.width = renderWidth;
+          canvas.height = renderHeight;
+          const standaloneGame = assets.gameDir !== 'baseq3' && assets.gameDir !== 'baseoa';
+          const standaloneRendererArguments = standaloneGame
+            ? [
+                '+set', 'r_ext_framebuffer_object', '0',
+                '+set', 'r_hdr', '0',
+                '+set', 'r_postProcess', '0',
+                '+set', 'r_overBrightBits', '0',
+                '+set', 'r_mapOverBrightBits', '0',
+              ]
+            : [];
           const availableBotNames = assets.gameDir === 'baseoa'
             ? ['Sarge', 'Grism', 'Sorceress']
             : ['Sarge', 'Major', 'Grunt'];
@@ -330,9 +372,15 @@
               '+set', 'sv_pure', '0',
               '+set', 'net_enabled', '0',
               '+set', 'con_notifytime', '0',
-              '+set', 'r_mode', '-2',
+              '+set', 'r_customwidth', String(renderWidth),
+              '+set', 'r_customheight', String(renderHeight),
+              '+set', 'r_mode', '-1',
               '+set', 'r_fullscreen', '0',
-              '+set', 'r_allowResize', '1',
+              // Standalone renderers may not recover cleanly from ioquake3's
+              // automatic vid_restart. Keep their framebuffer stable and let
+              // CSS scale the canvas when the preview or browser is resized.
+              '+set', 'r_allowResize', standaloneGame ? '0' : '1',
+              ...standaloneRendererArguments,
               ...(launch.noclip ? ['+set', 'sv_cheats', '1'] : []),
               ...(launch.botCount > 0 ? [
                 '+set', 'bot_enable', '1',
@@ -418,7 +466,10 @@
           Array.isArray(command.args) && command.args.every(argument => typeof argument === 'string')
         ) : [];
         const packagePk3 = event.data.packagePk3 instanceof ArrayBuffer ? event.data.packagePk3 : null;
-        void start({ mapName, bsp, aas, packagePk3, botCount, botSkill, noclip: event.data.noclip === true, commands });
+        // Reading the stored project is also a compatibility fallback for an
+        // editor tab that was already open when the player shell was updated.
+        const gameDirectory = safeGameDirectory(event.data.gameDirectory ?? loadProjectGameDirectory());
+        void start({ mapName, gameDirectory, bsp, aas, packagePk3, botCount, botSkill, noclip: event.data.noclip === true, commands });
       });
 
       window.addEventListener('error', (event) => fail(event.error ?? event.message));
diff --git a/src/project-config.ts b/src/project-config.ts
index ab60515..2fec0ca 100644
--- a/src/project-config.ts
+++ b/src/project-config.ts
@@ -48,6 +48,11 @@ const strings = (value: unknown): string[] => Array.isArray(value)
   : [];
 const text = (value: unknown, fallback = ''): string => typeof value === 'string' ? value : fallback;
 
+export function normalizeGameDirectory(value: unknown, fallback = 'baseq3'): string {
+  const candidate = text(value).trim();
+  return /^[a-zA-Z0-9_-]+$/.test(candidate) ? candidate : fallback;
+}
+
 export function normalizeProjectConfiguration(value: unknown): ProjectConfiguration {
   const result = structuredClone(DEFAULT_PROJECT_CONFIGURATION);
   if (!isRecord(value)) return result;
@@ -59,7 +64,9 @@ export function normalizeProjectConfiguration(value: unknown): ProjectConfigurat
   const overrides = isRecord(value.overrides) ? value.overrides : {};
   result.name = text(value.name, result.name).slice(0, 120);
   result.game = {
-    basePath: text(game.basePath), gameDirectory: text(game.gameDirectory, result.game.gameDirectory), executable: text(game.executable),
+    basePath: text(game.basePath),
+    gameDirectory: normalizeGameDirectory(game.gameDirectory, result.game.gameDirectory),
+    executable: text(game.executable),
   };
   result.assets = {
     archives: strings(assets.archives), searchPaths: strings(assets.searchPaths),
diff --git a/src/ui.ts b/src/ui.ts
index a9d37cd..cdce96e 100644
--- a/src/ui.ts
+++ b/src/ui.ts
@@ -67,6 +67,7 @@ export interface AssetLoadingHandle {
 
 interface GamePreviewLaunch {
   mapName: string;
+  gameDirectory: string;
   bsp: Uint8Array;
   aas: Uint8Array | null;
   botCount: number;
@@ -2319,7 +2320,9 @@ export class UI {
     const packageCopy = packagePk3 ? new Uint8Array(packagePk3) : null;
     const retainedPackage = packagePk3 ? new Uint8Array(packagePk3) : null;
     this.gamePreviewLaunch = {
-      mapName: safeMapName, bsp: retainedBsp, aas: retainedAas,
+      mapName: safeMapName,
+      gameDirectory: this.editor.projectConfiguration.game.gameDirectory,
+      bsp: retainedBsp, aas: retainedAas,
       botCount, botSkill, noclip, commands: structuredClone(commands),
       packagePk3: retainedPackage,
     };
@@ -2371,7 +2374,6 @@ export class UI {
     frame.title = `ioquake3 preview of ${safeMapName}`;
     frame.src = '/ioquake3/player.html';
     frame.allow = 'autoplay; fullscreen';
-    frame.setAttribute('allowfullscreen', '');
 
     const actions = document.createElement('div');
     actions.className = 'editor-dialog-actions game-preview-actions';
@@ -2401,6 +2403,7 @@ export class UI {
         const launchMessage = {
           type: 'q3edit-player:launch',
           mapName: safeMapName,
+          gameDirectory: this.gamePreviewLaunch?.gameDirectory ?? 'baseq3',
           bsp: bspCopy.buffer,
           aas: aasCopy?.buffer ?? null,
           botCount,
diff --git a/tests/project-config.test.ts b/tests/project-config.test.ts
index b131678..109b821 100644
--- a/tests/project-config.test.ts
+++ b/tests/project-config.test.ts
@@ -5,6 +5,7 @@ import {
   PROJECT_CONFIG_STORAGE_KEY,
   importProjectConfiguration,
   loadProjectConfiguration,
+  normalizeGameDirectory,
   resolveProjectPreferences,
   saveProjectConfiguration,
 } from '../src/project-config';
@@ -48,4 +49,11 @@ describe('project configuration', () => {
   it('rejects imports from unsupported future versions', () => {
     expect(() => importProjectConfiguration('{"version":2}')).toThrow('newer than this editor supports');
   });
+
+  it('accepts safe standalone game directories and rejects filesystem paths', () => {
+    expect(normalizeGameDirectory('tinygame')).toBe('tinygame');
+    expect(normalizeGameDirectory('my-game_2')).toBe('my-game_2');
+    expect(normalizeGameDirectory('../baseq3')).toBe('baseq3');
+    expect(normalizeGameDirectory('mods/tinygame')).toBe('baseq3');
+  });
 });