diff --git a/js/GOSim.ts b/js/GOSim.ts
new file mode 100644
index 00000000..b117ba2d
--- /dev/null
+++ b/js/GOSim.ts
@@ -0,0 +1,52 @@
+// Copyright 2022, University of Colorado Boulder
+
+/**
+ * GOSim is the subclass of Sim used by both the 'full' and 'basics' versions of Geometric Optics.
+ *
+ * @author Chris Malley (PixelZoom, Inc.)
+ */
+
+import Sim from '../../joist/js/Sim.js';
+import merge from '../../phet-core/js/merge.js';
+import Tandem from '../../tandem/js/Tandem.js';
+import geometricOptics from './geometricOptics.js';
+import LensScreen from './lens/LensScreen.js';
+import MirrorScreen from './mirror/MirrorScreen.js';
+import GOConstants from './common/GOConstants.js';
+import { Node } from '../../scenery/js/imports.js';
+
+type GOSimOptions = {
+  isBasicsVersion?: boolean,
+  createOptionsDialogContent?: ( tandem: Tandem ) => Node
+};
+
+class GOSim extends Sim {
+
+  /**
+   * @param title
+   * @param providedOptions
+   */
+  constructor( title: string, providedOptions?: GOSimOptions ) {
+
+    const options = merge( {
+      credits: GOConstants.CREDITS,
+
+      // pdom options
+      hasKeyboardHelpContent: true
+    }, providedOptions );
+
+    super( title, [
+      new LensScreen( {
+        isBasicsVersion: options.isBasicsVersion,
+        tandem: Tandem.ROOT.createTandem( 'lensScreen' )
+      } ),
+      new MirrorScreen( {
+        isBasicsVersion: options.isBasicsVersion,
+        tandem: Tandem.ROOT.createTandem( 'mirrorScreen' )
+      } )
+    ], options );
+  }
+}
+
+geometricOptics.register( 'GOSim', GOSim );
+export default GOSim;
\ No newline at end of file
diff --git a/js/geometric-optics-main.ts b/js/geometric-optics-main.ts
index 3ba568b2..288ea544 100644
--- a/js/geometric-optics-main.ts
+++ b/js/geometric-optics-main.ts
@@ -3,36 +3,22 @@
 /**
  * Main entry point for the sim.
  *
- * @author Martin Veillette
  * @author Chris Malley (PixelZoom, Inc.)
  */
 
-import Sim from '../../joist/js/Sim.js';
 import simLauncher from '../../joist/js/simLauncher.js';
 import Tandem from '../../tandem/js/Tandem.js';
 import GOGlobalOptionsNode from './common/view/GOGlobalOptionsNode.js';
 import geometricOpticsStrings from './geometricOpticsStrings.js';
-import LensScreen from './lens/LensScreen.js';
-import MirrorScreen from './mirror/MirrorScreen.js';
-import GOConstants from './common/GOConstants.js';
-
-const simOptions = {
-
-  credits: GOConstants.CREDITS,
-
-  // Creates content for the Options dialog, accessible via the PhET menu
-  createOptionsDialogContent: ( tandem: Tandem ) => new GOGlobalOptionsNode( {
-    tandem: tandem
-  } ),
-
-  // pdom options
-  hasKeyboardHelpContent: true
-};
+import GOSim from './GOSim.js';
 
 simLauncher.launch( () => {
-  const sim = new Sim( geometricOpticsStrings[ 'geometric-optics' ].title, [
-    new LensScreen( { tandem: Tandem.ROOT.createTandem( 'lensScreen' ) } ),
-    new MirrorScreen( { tandem: Tandem.ROOT.createTandem( 'mirrorScreen' ) } )
-  ], simOptions );
+  const sim = new GOSim( geometricOpticsStrings[ 'geometric-optics' ].title, {
+
+    // Creates content for the Options dialog, accessible via the PhET menu
+    createOptionsDialogContent: ( tandem: Tandem ) => new GOGlobalOptionsNode( {
+      tandem: tandem
+    } )
+  } );
   sim.start();
 } );