				const ambientLight = new THREE.AmbientLight( 0x555555 );
				scene.add( ambientLight );

				// renderer

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				renderer.setAnimationLoop( animate );
				document.body.appendChild( renderer.domElement );

				stats = new Stats();
				document.body.appendChild( stats.dom );

				//

				const gui = new GUI();
				gui.add( params