Bit more cleanup

assets/entities/cube.js

@@ -1,14 +1,17 @@
 function CubeEntity() {
   Entity.call(this);
+
   this.add(POSITION);
+  this.add(MESH);
+  this.add(MATERIAL);
+  
   this.position.x = 0;
   this.position.y = 0;
   this.position.z = 0;
-  this.add(MESH);
-  this.add(MATERIAL);
 }
 
-Object.assign(CubeEntity.prototype, Entity.prototype);
+CubeEntity.prototype = Object.create(Entity.prototype);
+CubeEntity.prototype.constructor = CubeEntity;
 
 CubeEntity.prototype.update = function() {
   var speed = 3.0;