Смотри
+        final float backSpriteX = TEXTURE_WIDTH * 0.5f - backTextureRegion.getWidth() * 0.5f;
+        final float backSpriteY = TEXTURE_HEIGHT * 0.5f - backTextureRegion.getHeight() * 0.5f;
+
+        Sprite backSprite = new Sprite(backSpriteX
+                                        , backSpriteY
+                                        , backTextureRegion
+                                        , mEngine.getVertexBufferObjectManager());
можно заменить на 
final Point backSprite = new Point(TEXTURE_WIDTH * 0.5f - backTextureRegion.getWidth() * 0.5f
                                                   , TEXTURE_HEIGHT * 0.5f - backTextureRegion.getHeight() * 0.5f);
Sprite backSprite = new Sprite(backSprite
                                        , backTextureRegion
                                        , mEngine.getVertexBufferObjectManager());