leftSide.setName("left side");
leftSide.setNoFill(true); //Make it invisible -> only used for dragging
leftSide.setNoStroke(true);
leftSide.unregisterAllInputProcessors();
leftSide.removeAllGestureEventListeners(DragProcessor.class);
leftSide.registerInputProcessor(new DragProcessor(app));
leftSide.addGestureListener(DragProcessor.class, new GameFieldHalfDragListener(blueCircle));
physicsContainer.addChild(0, leftSide);
MTRectangle rightSide = new MTRectangle(
PhysicsHelper.scaleDown(app.width/2f, scale), PhysicsHelper.scaleDown(0, scale),
PhysicsHelper.scaleDown(app.width, scale), PhysicsHelper.scaleDown(app.height, scale)