public boolean isPositionValid(){
		//check overlapping with walls
		for(Wall wall : Game.gameField.getWalls()){
			if(wall.overlaps(center))
				return false;
		}
		//check overlapping with other balls
		for(Ball ball : Game.gameField.getBalls()){
			if(ball == this)
				continue;
			if(ball.getCenterPoint().distance(center) < RADIUS * 2)
				return false;
		}
		return GameField.FIELD.contains(center);
	}