当按下屏幕时，使用以下代码创建的球:varn=1funcaddBall(_x:CGFloat){letnumShape=SKShapeNode(circleOfRadius:30)numShape.name="ball"numShape.position=CGPoint(x:x,y:frame.maxY-40)numShape.physicsBody=SKPhysicsBody(circleOfRadius:30)numShape.fillColor=SKColor.whitenumShape.physicsBody?.density=0.1numShape.physicsBody?.