将节点保留在后台

Question

我在一个项目上工作，我在后台生成随机圆圈，这样我就可以让它们消失并让它们消失并一遍又一遍地完成这个过程（对于一个旅行效果）但是当我这样做时，圆圈会重叠我所有其他节点。 是否可以将它们保留在背景中？

我使用此代码生成我的圈子

let spawn = SKAction.runBlock({() in self.TripEffects()})
        let delay = SKAction.waitForDuration(1)
        let sequense = SKAction.sequence([spawn, delay])
        let Loop = SKAction.repeatActionForever(sequense)
        self.runAction(Loop)


func TripEffects() {
    // Create Random RGB color
        var red = Float(arc4random_uniform(100)+1)
        red = red / 100
        var green = Float(arc4random_uniform(100)+1)
        green = green / 100
        var blue = Float(arc4random_uniform(100)+1)
        blue = blue / 100
    //define a circle
    let TripCircle = SKShapeNode(circleOfRadius: 1)
    //set the colors
    TripCircle.fillColor = SKColor( red:   CGFloat(red),green: CGFloat(green),
                                    blue:  CGFloat(blue),alpha: 1)
    //set the posiotion
    TripCircle.position = CGPoint (x: CGFloat(arc4random()%(canvasWidth)),
                                    y: CGFloat(arc4random()%(canvasHeight)))
    // add the node to the scene
        self.addChild(TripCircle)

     //set the Animation
    let Grow = SKAction.scaleTo(100, duration: 10)
    let Hide = SKAction.fadeAlphaTo(0, duration: 1)
    let Remove = SKAction.removeFromParent()
    let Sequence = SKAction.sequence([Grow, Hide, Remove])

     TripCircle.runAction(Sequence)
 }