SpriteKit increasing speed of move action

Question

I have a simple game that two lines moving from top to bottom of the screen. There is a fixed space between those two lines and a ball has to pass through in that space otherwise game is over.

I have no problem with the basics of the game, I can add two lines, a space which has different position every time but I also want to increase the moving speed of lines. I tried to use a timer and increase TimeInterval of SKAction.move but since lines which added later is faster, horizontal space between lines gets smaller which I don't want to happen.

This is the function that adds two lines and move them to bottom of the screen.

func addLines() {

    let lineNodeFirst = SKSpriteNode(color: .red, size: CGSize(width: random(min: 100, max: 400), height: 10.0))
    lineNodeFirst.position = CGPoint(x: -size.width / 2, y: 0 + size.height / 2 + 100)
    lineNodeFirst.anchorPoint = CGPoint.zero

    let actionMove = SKAction.move(to: CGPoint(x: lineNodeFirst.position.x, y: 0 - size.height / 2), duration: TimeInterval(2.3))
    let actionMoveDone = SKAction.removeFromParent()

    lineNodeFirst.run(SKAction.sequence([actionMove, actionMoveDone]))

    let centerPoint = CGPoint(x: lineNodeFirst.size.width / 2 - (lineNodeFirst.size.width * lineNodeFirst.anchorPoint.x), y: lineNodeFirst.size.height / 2 - (lineNodeFirst.size.height * lineNodeFirst.anchorPoint.y))
    lineNodeFirst.physicsBody = SKPhysicsBody(rectangleOf: lineNodeFirst.size, center: centerPoint)

    lineNodeFirst.physicsBody?.isDynamic = true
    lineNodeFirst.physicsBody?.categoryBitMask = 2
    lineNodeFirst.physicsBody?.contactTestBitMask = 1
    lineNodeFirst.physicsBody?.collisionBitMask = 0

    self.addChild(lineNodeFirst)

    let spaceBetweenNodes: CGFloat = 150
    let lineNodeSecondWidth: CGFloat = size.width - lineNodeFirst.size.width - spaceBetweenNodes

    let lineNodeSecond = SKSpriteNode(color: .red, size: CGSize(width: lineNodeSecondWidth, height: 10.0))
    lineNodeSecond.anchorPoint = CGPoint.zero
    let lineNodeSecondX = lineNodeFirst.position.x + lineNodeFirst.size.width + spaceBetweenNodes
    lineNodeSecond.position = CGPoint(x: lineNodeSecondX, y: lineNodeFirst.position.y)

    let actionMoveSecond = SKAction.move(to: CGPoint(x: lineNodeSecond.position.x, y: 0 - size.height / 2), duration: TimeInterval(2.3))

    lineNodeSecond.run(SKAction.sequence([actionMoveSecond, actionMoveDone]))

    let centerPointSecond = CGPoint(x: lineNodeSecond.size.width / 2 - (lineNodeSecond.size.width * lineNodeSecond.anchorPoint.x), y: lineNodeSecond.size.height / 2 - (lineNodeSecond.size.height * lineNodeSecond.anchorPoint.y))
    lineNodeSecond.physicsBody = SKPhysicsBody(rectangleOf: lineNodeSecond.size, center: centerPointSecond)

    lineNodeSecond.physicsBody?.isDynamic = true
    lineNodeSecond.physicsBody?.categoryBitMask = 2
    lineNodeSecond.physicsBody?.contactTestBitMask = 1
    lineNodeSecond.physicsBody?.collisionBitMask = 0

    self.addChild(lineNodeSecond)

}

I share a demo of my app which has the basics. Any suggestion for increasing move speed of lines?

Demo Video

SpriteKit increasing speed of move action

1 Answers