A swift playground that modifies the black and white demo to be more flexible and maintainable

CCMagentaCyanTunnel.swift

import SpriteKit
import PlaygroundSupport

// Variables to manipulate the demo
let COLORS: [UIColor] = [.white, .cyan, .white, .magenta]
let NUM_SHAPES = 6 // The number of shapes that will appear onscreen
let SPEED = 0.5 // the speed at whic the demo will move

/*
// a linear scaling function
func getScaleFactor(index: Int) -> Double {
    return 100.0 / Double(NUM_SHAPES) * Double(index)
}
 */

let totalSize = (pow(Double(NUM_SHAPES), 2) + Double(NUM_SHAPES)) / 2
func getScaleFactor(index: Int) -> Double {
    var size = 0
    for i in 0 ... index {
        size += i
    }
    return 100.0 * Double(size) / totalSize
}

func getScaleAction(from: Int, to: Int, wait: Int = 0) -> SKAction {
    let waitDuration = Double(SPEED) * Double(wait)
    let scaleDuration = Double(SPEED) * Double(to - from)
    
    let initialScaleFactor = getScaleFactor(index: from)
    let finalScaleFactor = getScaleFactor(index: to)
    
    let wait = SKAction.wait(forDuration: waitDuration)
    let initialScale = SKAction.scale(to: CGFloat(initialScaleFactor), duration: 0.0)
    let finalScale = SKAction.scale(to: CGFloat(finalScaleFactor), duration: scaleDuration)
    
    return SKAction.sequence([
        initialScale,
        wait,
        finalScale
    ])
    
}

func createShape(color: UIColor) -> SKShapeNode {
    let shape = SKShapeNode(rect: CGRect(x: -0.005, y: -0.005, width: 0.01, height: 0.01))
    shape.lineWidth = 0
    shape.fillColor = color
    shape.position = CGPoint(x: 0.5, y: 0.5)
    return shape
}

let shapes = SKNode()
for i in (0...NUM_SHAPES).reversed() {
    
    // INITIALIZATION 
    let colorIndex = shapes.children.count % COLORS.count
    let color = COLORS[colorIndex]
    let shape = createShape(color: color)
    
    let initialScaleFactor = getScaleFactor(index: i)
    let initialScale = SKAction.scale(to: CGFloat(initialScaleFactor), duration: 0)
    shape.run(initialScale)
    
    // LOOP
    let scale = getScaleAction(from: i, to: i + COLORS.count)
    shape.run(SKAction.repeatForever(scale))
    shapes.addChild(shape)
}

for i in (1...COLORS.count - 1) {
    
    // INITIALIZATION
    let colorIndex = shapes.children.count % COLORS.count
    let color = COLORS[colorIndex]
    
    let shape = createShape(color: color)
    
    let initialScaleFactor = 0
    let initialScale = SKAction.scale(to: CGFloat(initialScaleFactor), duration: 0)
    shape.run(initialScale)
    
    // LOOP
    let scale = getScaleAction(from: 0, to: COLORS.count - i, wait: i)
    shape.run(SKAction.repeatForever(scale))
    shapes.addChild(shape)
}

let view = SKView(frame: CGRect(x: 0.0, y: 0.0, width: 1000, height: 1000))

let scene = SKScene()
scene.scaleMode = .aspectFit
scene.backgroundColor = #colorLiteral(red: 0.807843137254902, green: 0.027450980392156862, blue: 0.3333333333333333, alpha: 1.0)

scene.addChild(shapes)
view.presentScene(scene)
PlaygroundPage.current.liveView = view