Playable Game Area in Swift 3.0 - swift

Question

I'm creating a mario clone for mac to help me learn swift programming. An issue I have come across is setting a playable game area. As of now, the 2 backgrounds I have ("background" and "level") will move when the left or right keys are pressed but grey areas at the sides will become visible. I want to be able to make the backgrounds move, but set an area at which they will stop moving.
import SpriteKit
class GameScene: SKScene {
let player = SKSpriteNode(imageNamed: "mario")
let background = SKSpriteNode(imageNamed: "background")
let level = SKSpriteNode(imageNamed: "level")
override func didMove(to view: SKView) {
/* Setup your scene here */
//self.physicsBody = SKPhysicsBody(edgeLoopFromRect: self.frame)
level.size = self.size
level.position = CGPoint(x: self.size.width/2, y: self.size.height/2)
level.zPosition = 1
self.addChild(level)
background.size = self.size
background.position = CGPoint(x: level.size.width + 511, y: self.size.height/2)
background.zPosition = 0
self.addChild(background)
player.setScale(0.23)
player.position = CGPoint(x: self.size.width/8, y: 120)
player.zPosition = 2
self.addChild(player)
}
override func keyDown(with theEvent: NSEvent) {
let keyCode = theEvent.keyCode
//Moving Right
if keyCode == 124 {
level.run(SKAction.sequence([SKAction.moveBy(x: -20, y: 0, duration: 0.2)]))
background.run(SKAction.sequence([SKAction.moveBy(x: -20, y: 0, duration: 0.2)]))
player.xScale = 0.23
}
//Moving Left
if keyCode == 123 {
background.run(SKAction.sequence([SKAction.moveBy(x: 20, y: 0, duration: 0.2)]))
level.run(SKAction.sequence([SKAction.moveBy(x: 20, y: 0, duration: 0.2)]))
player.xScale = -0.23
}
//Jump
if keyCode == 126{
player.run(SKAction.sequence([SKAction.moveTo(y: 250, duration: 0.15),SKAction.moveTo(y: 120, duration: 0.2)]))
}
}
}

Answer 1

I'm sure there is a much better, more clever solution, but off the top of my head you could add:
let LEFTBOUND: Int = //Insert the left limit here.
let RIGHTBOUND: Int = //Insert the right limit here.
Inside func keyDown(), in the moving right/left if-statements, nest these:
if level.position.x < RIGHTBOUND:
//Move level so long as it is less than the RIGHTBOUND value.
//TODO: set the level.position to RIGHTBOUND so it doesn't keep updating with new values while keyDown is true.
if level.position.x > LEFTBOUND:
//Move level so long as it is greater than the LEFTBOUND value.
//TODO: set the level.position to LEFTBOUND so it doesn't keep updating with new values while the keyDown is true.
//Repeat theses steps for background.position.x
You should also restrict the player movement so the player doesn't run out of the level unrecoverably.