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Move on with this tutorial!

Move on with this tutorial!

June 8, 2015

We'll need three Swift classes for our game right now:

  1. MainScene.swift
  2. Character.swift
  3. Piece.swift

MainScene.swift has already been created for us by SpriteBuilder so only need to create two.

If you haven't already, open up SushiNeko.xcodeproj, which you can do by going to File > Open Project In Xcode, or by navigating to it in Finder -- it should be in your SushiNeko.spritebuilder folder.

In Xcode, go to File > New > File. Select iOS Source from the left side and then Swift File. Press Next and save it as Character in your Source folder.

Now, define the Character class as a subclass of CCSprite in the newly created file.

It should look like this:

  class Character: CCSprite {


Follow the same steps to create Piece.swift and define the Piece class as a subclass of CCNode in the newly create file.

It should look like this:

  class Piece: CCNode {


Testing the project

You should now be able to run the project in Xcode. If you had tried earlier it would have crashed as soon as it launched because it could not find the Character and Piece classes.

Hit the run button to try it out. You should launch to the MainScene we created in SpriteBuilder. Nothing will work yet and there will be a few complaints in the console output but it should launch without crashing.

Its time to start filling in our code!

What's next

We'll be building the game's code piece by piece. Our plan is to:

  1. Build the sushi tower of obstacles
  2. Add touch controls to move the character
  3. Randomize the obstacle side
  4. Move down the sushi tower with every touch
  5. Detect collisions & trigger a game over
  6. Get the timer working
  7. Update the score

Building the Sushi Tower

We'll build the sushi tower up in the didLoadFromCCB method so that it's added before MainScene is shown to the player.

Our goal is to create a tower ten pieces high. When we start moving that tower down, we'll actually move the bottom piece back to the top of the tower instead of removing it from the scene. This will save a bit of processing power since we are reusing the same objects.

Start off by defining didLoadFromCCB.

It should look like:

  func didLoadFromCCB() {


We'll also need access to one of those code connections we added in SpriteBuilder.

Add an instance variable to MainScene for piecesNode. You should also create an empty Piece array called pieces.

After the opening curly brace in class MainScene: CCNode { add:

  weak var piecesNode: CCNode!
  var pieces: [Piece] = []

Remember, we always use implicitly unwrapped optionals (the !) for code connections from SpriteBuilder.

Inside the didLoadFromCCB method, load in ten instances of Piece.ccb and position them so they build up a tower. Add each piece as a child of piecesNode and use the contentSizeInPoints of the piece to calculate the offset in its y-position. Ten instances of Piece.ccb should be enough to cover the screen of any device you build on.

Give it a shot then run the project to see if your solution worked.

One possible way to write didLoadFromCCB is:

  for i in 0..<10 {
      let piece = CCBReader.load("Piece") as! Piece

      let yPos = piece.contentSizeInPoints.height * CGFloat(i)
      piece.position = CGPoint(x: 0, y: yPos)

In each iteration of the for-loop we load in a new Piece from Piece.ccb. We then set its x-position to 0 and y-position is set to the iteration number multiplied by piece.contentSizeInPoints.

Remember how we manually changed the anchor point and content size of the root node in Piece.ccb? Now you may be able to see how those values are making our life a whole lot easier on the code side. The lowest piece is added as a child of piecesNode with a position of (0, 0) and its exactly where we want it. Each subsequent piece is offset appropriately in the y-direction so they line up into a nice tower.

If your solution is different, make sure it matches the requirements above.

Your game should now look like this when you run it:

Once you have it working, move onto adding touch controls.

Add Touch Controls

To add touch controls we first need a method we can call to move the Character to the right side of the screen and back. We'll be relying on a little trick to make this easy -- setting the scaleX to -1 flips a sprite horizontally around its anchor point. Since Character already has an anchor point at the center of the screen, we can us this trick to flip it to the other side.

Your job is to create two methods in Character.swift:

  1. left - move the character to the left side of the screen
  2. right - move the character to the right side of the screen

We'll trigger these methods from MainScene when we add in the touch controls.

You should have added the following methods to the Character class:

  func left() {
      scaleX = 1

  func right() {
      scaleX = -1

Before we can actually detect touches, we need to complete the code connection for character and set userInteractionEnabled in the MainScene class.

Add this near where you declared the other instance variables:

  weak var character: Character!

Code connection variables should use the keyword weak because they only mark a reference to rather than an ownership of the object they are pointing to.

Add this to the end of didLoadFromCCB in MainScene.swift:

  userInteractionEnabled = true

Now we can override touchBegan and add in our code.

Create and empty touchBegan method in MainScene.swift:

  override func touchBegan(touch: CCTouch!, withEvent event: CCTouchEvent!) {


Inside touchBegan, try using touch.locationInWorld().x and CCDirector.sharedDirector().viewSize().width to determine which side of the screen a touch is on. Call character.left() and character.right() to trigger the correct movements.

The touchBegan method should look like:

  var xTouch = touch.locationInWorld().x
  var screenHalf = CCDirector.sharedDirector().viewSize().width / 2
  if xTouch < screenHalf {
  } else {

You should now be able to move the character from one side to another and back:

Randomize Each Obstacle's Side

Before we start randomizing the obstacle side, we should declare an enum to add uniformity to checking sides in code.

At the top of MainScene.swift (before the class declaration) add:

  enum Side {
      case Left, Right, None

Now we can refer to the type Side with three different values: Left, Right, and None. This will make our lives a lot easier throughout our code.

Let's set up the Piece class. We need to complete the code connections to left and right (our chopstick sprites from SpriteBuilder) and add a side variable to keep track of which obstacle is showing. We want this variable to trigger the correct visibility of left and right each time it changes.

Open up Piece.swift and add this to the top of the class declaration:

  weak var left: CCSprite!
  weak var right: CCSprite!

  var side: Side = .None {
      didSet {
          left.visible = false
          right.visible = false
          if side == .Right {
              right.visible = true
          } else if side == .Left {
              left.visible = true

The didSet property observer gets called each time the side variable is set. This allows us to trigger the correct visibility of left and right.

We want our obstacles (chopsticks) to randomly choose a side but we need to have a few rules to make sure the game is fair and we do not produce an impossible to pass sequence. Our rules for obstacle generation are:

  1. a piece has no obstacle if the previous piece had one
  2. right should appear 45% of the time an obstacle can be added
  3. left should appear 45% of the time an obstacle can be added
  4. no obstacle should appear 10% of the time an obstacle can be added

To make sure our pieces follow these rules, we'll pass in the obstacle side of the previous piece every time we randomize a piece. Time to implement the rules!

Create a method in the Piece class as follows:

  func setObstacle(lastSide: Side) -> Side {


Now fill it in according to our four rules. Remember to return the side that is randomly chosen.

You can call CCRANDOM_0_1() to randomly generate a number between 0 and 1.

The body of setObstacle should look like:

  if lastSide != .None {
      side = .None
  } else {
      let rand = CCRANDOM_0_1()
      if rand < 0.45 {
          side = .Left
      } else if rand < 0.9 {
          side = .Right
      } else {
          side = .None
  return side

The Piece class is all ready so let's go back to MainScene.swift. We need an instance variable lastPieceSide to keep track of the last piece's side. This will be especially important when we start moving the sushi tower down with each tap.

Add this near your other instance variables in MainScene:

  var pieceLastSide: Side = .Left

We're setting pieceLastSide to Left so that the bottom piece always has a side of None.

Add this below the line with var piece: Piece = CCBReader.load("Piece") as! Piece in didLoadFromCCB:

  pieceLastSide = piece.setObstacle(pieceLastSide)

This line is pretty powerful. It both randomizes the current piece's obstacle side and updates pieceLastSide since we return the chosen side.

Run the game. It should have randomized obstacles now!

Move the Sushi Tower

Our next goal is to get the sushi tower to move downward with each of the player's taps. Once we get that working we'll be able to add in collision detection!

Early we mentioned that we want the tower to cycle between the ten pieces we have already created. We want to create a stepTower method in the MainScene class that does the following:

  1. moves current piece to top of tower
  2. increase its zOrder by one
  3. randomize its obstacle
  4. moves piecesNode down by the content size of a piece

We'll add more to the stepTower method later on but go ahead and give this version a shot. Remember that you have a pieces array. You'll probably want to also create a new index variable, pieceIndex, to track the index of the current piece in pieces.

Do not rely on piecesNode.children. The order of this array is not guaranteed. It is currently optimized for drawing the contents to the screen but could change in the future.

You should have added a method like this to the MainScene class:

  func stepTower() {
      let piece = pieces[pieceIndex]

      let yDiff = piece.contentSize.height * 10
      piece.position = ccpAdd(piece.position, CGPoint(x: 0, y: yDiff))

      piece.zOrder = piece.zOrder + 1

      pieceLastSide = piece.setObstacle(pieceLastSide)

      piecesNode.position = ccpSub(piecesNode.position,
                                   CGPoint(x: 0, y: piece.contentSize.height))

      pieceIndex = (pieceIndex + 1) % 10

You might have noticed that pieceIndex hasn't be declared yet. Make sure to add the following near your other instance variables:

  var pieceIndex: Int = 0

Don't forget to call stepTower() every time you touch the screen! Add the method call to the bottom of your touch began function:

  override func touchBegan(touch: CCTouch!, withEvent event: CCTouchEvent!) {

Launch the game and play around a bit. You should have an infinitely looping tower of sushi with randomized obstacles!

Detect Collisions and Trigger Game Over

We already have a variable storing a Side in the Piece class but we need one in character before we get started. Add a side variable to the Character class. Also update the left() and right() methods accordingly.

Your Character class should now look like this:

  var side: Side = .Left

  func left() {
      side = .Left
      scaleX = 1

  func right() {
      side = .Right
      scaleX = -1

Now checking for collisions between the character and obstacles is as easy as comparing their side properties!

Add a gameOver instance variable to MainScene and complete the code connection to restartButton:

  var gameOver = false
  weak var restartButton: CCButton!

Create an isGameOver() -> Bool method in MainScene:

  func isGameOver() -> Bool {
      let newPiece = pieces[pieceIndex]

      if newPiece.side == character.side { triggerGameOver() }

      return gameOver

Also create triggerGameOver() in MainScene:

  func triggerGameOver() {
      gameOver = true
      restartButton.visible = true

The last step is to call isGameOver() at the appropriate times. Once a game over is triggered, the restart button will appear!

There are three types of collisions that trigger a game over in Timberman:

  1. switch into - player switched into base obstacle
  2. head-on - player continued into next obstacle
  3. switch into, head-on - player switched into next obstacle

We can catch the first one by checking right after moving the character (in touchBegan) and we can catch the others by checking right after the tower is stepped (in stepTower).

Add the line below to touchBegan right before stepTower is called:

  if isGameOver() { return }

Also add it at the end of stepTower.

Try out the game now. You'll realize that a restart button appears, but you can still continue to play and the restart button doesn't actually work.

Add the following line to the beginning of touchBegan:

  if gameOver { return }

We also need to define the restart() method for restartButton.

  func restart() {
      let scene = CCBReader.loadAsScene("MainScene")

Now that we short-circuit out of touchBegan after a game over, the player can no longer continue playing after a collision. restart() has also been defined so we can try again after losing.

The core gameplay is pretty close to completion. The only thing left is the timer and score!

Get the Timer Working

In Timberman there is a timer constantly counting down. Every successful move adds a little bit of time. You'll trigger a game over for running out of time if you don't play fast enough.

We are going to use property observers to update the scaleX of our lifeBar and an update() loop to decrement it.

First we need to complete the code connection for lifeBar. Add the following to MainScene near your instance variables:

  weak var lifeBar: CCSprite!

We also want to create an instance variable to track time left and set up a property observer on it to change scaleX on lifeBar whenever it changes. Add the following near your other instance variables:

  var timeLeft: Float = 5 {
      didSet {
          timeLeft = max(min(timeLeft, 10), 0)
          lifeBar.scaleX = timeLeft / Float(10)

The didSet property observer for timeLeft clamps the time between 0 and 10. After that, it sets the scaleX of lifeBar as a percentage of time left divided by 10 (the maximum amount of buffer the player can build).

Add the following to the end of stepTower():

  timeLeft = timeLeft + 0.25

And add an update loop to decrement timeLeft and trigger game over if the player runs out of time:

  override func update(delta: CCTime) {
      if gameOver { return }
      timeLeft -= Float(delta)
      if timeLeft == 0 {

It's safe to check if timeLeft is equal to zero since we clamped it in the didSet property observer.

The only thing left to do in core gameplay is implementing the score!

Update the Score

The score implementation is pretty similar the timer. We'll complete the scoreLabel code connection. Then we'll set up an instance variable with a didSet property observer to track the score and update the scoreLabel. Finally, we'll increment score at the end of stepTower.

Try and see if you can implement it on your own!

Add the following to complete the code connection for scoreLabel:

  weak var scoreLabel: CCLabelTTF!

Create a score instance variable with a didSet property observer to update scoreLabel:

  var score: Int = 0 {
      didSet {
          scoreLabel.string = "\(score)"

Increment score at the end of touchBegan:


Congrats! You have completed the core gameplay for Sushi Neko, a Timberman clone! Continue onto part two to polish up the gameplay :)


If you have feedback on this tutorial or find any mistakes, please open issues on the GitHub Repository.

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