Tag: Gaming

<== Lesson 3 || Lesson 5 ==>

This is a short lesson that adds a tad of challenge to trying to intercept the moving target.

The challenge is to increase the speed of each iteration of the moving target. The movingTargetDuration property has the length of time to “fall” from the top of the screen to the bottom. Progressively decreasing that value will increase the rate of movement for each interval.

However you eventually need to tweak game challenges so they are not impossible while remaining doable with practice. In this case a moving target duration below 2 appears to be close to the limit of impossible for the IPad in landscape mode.

Your testing may conclude differently that the speed could get higher. This is just a lesson and hopefully opens you to thoughts for varying the challenge. For example the decrease in the duration could be random number from a range say 0.0 – 0.2. Or you could have a random hyper change in the duration for one iteration only.

One other item that can vary the challenge is game levels. Our tutorial is limited to one level at this lesson. If more levels are added, then variations on the moving target speed, direction and size could be possible properties to add challenge.

Lesson Downloads

1. Game piece images for project
2. IPhone images for project. Icons and splash screen.
3. Completed Project. This is built in Kobold2d 1.0.1.

Step 1 – Build an Empty-Project Template

You can continue with the Lesson 3 project and make changes noted here. Otherwise the steps for creating this project from an Empty-Project template are the same as Lesson 1 except to substitute Lesson 4 for Lesson 1 in the project name and to include the red_ball.png and red_ball-hd.png files when you add the game pieces. Then you can use the code presented here.
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Step 2 – Set Properties in config.lua

There are no new configuration properties from Lesson 3. Complete config.lua file is included here for your copy convenience.

--[[
* Kobold2D™ --- http://www.kobold2d.org
*
* Copyright (c) 2010-2011 Steffen Itterheim. 
* Released under MIT License in Germany (LICENSE-Kobold2D.txt).
--]]


--[[
* Need help with the KKStartupConfig settings?
* ------ http://www.kobold2d.com/x/ygMO ------
--]]


local config =
{
    KKStartupConfig = 
    {
        -- load first scene from a class with this name, or from a Lua script with this name with .lua appended
        FirstSceneClassName = "GameLayer",

        -- set the director type, and the fallback in case the first isn't available
        DirectorType = DirectorType.DisplayLink,
        DirectorTypeFallback = DirectorType.NSTimer,

        MaxFrameRate = 60,
        DisplayFPS = YES,

        EnableUserInteraction = YES,
        EnableMultiTouch = NO,

        -- Render settings
        DefaultTexturePixelFormat = TexturePixelFormat.RGBA8888,
        GLViewColorFormat = GLViewColorFormat.RGB565,
        GLViewDepthFormat = GLViewDepthFormat.DepthNone,
        GLViewMultiSampling = NO,
        GLViewNumberOfSamples = 0,

        Enable2DProjection = NO,
        EnableRetinaDisplaySupport = YES,
        EnableGLViewNodeHitTesting = NO,
        EnableStatusBar = NO,

        -- Orientation & Autorotation
        DeviceOrientation = DeviceOrientation.LandscapeLeft,
        AutorotationType = Autorotation.None,
        ShouldAutorotateToLandscapeOrientations = NO,
        ShouldAutorotateToPortraitOrientations = NO,
        AllowAutorotateOnFirstAndSecondGenerationDevices = NO,

        -- Ad setup
        EnableAdBanner = NO,
        PlaceBannerOnBottom = YES,
        LoadOnlyPortraitBanners = NO,
        LoadOnlyLandscapeBanners = NO,
        AdProviders = "iAd, AdMob",	-- comma seperated list -> "iAd, AdMob" means: use iAd if available, otherwise AdMob
        AdMobRefreshRate = 15,
        AdMobFirstAdDelay = 5,
        AdMobPublisherID = "YOUR_ADMOB_PUBLISHER_ID", -- how to get an AdMob Publisher ID: http://developer.admob.com/wiki/PublisherSetup
        AdMobTestMode = YES,

        -- Mac OS specific settings
        AutoScale = NO,
        AcceptsMouseMovedEvents = NO,
        WindowFrame = RectMake(1024-640, 768-480, 640, 480),
        EnableFullScreen = NO,
    },
}

return config

Step 3 – GameLayer.h

No changes from Lesson 3. Complete GameLayer.h file is included here for your copy convenience.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "kobold2d.h"

@interface GameLayer : CCLayer
{
    CCSprite* player;
    CGPoint playerVelocity;
    CCSprite* movingTarget;
	float movingTargetMoveDuration;
}
@end

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Step 4 – Reduce Moving Target Animation Duration

Complete GameLayer.m file is included here for your copy convenience. We will just look at the code change up ahead for the endMovingTargetSequence method.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "GameLayer.h"

@interface GameLayer (PrivateMethods)
-(void) initMovingTarget;
-(void) movingTargetUpdate:(ccTime)delta;
-(void) startMovingTargetSequence;
-(void) endMovingTargetSequence;
@end

// Velocity deceleration
const float deceleration = 0.4f;
// Accelerometer sensitivity (higher = more sensitive)
const float sensitivity = 6.0f;
// Maximum velocity
const float maxVelocity = 100.0f;

@implementation GameLayer

-(id) init
{
	if ((self = [super init]))
	{
        // Enable accelerometer input events.
		[KKInput sharedInput].accelerometerActive = YES;
		[KKInput sharedInput].acceleration.filteringFactor = 0.2f;
        // Graphic for player
        player = [CCSprite spriteWithFile:@"green_ball.png"];
		[self addChild:player z:0 tag:1];
        // Position player        
        CGSize screenSize = [[CCDirector sharedDirector] winSize];
		float imageHeight = [player texture].contentSize.height;
		player.position = CGPointMake(screenSize.width / 2, imageHeight / 2);
		glClearColor(0.1f, 0.1f, 0.3f, 1.0f);
		// First line of title
		CCLabelTTF* label = [CCLabelTTF labelWithString:@"Kobold2d Intro Tutorial" 
                                               fontName:@"Arial"  
                                               fontSize:30];
		label.position = [CCDirector sharedDirector].screenCenter;
		label.color = ccCYAN;
        [self addChild:label];
        // Second line of title
 		CCLabelTTF* label2 = [CCLabelTTF labelWithString:@"Lesson 4"
                                                fontName:@"Arial"
                                                fontSize:24];
		label2.color = ccCYAN;
        label2.position = CGPointMake([CCDirector sharedDirector].screenCenter.x ,label.position.y - label.boundingBox.size.height);
        [self addChild:label2];
        // Seed random number generator
        srandom((UInt32)time(NULL));
        // Initialize our moving target.
        [self initMovingTarget];
        // Start animation -  the update method is called.
        [self scheduleUpdate];;
	}
	return self;
}
-(void) dealloc
{
#ifndef KK_ARC_ENABLED
	[super dealloc];
#endif // KK_ARC_ENABLED
}
#pragma mark Player Movement
-(void) acceleratePlayerWithX:(double)xAcceleration
{
    // Adjust velocity based on current accelerometer acceleration
    playerVelocity.x = (playerVelocity.x * deceleration) + (xAcceleration * sensitivity);
    // Limit the maximum velocity of the player sprite, in both directions (positive & negative values)
    if (playerVelocity.x > maxVelocity)
    {
        playerVelocity.x = maxVelocity;
    }
    else if (playerVelocity.x < -maxVelocity)
    {
        playerVelocity.x = -maxVelocity;
    }
}
#pragma mark update
-(void) update:(ccTime)delta
{
    // Gain access to the user input devices / states
    KKInput* input = [KKInput sharedInput];
    [self acceleratePlayerWithX:input.acceleration.smoothedX];
    // Accumulate up the playerVelocity to the player's position
    CGPoint pos = player.position;
    pos.x += playerVelocity.x;
    // The player constrainted to inside the screen
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Half the player image size player sprite position is the center of the image
    float imageWidthHalved = [player texture].contentSize.width * 0.5f;
    float leftBorderLimit = imageWidthHalved;
    float rightBorderLimit = screenSize.width - imageWidthHalved;
    // Hit left boundary
    if (pos.x < leftBorderLimit)
    {
        pos.x = leftBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Hit right boundary
    else if (pos.x > rightBorderLimit)
    {
        pos.x = rightBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Move the player
    player.position = pos; 
}  
#pragma mark MovingTarget

-(void) initMovingTarget
{
    NSLog(@"initMovingTarget");
    // This is the image
	movingTarget = [CCSprite spriteWithFile:@"red_ball.png"];
    // Add CCSprite for movingTarget
    [self addChild:movingTarget z:0 tag:2];
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
    movingTargetMoveDuration = 4.0f;
   	// Unschedule the selector just in case. If it isn't scheduled it won't do anything.
	[self unschedule:@selector(movingTargetUpdate:)];
	// Schedule the movingTarget update logic to run at the given interval.
	[self schedule:@selector(movingTargetUpdate:) interval:0.1f];
}

-(void) startMovingTargetSequence
{
    NSLog(@"startMovingTargetSequence");
    // Get the window size
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Get the image size
    CGSize imageSize = [movingTarget texture].contentSize;
    // Generate a random x starting position with offsets for center registration point.
    int randomX = CCRANDOM_0_1() * (screenSize.width / imageSize.width);
    movingTarget.position = CGPointMake(imageSize.width * randomX  + imageSize.width * 0.5f, screenSize.height + imageSize.height);
    // Schedule the movingTarget update logic to run at the given interval.
    [self schedule:@selector(movingTargetUpdate:) interval:0.1f];
}

-(void) movingTargetUpdate:(ccTime)delta
{
    // CCSprite->CCNode no sequence of actions running.
    if ([movingTarget numberOfRunningActions] == 0)
    {
        NSLog(@"movingTargetUpdate");
        // Determine below screen position.
        CGPoint belowScreenPosition = CGPointMake(movingTarget.position.x, - ( [movingTarget texture].contentSize.height));
        // CCAction to move a CCNode object to the position x,y based on position. 
        CCMoveTo* moveEnd = [CCMoveTo actionWithDuration:movingTargetMoveDuration position:belowScreenPosition];
        // Call back function for the action.
        CCCallFuncN* callEndMovingTargetSequence = [CCCallFuncN actionWithTarget:self selector:@selector(endMovingTargetSequence)];
        // Create a sequence, add the actions: the moveEnd CCMoveTo and the call back function for the end position.
        CCSequence* sequence = [CCSequence actions:moveEnd,callEndMovingTargetSequence, nil];
        // Run the sequence.
        [movingTarget runAction:sequence];
    }
}
-(void) endMovingTargetSequence
{
    NSLog(@"endMovingTargetSequence");
    // Terminate running the moveTargetUpdate interval.
    [self unschedule:@selector(movingTargetUpdate:)];
    // Decrease the moving target move duration to increase the speed.
    movingTargetMoveDuration -= 0.1f;
    // Moving target move duration is below 2 then hold at 2.
    if (movingTargetMoveDuration < 2.0f)
    {
        movingTargetMoveDuration = 2.0f;
    }
    NSLog(@"movingTargetMoveDuration: %f",movingTargetMoveDuration);
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
}

@end

The endMovingTargetSequence method is called when the moving target exits the bottom of the screen. That is set in the movingTargetUpdate method.

Line 173 of the endMovingTargetSequence method reduces the movingTargetMoveDuration class property by 0.1.

The movingTargetMoveDuration property starts at 4.0 in the initMovingTarget method.

Line 175 – 178 add a governor to prevent the duration from becoming less than 2.0.

As I mentioned earlier, you can be creative with ways to vary the moving target speed.

-(void) endMovingTargetSequence
{
    NSLog(@"endMovingTargetSequence");
    // Terminate running the moveTargetUpdate interval.
    [self unschedule:@selector(movingTargetUpdate:)];
    // Decrease the moving target move duration to increase the speed.
    movingTargetMoveDuration -= 0.1f;
    // Moving target move duration is below 2 then hold at 2.
    if (movingTargetMoveDuration < 2.0f)
    {
        movingTargetMoveDuration = 2.0f;
    }
    NSLog(@"movingTargetMoveDuration: %f",movingTargetMoveDuration);
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
}

<== Lesson 3 || Lesson 5 ==>

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<== Lesson 2 || Lesson 4 ==>

We have not discussed much about the nature of the game. Believe me it is relatively routine. The green player will try to intercept a falling red target.

The falling red target will start at random horizontal positions at the top of the screen and drop to the bottom of the screen. Only one red target falls at a time. The goal is to get the green player to intercept the falling red target.

In this lesson, we will add the falling red target but will not handle the collision. However, you can get some practice trying for later when you add a collision with sound and points.

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Lesson Downloads

1. Game piece images for project
2. IPhone images for project. Icons and splash screen.
3. Completed Project. This is built in Kobold2d 1.0.1.

Step 1 – Build an Empty-Project Template

You can continue with the Lesson 2 project and make changes noted here. Otherwise the steps for creating this project from an Empty-Project template are the same as Lesson 1 except to substitute Lesson 3 for Lesson 1 in the project name and to include the red_ball.png and red_ball-hd.png files when you add the game pieces. Then you can use the code presented here.

Step 2 – Set Properties in config.lua

There are no new property changes from lesson 2. All are included here for you to follow along.

--[[
* Kobold2D™ --- http://www.kobold2d.org
*
* Copyright (c) 2010-2011 Steffen Itterheim. 
* Released under MIT License in Germany (LICENSE-Kobold2D.txt).
--]]


--[[
* Need help with the KKStartupConfig settings?
* ------ http://www.kobold2d.com/x/ygMO ------
--]]


local config =
{
    KKStartupConfig = 
    {
        -- load first scene from a class with this name, or from a Lua script with this name with .lua appended
        FirstSceneClassName = "GameLayer",

        -- set the director type, and the fallback in case the first isn't available
        DirectorType = DirectorType.DisplayLink,
        DirectorTypeFallback = DirectorType.NSTimer,

        MaxFrameRate = 60,
        DisplayFPS = YES,

        EnableUserInteraction = YES,
        EnableMultiTouch = NO,

        -- Render settings
        DefaultTexturePixelFormat = TexturePixelFormat.RGBA8888,
        GLViewColorFormat = GLViewColorFormat.RGB565,
        GLViewDepthFormat = GLViewDepthFormat.DepthNone,
        GLViewMultiSampling = NO,
        GLViewNumberOfSamples = 0,

        Enable2DProjection = NO,
        EnableRetinaDisplaySupport = YES,
        EnableGLViewNodeHitTesting = NO,
        EnableStatusBar = NO,

        -- Orientation & Autorotation
        DeviceOrientation = DeviceOrientation.LandscapeRight,
        AutorotationType = Autorotation.None,
        ShouldAutorotateToLandscapeOrientations = NO,
        ShouldAutorotateToPortraitOrientations = NO,
        AllowAutorotateOnFirstAndSecondGenerationDevices = NO,

        -- Ad setup
        EnableAdBanner = NO,
        PlaceBannerOnBottom = YES,
        LoadOnlyPortraitBanners = NO,
        LoadOnlyLandscapeBanners = NO,
        AdProviders = "iAd, AdMob",	-- comma seperated list -> "iAd, AdMob" means: use iAd if available, otherwise AdMob
        AdMobRefreshRate = 15,
        AdMobFirstAdDelay = 5,
        AdMobPublisherID = "YOUR_ADMOB_PUBLISHER_ID", -- how to get an AdMob Publisher ID: http://developer.admob.com/wiki/PublisherSetup
        AdMobTestMode = YES,

        -- Mac OS specific settings
        AutoScale = NO,
        AcceptsMouseMovedEvents = NO,
        WindowFrame = RectMake(1024-640, 768-480, 640, 480),
        EnableFullScreen = NO,
    },
}

return config

Step 3 – Add Moving Target Properties to GameLayer.h File

A CCSprite Cocos2d object is responsible for our target shown on line 14. CCSprite represents a 2d image and inherits from CCNode.

The movingTargetDuration float is the speed of the target fall from the top of the screen.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "kobold2d.h"

@interface GameLayer : CCLayer
{
    CCSprite* player;
    CGPoint playerVelocity;
    CCSprite* movingTarget;
	float movingTargetMoveDuration;
}
@end

Step 4 – Integrate Moving Target Into to GameLayer.m File

I am going to discuss specific sections of the GameLayer.m file in this post. Meantime for the impatient, like me, here here is the full GameLayer.m source code for your copy and paste convenience.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "GameLayer.h"

@interface GameLayer (PrivateMethods)
-(void) initMovingTarget;
-(void) movingTargetUpdate:(ccTime)delta;
-(void) startMovingTargetSequence;
-(void) endMovingTargetSequence;
@end

// Velocity deceleration
const float deceleration = 0.4f;
// Accelerometer sensitivity (higher = more sensitive)
const float sensitivity = 6.0f;
// Maximum velocity
const float maxVelocity = 100.0f;

@implementation GameLayer

-(id) init
{
	if ((self = [super init]))
	{
        // Enable accelerometer input events.
		[KKInput sharedInput].accelerometerActive = YES;
		[KKInput sharedInput].acceleration.filteringFactor = 0.2f;
        // Graphic for player
        player = [CCSprite spriteWithFile:@"green_ball.png"];
		[self addChild:player z:0 tag:1];
        // Position player        
        CGSize screenSize = [[CCDirector sharedDirector] winSize];
		float imageHeight = [player texture].contentSize.height;
		player.position = CGPointMake(screenSize.width / 2, imageHeight / 2);
		glClearColor(0.1f, 0.1f, 0.3f, 1.0f);
		// First line of title
		CCLabelTTF* label = [CCLabelTTF labelWithString:@"Kobold2d Intro Tutorial" 
                                               fontName:@"Arial"  
                                               fontSize:30];
		label.position = [CCDirector sharedDirector].screenCenter;
		label.color = ccCYAN;
        [self addChild:label];
        // Second line of title
 		CCLabelTTF* label2 = [CCLabelTTF labelWithString:@"Lesson 3"
                                                fontName:@"Arial"
                                                fontSize:24];
		label2.color = ccCYAN;
        label2.position = CGPointMake([CCDirector sharedDirector].screenCenter.x ,label.position.y - label.boundingBox.size.height);
        [self addChild:label2];
        // Seed random number generator
        srandom((UInt32)time(NULL));
        // Initialize our moving target.
        [self initMovingTarget];
        // Start animation -  the update method is called.
        [self scheduleUpdate];;
	}
	return self;
}
-(void) dealloc
{
#ifndef KK_ARC_ENABLED
	[super dealloc];
#endif // KK_ARC_ENABLED
}
#pragma mark Player Movement
-(void) acceleratePlayerWithX:(double)xAcceleration
{
    // Adjust velocity based on current accelerometer acceleration
    playerVelocity.x = (playerVelocity.x * deceleration) + (xAcceleration * sensitivity);
    // Limit the maximum velocity of the player sprite, in both directions (positive & negative values)
    if (playerVelocity.x > maxVelocity)
    {
        playerVelocity.x = maxVelocity;
    }
    else if (playerVelocity.x < -maxVelocity)
    {
        playerVelocity.x = -maxVelocity;
    }
}
#pragma mark update
-(void) update:(ccTime)delta
{
    // Gain access to the user input devices / states
    KKInput* input = [KKInput sharedInput];
    [self acceleratePlayerWithX:input.acceleration.smoothedX];
    // Accumulate up the playerVelocity to the player's position
    CGPoint pos = player.position;
    pos.x += playerVelocity.x;
    // The player constrainted to inside the screen
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Half the player image size player sprite position is the center of the image
    float imageWidthHalved = [player texture].contentSize.width * 0.5f;
    float leftBorderLimit = imageWidthHalved;
    float rightBorderLimit = screenSize.width - imageWidthHalved;
    // Hit left boundary
    if (pos.x < leftBorderLimit)
    {
        pos.x = leftBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Hit right boundary
    else if (pos.x > rightBorderLimit)
    {
        pos.x = rightBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Move the player
    player.position = pos; 
}  
#pragma mark MovingTarget

-(void) initMovingTarget
{
    NSLog(@"initMovingTarget");
    // This is the image
	movingTarget = [CCSprite spriteWithFile:@"red_ball.png"];
    // Add CCSprite for movingTarget
    [self addChild:movingTarget z:0 tag:2];
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
    movingTargetMoveDuration = 4.0f;
   	// Unschedule the selector just in case. If it isn't scheduled it won't do anything.
	[self unschedule:@selector(movingTargetUpdate:)];
	// Schedule the movingTarget update logic to run at the given interval.
	[self schedule:@selector(movingTargetUpdate:) interval:0.1f];
}

-(void) startMovingTargetSequence
{
    NSLog(@"startMovingTargetSequence");
    // Get the window size
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Get the image size
    CGSize imageSize = [movingTarget texture].contentSize;
    // Generate a random x starting position with offsets for center registration point.
    int randomX = CCRANDOM_0_1() * (screenSize.width / imageSize.width);
    movingTarget.position = CGPointMake(imageSize.width * randomX  + imageSize.width * 0.5f, screenSize.height + imageSize.height);
    // Schedule the movingTarget update logic to run at the given interval.
    [self schedule:@selector(movingTargetUpdate:) interval:0.1f];
}

-(void) movingTargetUpdate:(ccTime)delta
{
    // CCSprite->CCNode no sequence of actions running.
    if ([movingTarget numberOfRunningActions] == 0)
    {
        NSLog(@"movingTargetUpdate");
        // Determine below screen position.
        CGPoint belowScreenPosition = CGPointMake(movingTarget.position.x, - ( [movingTarget texture].contentSize.height));
        // CCAction to move a CCNode object to the position x,y based on position. 
        CCMoveTo* moveEnd = [CCMoveTo actionWithDuration:movingTargetMoveDuration position:belowScreenPosition];
        // Call back function for the action.
        CCCallFuncN* callEndMovingTargetSequence = [CCCallFuncN actionWithTarget:self selector:@selector(endMovingTargetSequence)];
        // Create a sequence, add the actions: the moveEnd CCMoveTo and the call back function for the end position.
        CCSequence* sequence = [CCSequence actions:moveEnd,callEndMovingTargetSequence, nil];
        // Run the sequence.
        [movingTarget runAction:sequence];
    }
}
-(void) endMovingTargetSequence
{
    NSLog(@"endMovingTargetSequence");
    // Terminate running the moveTargetUpdate interval.
    [self unschedule:@selector(movingTargetUpdate:)];
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
}

@end

These methods are private and so we are declaring them in the implementation file. They are for controlling your moving target. We will talk more about them one at time.

#import "GameLayer.h"

@interface GameLayer (PrivateMethods)
-(void) initMovingTarget;
-(void) movingTargetUpdate:(ccTime)delta;
-(void) startMovingTargetSequence;
-(void) endMovingTargetSequence;
@end

Step 5 – Integrate Moving Target into GameLayer.h File init method

To keep the eye clear which lesson you are viewing, change the subtitle on line 49.

You have the initMovingTarget method to handle creating our moving target. Line 58 is added to call the initMovingTarget.

You need to place the moving target at various horizontal positions on the top of the screen. We are using CCRANDOM_0_1() for the randomization. CCRANDOM_0_1() needs a one time seeding shown on line 56.

@implementation GameLayer

-(id) init
{
	if ((self = [super init]))
	{
        // Enable accelerometer input events.
		[KKInput sharedInput].accelerometerActive = YES;
		[KKInput sharedInput].acceleration.filteringFactor = 0.2f;
        // Graphic for player
        player = [CCSprite spriteWithFile:@"green_ball.png"];
		[self addChild:player z:0 tag:1];
        // Position player        
        CGSize screenSize = [[CCDirector sharedDirector] winSize];
		float imageHeight = [player texture].contentSize.height;
		player.position = CGPointMake(screenSize.width / 2, imageHeight / 2);
		glClearColor(0.1f, 0.1f, 0.3f, 1.0f);
		// First line of title
		CCLabelTTF* label = [CCLabelTTF labelWithString:@"Kobold2d Intro Tutorial" 
                                               fontName:@"Arial"  
                                               fontSize:30];
		label.position = [CCDirector sharedDirector].screenCenter;
		label.color = ccCYAN;
        [self addChild:label];
        // Second line of title
 		CCLabelTTF* label2 = [CCLabelTTF labelWithString:@"Lesson 3"
                                                fontName:@"Arial"
                                                fontSize:24];
		label2.color = ccCYAN;
        label2.position = CGPointMake([CCDirector sharedDirector].screenCenter.x ,label.position.y - label.boundingBox.size.height);
        [self addChild:label2];
        // Seed random number generator
        srandom((UInt32)time(NULL));
        // Initialize our moving target.
        [self initMovingTarget];
        // Start animation -  the update method is called.
        [self scheduleUpdate];;
	}
	return self;
}

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Step 6 – Add the initMoving Target Method

You can see on line 123 the red_ball.png is the graphic image for the moving target.

On line 125 the moving target is added. The z order is zero for this lesson. The tag value I mentioned in Lesson 1 as another way to get references to sprite objects. We are not using tags but since the game player has a tag value of 1, the moving target needed a different number. How about 2?

One line 127 the startMovingTargetSequence method for the initial start position of the moving target is called.

Line 128 sets the moving target moving duration value. For now the value never changes. But to add some variety to the game in a future lesson, we will decrease the value to speed up the moving target drop speed. The point is there needs to be a place to set the initial value.

One line 130 a standard safety precaution cancels the movingTargetUpdate method from being called. This method gets the target moving and we will look at it in a bit. At this point it is not possible to call initiMovingTarget more than once. However later it might happen this initMovingTarget method is called more than once and we have stopped any sequence from running.

Finally line 132 gets the moving target into motion. The movingTargetUpdate method defines that motion.

-(void) initMovingTarget
{
    NSLog(@"initMovingTarget");
    // This is the image
	movingTarget = [CCSprite spriteWithFile:@"red_ball.png"];
    // Add CCSprite for movingTarget
    [self addChild:movingTarget z:0 tag:2];
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
    movingTargetMoveDuration = 4.0f;
   	// Unschedule the selector just in case. If it isn't scheduled it won't do anything.
	[self unschedule:@selector(movingTargetUpdate:)];
	// Schedule the movingTarget update logic to run at the given interval.
	[self schedule:@selector(movingTargetUpdate:) interval:0.1f];
}

Step 7 – Add the startMovingTargetSequence Target Method
This method through line 144 provides the starting point for the moving target object.

Then on line 146, the movingTargetUpdate method is scheduled for call. That is where the animation sequence for the moving target is created.

-(void) startMovingTargetSequence
{
    NSLog(@"startMovingTargetSequence");
    // Get the window size
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Get the image size
    CGSize imageSize = [movingTarget texture].contentSize;
    // Generate a random x starting position with offsets for center registration point.
    int randomX = CCRANDOM_0_1() * (screenSize.width / imageSize.width);
    movingTarget.position = CGPointMake(imageSize.width * randomX  + imageSize.width * 0.5f, screenSize.height + imageSize.height);
    // Schedule the movingTarget update logic to run at the given interval.
    [self schedule:@selector(movingTargetUpdate:) interval:0.1f];
}

Step 8 – Add the movingTargetUpdate Target Method

The movingTargetIUpdate method creates two CCAction objects.

The first is CCMoveTo on line 158. This is the destination of the moving target. The current y position and the belowScreenPosition y are traversed over the movingTargetMoveDuration value.

Line 160 creates the second CCCallFuncN to identify calling the endMovingTargetSequence method to handle the end of the animation.

These two CCAction objects are then bundled on line 162 into a CCSequence CCAction. CCSequence is essentially an array.

Line 164 runs the actions in the CCSequence.

So the CCMoveTo CCAction is processed over the movingTargetMoveDuration and on its conclusion the CCCallFuncN CCAction invokes the endMovingTargetSequence method for cleanup.

-(void) movingTargetUpdate:(ccTime)delta
{
    // CCSprite->CCNode no sequence of actions running.
    if ([movingTarget numberOfRunningActions] == 0)
    {
        NSLog(@"movingTargetUpdate");
        // Determine below screen position.
        CGPoint belowScreenPosition = CGPointMake(movingTarget.position.x, - ( [movingTarget texture].contentSize.height));
        // CCAction to move a CCNode object to the position x,y based on position. 
        CCMoveTo* moveEnd = [CCMoveTo actionWithDuration:movingTargetMoveDuration position:belowScreenPosition];
        // Call back function for the action.
        CCCallFuncN* callEndMovingTargetSequence = [CCCallFuncN actionWithTarget:self selector:@selector(endMovingTargetSequence)];
        // Create a sequence, add the actions: the moveEnd CCMoveTo and the call back function for the end position.
        CCSequence* sequence = [CCSequence actions:moveEnd,callEndMovingTargetSequence, nil];
        // Run the sequence.
        [movingTarget runAction:sequence];
    }
}

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Step 9 – Add the endMovingTargetSequence Target Method

This is the end of the moving target animation. The movingTargetUpdate method is removed as a scheduled method on line 171,

Line 172 then sets up for the next moving target for a repeat performance.

-(void) endMovingTargetSequence
{
    NSLog(@"endMovingTargetSequence");
    // Terminate running the moveTargetUpdate interval.
    [self unschedule:@selector(movingTargetUpdate:)];
    // Set the starting position and start movingTarget play sequence
    [self startMovingTargetSequence];
}

<== Lesson 2 || Lesson 4 ==>

<== Lesson 1 || Lesson 3 ==>

The first lesson put into place all the accelerometer code for our game. However we want the game to run only in landscape orientation.

KKStartupConfig – Setting the device orientation in Kobold2D is done in the config.lua configuration file. We saw in the last lesson the use of FirstSceneClassName for the KKStartupConfig object. FirstSceneClassName is a property for KKStartupConfig. The documentation for KKStartupConfig lists all the properties and valid values.

DeviceOrientation – One of the KKStartupConfig properties is DeviceOrientation. This is an int data type and has four values: DeviceOrientation.Portrait, DeviceOrientation.PortraitUpsideDown, DeviceOrientation.LandscapeLeft, and DeviceOrientation.LandscapeRight.

You can think of them based on where the home button is located. For DeviceOrientation.Portrait the home button is on the bottom where you might expect. For DeviceOrientation.PortraitUpsideDown the home button on top. The home button is to the right for DeviceOrientation.LandscapeLeft to the left for DeviceOrientation.LandscapeRight.

AutoRotationType – Another KKStartupConfig property dealing with rotation is AutoRotationType. This is an int and has these values: Autorotation.None, Autorotation.CCDirector, and Autorotation.UIViewController.

The None setting will never rotate your app’s device orientation. This is the setting we want.

The CCDirector setting makes the CCDirector responsible for rotating the OpenGL view but it will not auto rotate UIKit Views.

The UIViewController setting allows both UIKit views and the OpenGL view to be auto rotated and provides a rotation animation. But it comes with a performance penalty on 1st and 2nd generation iOS Devices. For that reason you can explicitly disable auto rotation on those devices via the AllowAutorotateOnFirstAndSecondGenerationDevices KKStartiupConfig property. We set AllowAutorotateOnFirstAndSecondGenerationDevices to false as we are not supporting older devices.

ShouldAutorotateTo… – Two other rotation KKStartupConfig properties are ShouldAutorotateToLandscapeOrientations and ShouldAutorotateToPortraitOrientations both boolean values. They explicitly restrict auto rotation and are useful when your game does not have alternative views.

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Lesson Downloads

1. Game piece images for project
2. IPhone images for project. Icons and splash screen.
3. Completed Project. This is built in Kobold2d 1.0.1.

Step 1 – Build an Empty-Project Template

You can continue with the Lesson 1 project and make changes noted here. Otherwise the steps for creating this project from an Empty-Project template are the same as Lesson 1 except to substitute Lesson 2 for Lesson 1 in the project name.

Step 2 – Set the Orientation Properties in config.lua

This is the config.lua file located in the Projectfiles->Resources group.

Lines 43- 47 show the KKStartupConfig properties set for this lesson. Essentially our settings are saying to set the DeviceOrientation to LandscapeRight so the home button appears on the left and prevent any other orientation change.

Also take note to line 18 updated as a developer choice for the first scene game class.

--[[
* Kobold2D™ --- http://www.kobold2d.org
*
* Copyright (c) 2010-2011 Steffen Itterheim. 
* Released under MIT License in Germany (LICENSE-Kobold2D.txt).
--]]


--[[
* Need help with the KKStartupConfig settings?
* ------ http://www.kobold2d.com/x/ygMO ------
--]]


local config =
{
    KKStartupConfig = 
    {
        -- load first scene from a class with this name, or from a Lua script with this name with .lua appended
        FirstSceneClassName = "GameLayer",

        -- set the director type, and the fallback in case the first isn't available
        DirectorType = DirectorType.DisplayLink,
        DirectorTypeFallback = DirectorType.NSTimer,

        MaxFrameRate = 60,
        DisplayFPS = YES,

        EnableUserInteraction = YES,
        EnableMultiTouch = NO,

        -- Render settings
        DefaultTexturePixelFormat = TexturePixelFormat.RGBA8888,
        GLViewColorFormat = GLViewColorFormat.RGB565,
        GLViewDepthFormat = GLViewDepthFormat.DepthNone,
        GLViewMultiSampling = NO,
        GLViewNumberOfSamples = 0,

        Enable2DProjection = NO,
        EnableRetinaDisplaySupport = YES,
        EnableGLViewNodeHitTesting = NO,
        EnableStatusBar = NO,

        -- Orientation & Autorotation
        DeviceOrientation = DeviceOrientation.LandscapeRight,
        AutorotationType = Autorotation.None,
        ShouldAutorotateToLandscapeOrientations = NO,
        ShouldAutorotateToPortraitOrientations = NO,
        AllowAutorotateOnFirstAndSecondGenerationDevices = NO,

        -- Ad setup
        EnableAdBanner = NO,
        PlaceBannerOnBottom = YES,
        LoadOnlyPortraitBanners = NO,
        LoadOnlyLandscapeBanners = NO,
        AdProviders = "iAd, AdMob",	-- comma seperated list -> "iAd, AdMob" means: use iAd if available, otherwise AdMob
        AdMobRefreshRate = 15,
        AdMobFirstAdDelay = 5,
        AdMobPublisherID = "YOUR_ADMOB_PUBLISHER_ID", -- how to get an AdMob Publisher ID: http://developer.admob.com/wiki/PublisherSetup
        AdMobTestMode = YES,

        -- Mac OS specific settings
        AutoScale = NO,
        AcceptsMouseMovedEvents = NO,
        WindowFrame = RectMake(1024-640, 768-480, 640, 480),
        EnableFullScreen = NO,
    },
}

return config

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Step 3 – Update the Lesson Subtitle in the GameLayer.m file

Line 45 of the Lesson 2 GameLayer.m file updates the subtitle and included here for completeness. But you can see no other programming changes to control the orientation.

Notice on line 33 and 88 that we did not change but still allows the game to know the dimensions of the screen despite the landscape orientation.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "GameLayer.h"

@interface GameLayer (PrivateMethods)
@end

// Velocity deceleration
const float deceleration = 0.4f;
// Accelerometer sensitivity (higher = more sensitive)
const float sensitivity = 6.0f;
// Maximum velocity
const float maxVelocity = 100.0f;

@implementation GameLayer

-(id) init
{
	if ((self = [super init]))
	{
        // Enable accelerometer input events.
		[KKInput sharedInput].accelerometerActive = YES;
		[KKInput sharedInput].acceleration.filteringFactor = 0.2f;
        // Graphic for player
        player = [CCSprite spriteWithFile:@"green_ball.png"];
		[self addChild:player z:0 tag:1];
        // Position player        
        CGSize screenSize = [[CCDirector sharedDirector] winSize];
		float imageHeight = [player texture].contentSize.height;
		player.position = CGPointMake(screenSize.width / 2, imageHeight / 2);
		glClearColor(0.1f, 0.1f, 0.3f, 1.0f);
		// First line of title
		CCLabelTTF* label = [CCLabelTTF labelWithString:@"Kobold2d Intro Tutorial" 
                                               fontName:@"Arial"  
                                               fontSize:30];
		label.position = [CCDirector sharedDirector].screenCenter;
		label.color = ccCYAN;
        [self addChild:label];
        // Second line of title
 		CCLabelTTF* label2 = [CCLabelTTF labelWithString:@"Lesson 2"
                                                fontName:@"Arial"
                                                fontSize:24];
		label2.color = ccCYAN;
        label2.position = CGPointMake([CCDirector sharedDirector].screenCenter.x ,label.position.y - label.boundingBox.size.height);
        [self addChild:label2];
        // Start animation -  the update method is called.
        [self scheduleUpdate];;
	}
	return self;
}
-(void) dealloc
{
#ifndef KK_ARC_ENABLED
	[super dealloc];
#endif // KK_ARC_ENABLED
}

#pragma mark Player Movement
-(void) acceleratePlayerWithX:(double)xAcceleration
{
    // Adjust velocity based on current accelerometer acceleration
    playerVelocity.x = (playerVelocity.x * deceleration) + (xAcceleration * sensitivity);
    // Limit the maximum velocity of the player sprite, in both directions (positive & negative values)
    if (playerVelocity.x > maxVelocity)
    {
        playerVelocity.x = maxVelocity;
    }
    else if (playerVelocity.x < -maxVelocity)
    {
        playerVelocity.x = -maxVelocity;
    }
}
#pragma mark update
-(void) update:(ccTime)delta
{
    // Gain access to the user input devices / states
    KKInput* input = [KKInput sharedInput];
    [self acceleratePlayerWithX:input.acceleration.smoothedX];
    // Accumulate up the playerVelocity to the player's position
    CGPoint pos = player.position;
    pos.x += playerVelocity.x;
    // The player constrainted to inside the screen
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Half the player image size player sprite position is the center of the image
    float imageWidthHalved = [player texture].contentSize.width * 0.5f;
    float leftBorderLimit = imageWidthHalved;
    float rightBorderLimit = screenSize.width - imageWidthHalved;
    // Hit left boundary
    if (pos.x < leftBorderLimit)
    {
        pos.x = leftBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Hit right boundary
    else if (pos.x > rightBorderLimit)
    {
        pos.x = rightBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Move the player
    player.position = pos; 
}  
@end

Step 4 – GameLayer.h file

There are no changes from Lesson 1 for the GameLayer.h file. It is included here for completeness.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "kobold2d.h"

@interface GameLayer : CCLayer
{
    CCSprite* player;
    CGPoint playerVelocity;
}
@end

<== Lesson 1 || Lesson 3 ==>

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Lesson 2 ==>

This first lesson goes through the steps to set up a Kobold2D project in XCode and use the accelerometer in the IPhone or IPad.

I am going to focus on the IPad, but the example should work fine in an IPhone as well. The example is very simple and is not yet a game. As the lessons continue a basic game will emerge.

Kobold2D is based on Cocos2D for IPhone project. Kobold2D helps make developing games in Cocos2D easier.

The example works in portrait orientation. Later lessons you change the orientation. Their is a green circle graphic that sits at the bottom of the screen and you can move it left and right by tilting the device. The accelerometer data is read and using some basic velocity adjustments the image moves until it reaches an edge. Here is a screen shot of the completed project.

The frames per second indicator is an option you will see later in the config.lua file.

You need to download and install Kobold2D and XCode.

Lesson Downloads

1. Images for project
2. Completed Project. This is built in Kobold2d 1.0.1.

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Step 1: Start a New Kobold2D Project

Kobold2D handles the creating of XCode projects through its own utility. Currently the recommendation is to close XCode before creating a new Kobold2D project.

Find the folder you installed Kobold2D and then launch the Kobold2D Project Starter application.

Step 2: Select the Empty-Project Template

You are going to start with a bare bones project. The project will actually run but only displays a default splash screen and title screen.

Select an XCode workspace. The default KBold2d.xcworkspace is fine. All Kobold2d projects must be in an XCode workspace. This will appear to be an overkill once you get into XCode such as the Run shows all workspace projects and each with their own targets. You will find launching the wrong project a common problem.

You can create a new workspace here by typing the name. For now we are staying with the default KBold2d.xcworkspace workspace.

Type a project name and click the Create Project from Template button.

Step 3: Add IOS Icons

This step is optional as there will be default Kobold2d icons ready in your project. However if you have your own set you need to copy over them outside of XCode since they are already referenced in the XCode project. I provided a download of the various IOS icons in case you want to practice this step. Copy them as per this image.

Step 4: Add Game Player Images

The game pieces are provided in the download. There is a low and high resolution version named according to the XCode IOS conventions. They are going to be in the Project Files->Resources group. You must copy them from the Finder into the XCode project navigator shown as follows:

Here is the “Choose options for adding these files” dialog. Check “Copy items into destination group’s folder (if needed)”. “Create folder references for any added folders” option is selected although it does not apply as we are not copying folders.

Finally Kobold2D is set up to build your game for a Mac delivery if you choose. We are building for IOS and so you can choose -IOS choice which is proceeded by the name you gave to the project. In our case the “Intro_Tutorial_Lesson_01-IOS”

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Step 5: Naming the Game Layer Class Files

The default name for the Game Layer class is HelloWorldLayer. We can leave that and proceed without any issues. But most developers want more control over the name of classes.

Plus you get to see the first glimpse to the internal workings of Kobold2D with the Lua file used for game configuration choices. One configuration is the main game layer class name.

In the project explorer window rename the HelloWorldLayer.h and HelloWorldLayer.m files to GameLayer.h and GameLayer.m files respectively.

Now open the config.lua file. You find this in the ProjectFiles->Resources folder. It is a text file. Change line 18 as you see below. You can look over some of the other potential configuration choices we can use as our work progress such as lines 42- 47 for controlling device orientation.

Line 25 for example contains the DisplayFPS to toggle the viewing of the frames per second. You might use this for testing when your game has performance issues. We will leave it on and you should see the 60 frames per second that is defined on line 24 most of the time for this lesson project.

As well you can add our own configuration variables to this file. A future lesson will provide an example.

--[[
* Kobold2D™ --- http://www.kobold2d.org
*
* Copyright (c) 2010-2011 Steffen Itterheim. 
* Released under MIT License in Germany (LICENSE-Kobold2D.txt).
--]]


--[[
* Need help with the KKStartupConfig settings?
* ------ http://www.kobold2d.com/x/ygMO ------
--]]


local config =
{
    KKStartupConfig = 
    {
        -- load first scene from a class with this name, or from a Lua script with this name with .lua appended
        FirstSceneClassName = "GameLayer",

        -- set the director type, and the fallback in case the first isn't available
        DirectorType = DirectorType.DisplayLink,
        DirectorTypeFallback = DirectorType.NSTimer,

        MaxFrameRate = 60,
        DisplayFPS = YES,

        EnableUserInteraction = YES,
        EnableMultiTouch = NO,

        -- Render settings
        DefaultTexturePixelFormat = TexturePixelFormat.RGBA8888,
        GLViewColorFormat = GLViewColorFormat.RGB565,
        GLViewDepthFormat = GLViewDepthFormat.DepthNone,
        GLViewMultiSampling = NO,
        GLViewNumberOfSamples = 0,

        Enable2DProjection = NO,
        EnableRetinaDisplaySupport = YES,
        EnableGLViewNodeHitTesting = NO,
        EnableStatusBar = NO,

        -- Orientation & Autorotation
        DeviceOrientation = DeviceOrientation.Portrait,
        AutorotationType = Autorotation.CCDirector,
        ShouldAutorotateToLandscapeOrientations = NO,
        ShouldAutorotateToPortraitOrientations = YES,
        AllowAutorotateOnFirstAndSecondGenerationDevices = YES,

        -- Ad setup
        EnableAdBanner = NO,
        PlaceBannerOnBottom = YES,
        LoadOnlyPortraitBanners = NO,
        LoadOnlyLandscapeBanners = NO,
        AdProviders = "iAd, AdMob",	-- comma seperated list -> "iAd, AdMob" means: use iAd if available, otherwise AdMob
        AdMobRefreshRate = 15,
        AdMobFirstAdDelay = 5,
        AdMobPublisherID = "YOUR_ADMOB_PUBLISHER_ID", -- how to get an AdMob Publisher ID: http://developer.admob.com/wiki/PublisherSetup
        AdMobTestMode = YES,

        -- Mac OS specific settings
        AutoScale = NO,
        AcceptsMouseMovedEvents = NO,
        WindowFrame = RectMake(1024-640, 768-480, 640, 480),
        EnableFullScreen = NO,
    },
}

return config

Next each GameLayer.h and GameLayer.m file needs to be edited to replace HelloWorldLayer with GameLayer. I will point out those changes as their code is explored for this lesson.

Step 6: The GameLayer.h File

Our header file is rather simple.

First be sure you change HelloWorldLayer to GameLayer on line 10.

On line 12 we define a CCSprite. This defines a 2d image game sprite for our game.

Line 13 defines the velocity for the player. This is a CGPoint object defined as “a structure that contains a point in a two-dimensional coordinate system”. In other words an x and y value.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "kobold2d.h"

@interface GameLayer : CCLayer
{
    CCSprite* player;
    CGPoint playerVelocity;
}
@end

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Step 7: The GameLayer.m File

First you need to rename HelloWorldLayer to GameLayer on lines 8, 10 , 20 highlighted so you do not miss them.

Constants defined here include the deceleration of the x velocity of our player at 40%. You can play with the responsiveness of of the accelerometer. The value of 6 seems to work well. Last is the fastest movement for the x velocity of our player.

/*
 * Kobold2D™ --- http://www.kobold2d.org
 *
 * Copyright (c) 2010-2011 Steffen Itterheim. 
 * Released under MIT License in Germany (LICENSE-Kobold2D.txt).
 */

#import "GameLayer.h"

@interface GameLayer (PrivateMethods)
@end

// Velocity deceleration
const float deceleration = 0.4f;
// Accelerometer sensitivity (higher = more sensitive)
const float sensitivity = 6.0f;
// Maximum velocity
const float maxVelocity = 100.0f;

@implementation GameLayer

The init method allows us to set up basic elements in the game.

Line 27 gets the accelerometer involved. Line 28 sets the filtering in a range of 0 to 1 to respond to movements of the device. Here you are looking for impact of spikes.

Line 30 and 31 adds our player sprite. The z argument is for layering. The tag argument is for developers to use to identify sprites in other Kobol2D methods without having to reference or create a CCSprite object. We do not have a use of the tag property at this point.

Lines 33-35 are for horizontally centering our player. The CCDirector class gives us access to the viewing size with the winSize property. The CCDirector is a Cocos2D class creates and handle the main Window and manages how and when to execute the Scenes.

Line 36 gives the bluish background color. The glClearColor function is clearing the graphics layer.

Lines 38 – 50 demonstrate how to add labels to the game. There are two lines of labels for this example.

The positioning takes advantage of the CCDirector screenCenter property for the first label. The second label uses screenCenter for the x property and offsets against the first label’s y position.

The ccCyan is the color for the text.

The scheduleUpdate method on line 52 calls the update method as often as possible up to the MaxFrameRate set in the config.lua file.

-(id) init
{
	if ((self = [super init]))
	{
        // Enable accelerometer input events.
		[KKInput sharedInput].accelerometerActive = YES;
		[KKInput sharedInput].acceleration.filteringFactor = 0.2f;
        // Graphic for player
        player = [CCSprite spriteWithFile:@"green_ball.png"];
		[self addChild:player z:0 tag:1];
        // Position player        
        CGSize screenSize = [[CCDirector sharedDirector] winSize];
		float imageHeight = [player texture].contentSize.height;
		player.position = CGPointMake(screenSize.width / 2, imageHeight / 2);
		glClearColor(0.1f, 0.1f, 0.3f, 1.0f);
		// First line of title
		CCLabelTTF* label = [CCLabelTTF labelWithString:@"Kobold2d Intro Tutorial" 
                                               fontName:@"Arial"  
                                               fontSize:30];
		label.position = [CCDirector sharedDirector].screenCenter;
		label.color = ccCYAN;
        [self addChild:label];
        // Second line of title
 		CCLabelTTF* label2 = [CCLabelTTF labelWithString:@"Lesson 1"
                                                fontName:@"Arial"
                                                fontSize:24];
		label2.color = ccCYAN;
        label2.position = CGPointMake([CCDirector sharedDirector].screenCenter.x ,label.position.y - label.boundingBox.size.height);
        [self addChild:label2];
        // Start animation -  the update method is called.
        [self scheduleUpdate];;
	}
	return self;
}

These next lines handle the case of using automatic reference counting added with the XCode 4.2 compiler. Kobold2D has these constants to help with the alternative compiling choices.

-(void) dealloc
{
#ifndef KK_ARC_ENABLED
	[super dealloc];
#endif // KK_ARC_ENABLED
}

The acceleratePlayerWithX method adjust the player x velocity keeping it within the maximum limits.

Line 67 is degrading the velocity with the deceleration while increasing it based on the provided input coming from the accelerometer we will see in the update method.

#pragma mark Player Movement
-(void) acceleratePlayerWithX:(double)xAcceleration
{
    // Adjust velocity based on current accelerometer acceleration
    playerVelocity.x = (playerVelocity.x * deceleration) + (xAcceleration * sensitivity);
    // Limit the maximum velocity of the player sprite, in both directions (positive & negative values)
    if (playerVelocity.x > maxVelocity)
    {
        playerVelocity.x = maxVelocity;
    }
    else if (playerVelocity.x < -maxVelocity)
    {
        playerVelocity.x = -maxVelocity;
    }
}

The update method on lines 82 and 83 uses KKInput acceleration smoothedX value to call the acceleratePlayerWithX method. The smoothing helps take out spikes in device data input.

The remaining lines 84 to 108 are positioning the player but keeping it withing the left and right boundaries.

#pragma mark update
-(void) update:(ccTime)delta
{
    // Gain access to the user input devices / states
    KKInput* input = [KKInput sharedInput];
    [self acceleratePlayerWithX:input.acceleration.smoothedX];
    // Accumulate up the playerVelocity to the player's position
    CGPoint pos = player.position;
    pos.x += playerVelocity.x;
    // The player constrainted to inside the screen
    CGSize screenSize = [[CCDirector sharedDirector] winSize];
    // Half the player image size player sprite position is the center of the image
    float imageWidthHalved = [player texture].contentSize.width * 0.5f;
    float leftBorderLimit = imageWidthHalved;
    float rightBorderLimit = screenSize.width - imageWidthHalved;
    // Hit left boundary
    if (pos.x < leftBorderLimit)
    {
        pos.x = leftBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Hit right boundary
    else if (pos.x > rightBorderLimit)
    {
        pos.x = rightBorderLimit;
        // Set velocity to zero
        playerVelocity = CGPointZero;
    }
    // Move the player
    player.position = pos; 
}  
@end

Lesson 2 ==>