COCOS2D Scoring Help (stackoverflow.com)

// Import the interfaces
#import "HelloWorldLayer.h"
#import "SimpleAudioEngine.h"
#import "GameOverScene.h"

// HelloWorldLayer implementation

NSMutableArray *_targets;
NSMutableArray *_projectiles;

@implementation HelloWorldLayer

+(CCScene *) scene
{
    // 'scene' is an autorelease object.
    CCScene *scene = [CCScene node];

    // 'layer' is an autorelease object.
    HelloWorldLayer *layer = [HelloWorldLayer node];

    // add layer as a child to scene
    [scene addChild: layer];

    // return the scene
    return scene;
}
-(void)spriteMoveFinished:(id)sender {
       CCSprite *sprite = (CCSprite *)sender;
    [self removeChild:sprite cleanup:YES];
        if (sprite.tag == 1) { // target
        [_targets removeObject:sprite];
    } else if (sprite.tag == 2) { // projectile
        [_projectiles removeObject:sprite];
    }
}
-(void)addTarget {

    CCSprite *target = [CCSprite spriteWithFile:@"sprout.png"
                                           rect:CGRectMake(0, 0, 40, 40)];

    target.tag = 1;
    [_targets addObject:target];
    // Determine where to spawn the target along the Y axis
    CGSize winSize = [[CCDirector sharedDirector] winSize];
    int minY = target.contentSize.height/2;
    int maxY = winSize.height - target.contentSize.height/2;
    int rangeY = maxY - minY;
    int actualY = (arc4random() % rangeY) + minY;

    // Create the target slightly off-screen along the right edge,
    // and along a random position along the Y axis as calculated above
    target.position = ccp(winSize.width + (target.contentSize.width/2), actualY);
    [self addChild:target];

    // Determine speed of the target
    int minDuration = 1.5;
    int maxDuration = 4.0;
    int rangeDuration = maxDuration - minDuration;
    int actualDuration = (arc4random() % rangeDuration) + minDuration;

    // Create the actions
    id actionMove = [CCMoveTo actionWithDuration:actualDuration
                                        position:ccp(-target.contentSize.width/2, actualY)];
    id actionMoveDone = [CCCallFuncN actionWithTarget:self
                                             selector:@selector(spriteMoveFinished:)];
    [target runAction:[CCSequence actions:actionMove, actionMoveDone, nil]];


}
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event {
    UITouch *touch = [touches anyObject];
    CGPoint location = [touch locationInView:[touch view]];
    location = [[CCDirector sharedDirector] convertToGL:location];
    //
    [[SimpleAudioEngine sharedEngine] playEffect:@"pew.wav"];
    //
    CGSize winSize = [[CCDirector sharedDirector] winSize];
    CCSprite *projectile = [CCSprite spriteWithFile:@"projectile.png"
                                               rect:CGRectMake(0, 0, 20, 5)];
    projectile.position = ccp(20, winSize.height/2);
    //
    int offX = location.x - projectile.position.x;
    int offY = location.y - projectile.position.y;
    //
    if (offX <= 0) return;
    //
    [self addChild:projectile];
    projectile.tag = 2;
    [_projectiles addObject:projectile];
    //
    int realX = winSize.width + (projectile.contentSize.width/2);
    float ratio = (float) offY / (float) offX;
    int realY = (realX * ratio) + projectile.position.y;
    CGPoint realDest = ccp(realX, realY);
    //
    int offRealX = realX - projectile.position.x;
    int offRealY = realY - projectile.position.y;
    float length = sqrtf((offRealX*offRealX)+(offRealY*offRealY));
    float velocity = 800/1; // 480pixels/1sec
    float realMoveDuration = length/velocity;
    //
    [projectile runAction:[CCSequence actions:
                           [CCMoveTo actionWithDuration:realMoveDuration position:realDest],
                           [CCCallFuncN actionWithTarget:self selector:@selector(spriteMoveFinished:)],
                           nil]];
}
- (void)update:(ccTime)dt {
    NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init];
    for (CCSprite *projectile in _projectiles) {
        CGRect projectileRect = CGRectMake(
                                           projectile.position.x - (projectile.contentSize.width/2),
                                           projectile.position.y - (projectile.contentSize.height/2),
                                           projectile.contentSize.width,
                                           projectile.contentSize.height);

        NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init];
        for (CCSprite *target in _targets) {
            CGRect targetRect = CGRectMake(
                                           target.position.x - (target.contentSize.width/2),
                                           target.position.y - (target.contentSize.height/2),
                                           target.contentSize.width,
                                           target.contentSize.height);

            if (CGRectIntersectsRect(projectileRect, targetRect)) {
                [targetsToDelete addObject:target];
            }
        }

        for (CCSprite *target in targetsToDelete) {
            [_targets removeObject:target];
            [self removeChild:target cleanup:YES];
        }
                if (targetsToDelete.count > 0) {
            [projectilesToDelete addObject:projectile];
        }
        [targetsToDelete release];
    }

    for (CCSprite *projectile in projectilesToDelete) {
        [_projectiles removeObject:projectile];
        [self removeChild:projectile cleanup:YES];
    }
    [projectilesToDelete release];
}
// on "init" you need to initialize your instance
-(id) init
{

    if( (self=[super init] )) {
        [self schedule:@selector(update:)];

        CGSize winSize = [[CCDirector sharedDirector] winSize];
        CCSprite *player = [CCSprite spriteWithFile:@"player.png"
                                               rect:CGRectMake(0, 0, 40, 40)];
        player.position = ccp(player.contentSize.width/2, winSize.height/2);
        [self addChild:player];
        //
        self.isTouchEnabled = YES;
        [[SimpleAudioEngine sharedEngine] playBackgroundMusic:@"techno_loop.wav"];
        _targets = [[NSMutableArray alloc] init];
        _projectiles = [[NSMutableArray alloc] init];
        [self schedule:@selector(update:)];


    }
    [self schedule:@selector(gameLogic:) interval:1.0];
    return self;
}
-(void)gameLogic:(ccTime)dt {
    [self addTarget];
}
// on "dealloc" you need to release all your retained objects
- (void) dealloc
{
    // in case you have something to dealloc, do it in this method
    // in this particular example nothing needs to be released.
    // cocos2d will automatically release all the children (Label)

    // don't forget to call "super dealloc"
    [_targets release];
    _targets = nil;
    [_projectiles release];
    _projectiles = nil;

    [super dealloc];
}
@end