-(void)update:(CCTime)dt
{
    //1
    CGSize viewSize = [CCDirector sharedDirector].viewSize;
    
    //2
    if (_bird.position.x < 0)
        _bird.flipX = YES;
    
    //3
    if (_bird.position.x > viewSize.width)
        _bird.flipX = NO;
    
    //4
    float birdSpeed = 50;
    float distanceToMove = birdSpeed * dt;
    
    //5
    float direction = _bird.flipX ? 1 : -1;
    
    //6
    float newX = _bird.position.x + direction * distanceToMove;
    float newY = _bird.position.y;
    
    //7
    _bird.position = ccp(newX, newY);
}