Setting CPU Difficulty for Pong - ios

Question

Second time on here hoping that someone can guide me in the right direction.
I'm trying to implement a Pong game within an app for iOS devices (iPhone/iPod/iPad) and it works just fine, except for the fact that I can't beat the CPU, let alone score a point. Here's the implementation .m code:
#import "BTM_pongGame.h"
#import <QuartzCore/QuartzCore.h>
#define STEP_DURATION 0.05
#define RESET_BALL_ANIMATION_DURATION 0.5f
#define MARGIN_WHERE_BALL_IS_LEAVING 40
//#define CPU_SKILL 20
#interface BTM_pongGame ()
#end
#implementation BTM_pongGame
#synthesize cpuSkill, ballShape;
- (void)viewDidLoad
{
[super viewDidLoad];
cpuSkill = [BT_strings getJsonPropertyValue:self.screenData.jsonVars nameOfProperty:#"cpuSkill" defaultValue:#"20"];
ballShape = [BT_strings getJsonPropertyValue:self.screenData.jsonVars nameOfProperty:#"ballShape" defaultValue:#"1"];
if ([ballShape isEqual: #"1"]) {
self.ball.layer.cornerRadius = self.ball.frame.size.width / 2;
} else {
//self.ball.layer.cornerRadius = self.ball.frame.size.width / 2;
}
}
- (void) wordsPerLineInfoShowAlert {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Choose Game"
message:#"Multiplayer or Single Player? You decide! Choose below."
delegate:self
cancelButtonTitle:#"Single Player"
otherButtonTitles:#"Go Back",#"Multi Player", nil];
[alert show];
}
- (void)alertView: (UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex
{
NSString *title = [alertView buttonTitleAtIndex:buttonIndex];
if([title isEqualToString:#"Single Player"]) {
[self resetPlayerScoreLabels];
[self updatePlayerScoreLabels];
self.mode = kGameSinglePlayer;
[self moveComputerPaddle];
//Disable panning of computer paddle
[self.playerOne.superview setGestureRecognizers:#[]];
[self resetBoardForNewRound];
} else if ([title isEqualToString:#"Multi Player"]) {
[self resetPlayerScoreLabels];
[self updatePlayerScoreLabels];
self.mode = kGameMultiPlayer;
[self resetBoardForNewRound];
} else if ( [title isEqualToString:#"Go Back"]){
[self navLeftTap];
}
}
// thanks to MrsVanBeveren for coding the reset score stuff
-(void)resetPlayerScoreLabels
{
playerOneScore = 0;
playerTwoScore = 0;
}
-(void)viewDidAppear:(BOOL)animated
{
[super viewDidAppear:animated];
[self wordsPerLineInfoShowAlert];
[self startGameTimer];
}
-(void)viewDidDisappear:(BOOL)animated
{
[super viewDidDisappear:animated];
[_gameTimer invalidate];
}
-(void)quitPressed:(id)sender
{
[self dismissViewControllerAnimated:YES completion:nil];
}
-(void)startGameTimer
{
[_gameTimer invalidate];
_gameTimer = [NSTimer scheduledTimerWithTimeInterval:STEP_DURATION target:self selector:#selector(step:) userInfo:nil repeats:YES];
}
#pragma mark Game setup
/*
* Some maths to calculate a new starting direction
* By choosing mid left/right part of the unit circle
* we avoid getting straight up/down directions
*/
-(void)resetBallDirection
{
float randomUnity = arc4random_uniform(100)/100.0;
int horizontalDirection = (arc4random() % 2 ? 1 : -1);
float angle = M_PI_4 + randomUnity * M_PI_2;
float direction = horizontalDirection * angle;
dirX = sin(direction);
dirY = cos(direction);
}
-(void)resetBoardForNewRound
{
speed = self.view.frame.size.width / 50.0;
[self resetBallDirection];
[_gameTimer invalidate];
[UIView animateWithDuration:RESET_BALL_ANIMATION_DURATION animations:^{
self.ball.center = CGPointMake(self.view.bounds.size.width / 2.0, self.view.bounds.size.height / 2.0);
} completion:^(BOOL finished){
[self startGameTimer];
}];
[self enlargeAnimation:self.ball];
}
-(void)updatePlayerScoreLabels
{
self.playerOneScoreLabel.text = [NSString stringWithFormat:#"%d",playerOneScore];
self.playerTwoScoreLabel.text = [NSString stringWithFormat:#"%d",playerTwoScore];
}
#pragma mark Paddle handling
- (IBAction)paddlePanned:(UIPanGestureRecognizer*)recognizer {
UIView *paddleWrapper = recognizer.view;
UIView *paddle = [[paddleWrapper subviews] lastObject];
switch([recognizer state]) {
case UIGestureRecognizerStateBegan: {
paddle.backgroundColor = UIColor.whiteColor;
}
break;
case UIGestureRecognizerStateChanged: {
CGPoint position = [recognizer locationInView:self.view];
CGFloat haldPaddleHeight = paddleWrapper.frame.size.height / 2.0;
CGPoint newCenter = paddleWrapper.center;
newCenter.y = position.y;
newCenter.y = MAX(haldPaddleHeight, newCenter.y);
newCenter.y = MIN(self.view.bounds.size.height - haldPaddleHeight, newCenter.y);
paddleWrapper.center = newCenter;
}
break;
case UIGestureRecognizerStateEnded: {
paddle.backgroundColor = UIColor.grayColor;
}
break;
default:
break;
}
}
#pragma mark Game loop
/*
* Game loop
* - Moves the ball and checks for obstacles
*/
- (void)step:(NSTimer*)timer
{
speed += 0.05;
[self checkForBallLevingSide];
CGPoint newCenter = self.ball.center;
CGFloat ballRadius = self.ball.frame.size.height / 2.0;
newCenter.x += dirX * speed;
newCenter.y += dirY * speed;
CGFloat upperEdge = ballRadius;
CGFloat bottomEdge = self.view.bounds.size.height - ballRadius;
// Bounce ball of top/bottom walls
if (newCenter.y <= upperEdge) {
dirY = ABS(dirY);
newCenter.y = upperEdge;
} else if (newCenter.y >= bottomEdge) {
dirY = -ABS(dirY);
newCenter.y = bottomEdge;
}
[UIView animateWithDuration:STEP_DURATION animations:^{
self.ball.center = newCenter;
}];
}
-(BOOL)didBallHitPaddle:(UIView *)paddle withinLimit:(CGFloat)limit
{
if (CGRectIntersectsRect(paddle.frame, self.ball.frame)){
[self deflectBallFromPaddle:paddle];
CGRect ballFrame = self.ball.frame;
ballFrame.origin.x = limit;
self.ball.frame = ballFrame;
return YES;
} else
return NO;
}
-(void)checkForBallLevingSide
{
float limitLeft = MARGIN_WHERE_BALL_IS_LEAVING;
float limitRight = self.view.bounds.size.width - self.ball.frame.size.width - MARGIN_WHERE_BALL_IS_LEAVING;
CGRect ballFrame = self.ball.frame;
CGFloat ballX = ballFrame.origin.x;
if (ballX < limitLeft) {
if (![self didBallHitPaddle:self.playerOne.superview withinLimit:limitLeft])
[self playerDidMiss:kPlayerOne];
}else if (ballX > limitRight) {
if (![self didBallHitPaddle:self.playerTwo.superview withinLimit:limitRight])
[self playerDidMiss:kPlayerTwo];
}
}
/*
* Calculates new dirX and dirY after the bounce.
* The longer from the paddle's middle the bigger the result angle gets. (Pong style)
*/
-(void)deflectBallFromPaddle:(UIView *)paddle
{
dirX *= -1;
CGFloat diff = self.ball.center.y - paddle.center.y;
float p = diff / paddle.frame.size.height * 2.0f;
dirY += p * 0.5;
}
-(void)playerDidMiss:(kPlayer)player
{
if (player == kPlayerOne) {
playerTwoScore++;
[self victoryShake:self.playerTwo];
[self enlargeAnimation:self.playerTwoScoreLabel];
}
else if (player == kPlayerTwo) {
playerOneScore++;
[self victoryShake:self.playerOne];
[self enlargeAnimation:self.playerOneScoreLabel];
}
[self resetBoardForNewRound];
[self updatePlayerScoreLabels];
}
-(void)moveComputerPaddle
{
UIView *paddle = self.playerOne.superview;
CGPoint cpuCenter = paddle.center;
CGFloat diff = self.ball.center.y - paddle.center.y;
CGFloat movement = MIN((int)cpuSkill, ABS(diff));
movement *= diff > 0 ? 1 : -1;
cpuCenter.y += movement;
[UIView animateWithDuration:0.1 animations:^{
self.playerOne.superview.center = cpuCenter;
} completion:^(BOOL b) {
[self moveComputerPaddle];
}];
}
#pragma mark Animation
-(void)victoryShake:(UIView *)view
{
CAKeyframeAnimation * anim = [ CAKeyframeAnimation animationWithKeyPath:#"transform" ] ;
anim.values = [ NSArray arrayWithObjects:
[ NSValue valueWithCATransform3D:CATransform3DMakeTranslation(0.0f, -20.0f, 0.0f) ],
[ NSValue valueWithCATransform3D:CATransform3DMakeTranslation(0.0f, 20.0f, 0.0f) ],
nil ] ;
anim.autoreverses = YES ;
anim.repeatCount = 4.0f ;
anim.duration = 0.07f ;
[view.layer addAnimation:anim forKey:nil];
}
-(void)enlargeAnimation:(UIView *)view
{
CABasicAnimation *animation = [CABasicAnimation animationWithKeyPath:#"transform"];
animation.fromValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(1.0, 1.0, 1.0)];
animation.toValue = [NSValue valueWithCATransform3D:CATransform3DMakeScale(3.0, 3.0, 1.0)];
[animation setDuration:RESET_BALL_ANIMATION_DURATION * 0.5];
animation.repeatCount = 1.0f ;
[animation setAutoreverses:YES];
[view.layer addAnimation:animation forKey:nil];
}
#end
I've simply tried changing the number where it states #define CPU_SkILL and again #"cpuSkill" defaultValue:#"20"];, but I've had no luck with changing the number in any direction.
Any ideas?
Thank you in advance.

Answer 1

The cpuSkill variable controls the movement of the CPU-controlled paddle:
CGFloat movement = MIN((int)cpuSkill, ABS(diff));
So maybe the cpuSkill is higher than intended in every situation. Try much lower values or make some random little adjustment to movement after the calculation.
Also, you should ABS() the cpuSkill to avoid perfect moving when negative moving.