神経系に訴えかける同意ボタン http://youtu.be/JfzJ_RkizIo

ViewController.m

@interface ViewController ()

@property (nonatomic, weak) IBOutlet UIButton *button;

@end

@implementation ViewController

- (void)viewDidLoad
{
  [super viewDidLoad];
	
  [self blink];
}

- (void)blink
{
  NSTimeInterval duration = arc4random() % 5 / 10;
  
  CABasicAnimation *color = [CABasicAnimation animationWithKeyPath:@"borderColor"];
  UIColor *fromColor = [UIColor colorWithCGColor:self.button.layer.borderColor];
  color.fromValue = (id)fromColor.CGColor;
  UIColor *toColor = [self randomColor];
  while ([toColor isEqual:fromColor]) {
    toColor = [self randomColor];
  }
  color.toValue   = (id)toColor.CGColor;
  self.button.layer.borderColor = toColor.CGColor;
  [self.button setTitleColor:toColor forState:UIControlStateNormal];
  
  CABasicAnimation *width = [CABasicAnimation animationWithKeyPath:@"borderWidth"];
  width.fromValue = @(self.button.layer.borderWidth);
  width.toValue   = @(arc4random() % 5 );
  self.button.layer.borderWidth = [width.toValue floatValue];
  
  CABasicAnimation *radius = [CABasicAnimation animationWithKeyPath:@"cornerRadius"];
  width.fromValue = @(self.button.layer.cornerRadius);
  width.toValue   = @(arc4random() % 5 );
  self.button.layer.cornerRadius = [width.toValue floatValue];
  
  CAAnimationGroup *both = [CAAnimationGroup animation];
  both.duration   = duration;
  both.animations = @[color, width, radius];
  both.timingFunction = [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionEaseInEaseOut];
  
  [self.button.layer addAnimation:both forKey:@"color and width"];
  
  dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(duration * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
    [self blink];
  });
}

- (UIColor *)randomColor
{
  // https://gist.github.com/r3econ/9772706
  
  // 0.0 to 1.0
  CGFloat hue = ( arc4random() % 256 / 256.0 );
  
  // 0.5 to 1.0, away from white
  CGFloat saturation = ( arc4random() % 128 / 256.0 ) + 0.5;
  
  // 0.5 to 1.0, away from black.
  CGFloat brightness = ( arc4random() % 128 / 256.0 ) + 0.5;
  
  return [UIColor colorWithHue:hue
                    saturation:saturation
                    brightness:brightness
                         alpha:1];
}
@end