cocos2d shadow

@interface AMSprite ()
@property (nonatomic, strong) CCSprite *shadowSprite;
@end

@implementation AMSprite

- (void)addShadow {
  if(self.shadowSprite) {
    return;
  }
  self.shadowSprite = [CCSprite spriteWithSpriteFrame:self.displayFrame];
  [self.shadowSprite setOpacity:255 / 4];
  [self.shadowSprite setColor:ccBLACK];
  self.shadowSprite.anchorPoint = ccp(0, 0);
  self.shadowSprite.scaleY = 0.5;
  self.shadowSprite.position = ccp( 0, 10);
  [self addChild:self.shadowSprite z:-1];
}

@end