@implementation MainPlayScene
{
    CCPhysicsNode *_physics;
    CCNode *MyPhysicsBody;
    CCNode *bottomBody;

}

+ (instancetype)scene
{
    return [[self alloc] init];
}

- (instancetype)init
 {
 // Apple recommend assigning self with      supers return value, and handling self not created
    self = [super init];
    if (!self) return(nil);

    _physics = [CCPhysicsNode node];
    _physics.debugDraw = YES;
    [self addChild:_physics z:1];

 /// BOTTOM
    CGRect bottomRect = CGRectMake(0, 0,      [CCDirector sharedDirector].viewSize.width, 10);
    bottomBody = [CCNode node];
    bottomBody.physicsBody = [CCPhysicsBody bodyWithPolylineFromRect:bottomRect     cornerRadius:0];
    bottomBody.physicsBody.collisionCategories = @[@"Bottom"];
   bottomBody.physicsBody.type =     CCPhysicsBodyTypeStatic;
    [_physics addChild:bottomBody];

  /// MyBody to bounce around
    MyPhysicsBody = [CCSprite spriteWithImageNamed:@"MyBody-64x64-24.png"];
    MyPhysicsBody.position = ccp((self.contentSize.width/2),(self.contentSize.height/2));
    MyPhysicsBody = [CCNode node];
    MyPhysicsBody.physicsBody = [CCPhysicsBody bodyWithRect:(CGRect){CGPointZero,  MyPhysicsBody.contentSize.height,MyPhysicsBody.contentSize.width} cornerRadius:0];
      MyPhysicsBody.physicsBody.collisionCategories = @[@"MyBody"];
    [_physics addChild:MyPhysicsBody z:150];

    self.userInteractionEnabled = YES;
    return self;
}

- (void)touchBegan:(UITouch *)touch withEvent:(UIEvent *)event
{
    CCLOG(@"Touch Detected");
    [MyPhysicsBody.physicsBody applyImpulse:ccp(0, 300.f)];
}

/// try onCollisionEnter first ... nothing
-(void)onCollisionEnter:(CCNode *)entity collisionPair:(CCPhysicsCollisionPair *)pair
{
    if ([entity.physicsBody.collisionCategories  isEqual: @"Bottom"]) {
        CCLOG(@"Hit bottomBody");
    }

}

/// try ccPhysicsCollisionBegin pair ... nothing
-(BOOL)ccPhysicsCollisionBegin:(CCPhysicsCollisionPair *)pair MyBody:(CCNode *) MyBody Botton:(CCNode *)Bottom
{
     CCLOG(@"Hit bottomBody");
     return TRUE;
}

_arrow.physicsBody.collisionType = @"arrow";
_obstacle.physicsBody.collisionType = @"obstacle";

-(BOOL)ccPhysicsCollisionBegin:(CCPhysicsCollisionPair *)pair arrow:(CCNode *)arrow obstacle:(CCNode *)obstacle
{
    // Do some cool stuff
    return TRUE;
}

_physics.collisionDelegate = self;