-(void) tick: (ccTime) dt
{
	//It is recommended that a fixed time step is used with Box2D for stability
	//of the simulation, however, we are using a variable time step here.
	//You need to make an informed choice, the following URL is useful
	//http://gafferongames.com/game-physics/fix-your-timestep/
 
	int32 velocityIterations = 8;
	int32 positionIterations = 1;
 
	// Instruct the world to perform a single step of simulation. It is
	// generally best to keep the time step and iterations fixed.
	world->Step(dt, velocityIterations, positionIterations);
 
 
	//Iterate over the bodies in the physics world
	for (b2Body* b = world->GetBodyList(); b; b = b->GetNext())
	{
		if(bomb)
		{
			if (bomblife > 0)
			{
				b2Body* ground = planet->GetBody();
				b2CircleShape* circle = (b2CircleShape*)planet->GetShape();
				// Get position of our "Planet" - Nick
				b2Vec2 center = ground->GetWorldPoint(circle->m_p);
				// Get position of our current body in the iteration - Nick
				b2Vec2 position = b->GetPosition();
				// Get the distance between the two objects. - Nick
				b2Vec2 d = center - position;
				// The further away the objects are, the weaker the gravitational force is - Nick
				float force = kRADIAL_GRAVITY_FORCE / d.LengthSquared(); // 150 can be changed to adjust the amount of force - Nick
				d.Normalize();
				b2Vec2 F = force * d;
				// Finally apply a force on the body in the direction of the "Planet" - Nick
				b->ApplyForce(F, position);
				bomblife--;
			}
			else {
				bomb = NO;
			}
 
		}
 
		if (b->GetUserData() != NULL) {
			//Synchronize the AtlasSprites position and rotation with the corresponding body
			CCSprite *myActor = (CCSprite*)b->GetUserData();
			myActor.position = CGPointMake( b->GetPosition().x * PTM_RATIO, b->GetPosition().y * PTM_RATIO);
			myActor.rotation = -1 * CC_RADIANS_TO_DEGREES(b->GetAngle());
		}	
	}
}
 
- (void)ccTouchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
	//Add a new body/atlas sprite at the touched location
	for( UITouch *touch in touches ) {
		CGPoint location = [touch locationInView: [touch view]];
 
		location = [[CCDirector sharedDirector] convertToGL: location];
 
		if(!bomb) {
			// Create our static "Planet" - Nick
			b2CircleShape shape;
			shape.m_radius = 0.5f;
			shape.m_p.Set(location.x / PTM_RATIO,location.y / PTM_RATIO);
			b2FixtureDef fd;
			fd.shape = &shape;
			planet = groundBody->CreateFixture(&fd);
			// End Create Planet - Nick
			bomb = YES;
			bomblife = 120;
		}
	}
}