What we need to do now is put in an antagonist. Let's add a ball; in this case, we will just call it BallGreen. Add a projectile and make sure it isn't too big. Set the dimensions to 28 by 28 as we want it to be smaller than the walls so that it can fit and not collide. This is shown in the following screenshot:

Let's also put in a projectile. Add a purple ball, rename it Projectile, and set the Size property to 10, 10, as shown in the following screenshot:

Put the green ball on the screen so that we can now test some of the functions. Your project should look like the following screenshot: