Making a scoreboard

I don't know what question 9.69 is or how exactly the code looks (I am looking at asteroids-3 right now, so the counter is already there, just not functional). You have the space, the rocket, bullets and asteroids. The world instance should create and add a counter to the world (to itself). It should also keep a reference to this counter. Then, when you want to add points to the counter (e.g. a bullet hits an asteroid), you get the reference to the counter from the world and add one point to the counter.