What we are trying to achieve can be put into the following two categories:
What we want for the border:
Asteroids, bullets, and the ship need to know when they have collided with the border
Asteroids should reverse and head back into the game area when they touch the border
A bullet should reset itself at the border
The ship should subtract a life and then respawn in the centre
What we want for the asteroids. We need to know and respond when:
The ship touches an asteroid
When a bullet touches an asteroid
As in the original Asteroids game, we will not respond to asteroids bumping into each other
Although we will not be detecting an asteroid on asteroid collisions, you will see that when our collision detection nears completion, achieving asteroid on asteroid collision detection will not present much of an extra challenge. However, it will put extra strain on the device's CPU.
We know that we have object on border collisions to detect and object on asteroid collisions...