Each difficulty level could have a different style of movement. For example, the easiest level would allow for mouse movement. The next hardest would be AstroBattle-style. The next hardest would be in the traditional Asteroids style. The hardest would be in the movement style I suggested in the topic "An Idea for Movement."

Levels are weak. Isn't there another way to make it interesting?

How's this: As the game progresses, the AI gets better. At the beginning they could have some sort of randomness factor that decreases as the game progresses. We could also allow the player to choose their own style of movement according to preference.

we need to keep the controlls the same every time. Imagine playing quake and re-learning the keys every game.

Well Quake has a lot more keys you need to know too.

you get the idea don't you?

Don't get angry As long as the controls are simple and it tells you at the start of the levels, I think it won't matter.

Im not angry at all

That's better than straight up levels. You could have every new enemy (the replacements for those lost in combat) be a little more skilled. You could also have more of them in the arena at once (I'm assuming they'll be able to fly around off screen and stay on radar or something) and give them more accurate or powerful weapons (both would probably be too much)