Interpreted the 5 asset rule to be visible assets (not counting hud, or lighting). All walls count as one, 2 different projectiles, a player, enemies (all the same).
There is really only one rule, which is to kill all the enemies. I suppose another rule is, if you bounce your projectile off the wall, it will do double damage and kill the enemy instantly versus taking to straight hits.
Controls are simple, WASD for movement, spacebar to shoot.
In the future I may add to it and include a multiplayer, I think that would be most fun.