Level 30 was cool.
I thought it was cool. Some of the later levels had pretty cool designs for the enemy ships. I have but three complaints. Firstly, the game gives you enough money to buy everything by level 15 or so, after which your just buying an unnecessarily large supply of extra lives. Second, you can buy the super homing missile set by around level 5. Maybe you should make all the secondary weapons go in order so you'll be forced to actually use some of them. Or you could just make the later weapons more expensive. My third complaint is just a small irk. The "mine ships" later on are one hit kills. That doesn't bother me, but you should get some sort of warning that those mines are that powerful. I would also like to be able to buy some reverse thrusters.