Good gameplay, but becomes too hard afterwards
I do enjoy playing this game, the fact that you can adjust your upgrades puts some strategy into it.
But after level 17 and onwards, the game seems to become too difficult. I mean, trying to hit the martians when their too high up makes things hard. Ad when lots of ships are together, you tend to lose a lot of health when attacking, and even more while hanging in the air. Plus the only way to attack is to ram and swipe your tail, which is difficult sometimes when using only the mouse. Maybe add a few more ways to attack, like the spout, and lessen the amount of attacks enemies do, especially the aliens. I can never seem to evade them or their attacks.
Other than those complaints, this is a good game. Keep up the good work.