In order to get money quick, buy out and max out the turrets before a wave starts. When you fail, you can sell the turrets then fail the level. You get the money and the turrets come back to be sold again!
It would be really nice to be able to kick players who are abusing the clock. I've played several games, now, where the person runs the clock out, and the auto-kick timer EVERY turn. Really annoying.
I would have liked to see some sort of fireball that continued on a straight path like the enemy had. They were just annoying. Good concept, but the game was long and dull.
It would be good if the ratio of rocks/planets was proportional to your size. Right now, there are a few rocks, and a TON of HUGE planets that trap you. God forbid you get close to two or three planets in the beginning...game over. I can't give you better than a 1, even though it's a great game. Keep working on it.