Great game. I have some ideas...
Albosulately great game. I could play it all day. I have a few ideas for a third installment.
1) For the mouse movement, force the guy to follow the mouse, instead of having to click on it and drag. It took me quite a while to figure out what was going on at first.
2) Add powerups for the shot. Either give them at specific Evo levels, or have a few bubbles here and there. (Or both, Evo levels strengthen shot, bubbles power up said shot.)
3) Add more enemies, make them move a little. Maybe even add a few that shoot back.
The game was absolutely fantastic, and I hope to see another!
NOTE: My suggestions were entirely based off of easy mode. I didn't play hard, so I don't know if it changes at all.