Really enjoyed the game, loved the variation, upgrades and simplistic feel - good job :D A few little things:
1. It's hard to see some enemies if they are the same colour as the background, perhaps for a future instalment, make all enemies one type of colour (hot or cold) and have the background as the opposite.
2. The rocks which float around you - could you make them square? Kinda confusing having circle enemies and rocks!
3. Bullet spray types (would be cool to further customise, such as machinegun, shotgun, rockets etc.) Perhaps some levels would require you to switch spray type to order to win.
4. Finally not really for me, but I'm sure other people would appreciate it if you were to make a sequel: an endless mode, where the enemies get slowly tougher and a highscore is rewarded at the end.
I am giving it 2 stars, I gave the last one 5, for reasons such as , ever heard of a distance magnifier? well it obviously doesn't apply to this game,2nd there should be a flip button, 3rd unlike the old game, the bigger things arn't heavier then the small things!