Well..
I did not think it was as bad as renegade said. It does need some work. Here are some suggestions.
1. The weapons reload/recover way too slow. If you overheat the machine gun you are toast because the two other weapons are pretty much useless. But then again if it takes you 30 seconds to reload a rifle you probably wouldn't survive.
2. THe health indicator is way too busy. It can be hard to tell what health you really have remaining without taking your eyes off of what you need to be focusing on.
3. The enemies are unintersting and are only a challenge because your weapons suck.
4. There doesn't seem to be a learning curve in the game you are just kind of thrust in. Try giving us at least a level or two to ramp it up. Also it is generally accepted that you can see the enemy before they start killing you. These guys just kind of appear.
5. As far as I could tell there aren't any upgrades to either your weapons or your skill using them. That just makes the weapons seem to suck worse.
I think it is a fun concept and could be a good game, but I do think you need a deal of work before it is actually fun. Hope to see a version 2 that is a bit better at some point. I did give you more points than I normally would because the music you chose was beautiful. and true to your intent the game didn't seem to lag at all.