Buggy, but I didn't see any lag
Level 0 was impossible to get past. The jump was too high. Also, there was no audio sound, other than music. And the Shotgun, which seems to be the focus of the game, does nothing. You can't kill those balls of light. You need to make the objective clear, and fix up the other stuff mentioned above.
Also, NEVER EVER EVER SUBMIT SOMETHING WHEN YOU ONLY WORKED ON IT FOR 35 MINUTES! Especially a game. Games take longer to make than regular flash, therefore more work is required. A flash should be worked on for at least an hour or so before you decide to submit it. A game, I'd say around an hour and a half. And that's the limit. Not that when you work on something for an hour, its all good. That should be your limit.
Also, if you decide to resubmit, then test your game. You may notice some of the errors yourself.