The concept is really unique, using the time as resource is really cool, love it.
Few things I would improve:
- Title card, don't know if its intendet but it looks like WordArt from old Microsoft Word :D
- increase the background resolution
- improve text resolution
- use a simple color palett fo
- use a different font for the text. there are some great pixel fonts.
- The shooter (the thing that moves from left to right) is kind of flotting in the infront of the frame, mabye give it something it moves on
This are mostly visual improvements, but the game idea is really amazing, keep working on it! :)