First off, it was unclear to me that the giant text on the ground was instructions. Maybe if it was a little smaller or something. It took me two (fairly quick) attempts at a run before I realized they were there.
I don't know how much content was in this game as I kept dying not to far into each run, so I'm not sure if there were more bullet hell like enemies that came later, but the basic zombies weren't very bullet hellish.
My frames dipped whenever the upgrade UI showed up. Like as it faded in the framerate was low but after that it was fine.
The different weapons were neat too but switching between them all was a bit weird feeling; I wasn't sure if I really needed to as the guns felt equally powerful and the saws felt much better than either guns. Maybe it would have been good if each weapon went on a cooldown when you use it too much. That way you'd be forced to switch weapons.
The graphics are good looking. Aside from the lack of a clear attack from the enemies, everything looked and felt nice. The movement was the right amount of awkward and responsive. I think it fit the optional theme nicely. It was just fun to slingshot the guy; especially with the saws equipped.
Overall a pretty polished game. Again, the movement was a fun mechanic.