Shit, I remember playing this a long time ago when I first checked out AGDG and gamedev in general. Back then I was a little annoyed at the level design, mostly because I didn't know where to go half the time, but the combat was enjoyable and the story was just compelling enough to stick around and check out all your demos.
Of course I know this demo isn't how the final game will end up (arena style), but cutting out the levels and just having pure combat was really fun! I had to force myself to stop playing after ripping and tearing through enemies with Frank. The neon lights of the projectiles kinda clashes with the rest of the game, and some enemies would get caught in the corner behind the portal, but other than that there's not much to gripe about.
I'm sure the levels will be a bit better now that you have some more experience, so I can't wait to see what you'll cook up in the new engine! Keep it up, mate!