I wasn't expecting too much from something this early in development, but I had a lot of fun!
A lot of these suggestions are kinda nit-picky, and I don't know your current plans, but here they are:
1) Can you put in a map feature at some point? It took me awhile to find the second floor because I couldn't remember where I haven't looked yet, and sometimes got disoriented.
2) A tap-and-hold feature to move continuously until released. This is more laziness on my part though.
3) A zoom function. My screen is averaged sized, but my fingers are kinda thick. It makes it kinda hard sometimes to tap/swipe the enemy since my finger takes up a decent portion of my screen.
I really liked pretty much everything else. The UI is really nice and the controls are easy. I also like how food respawns. I've subscribed to your blog, and I look forward to future updates.
Edit 1: Will you be charging for the final product? I'm having a lot of fun, so I'd definitely pay for it, within reason of course.
Edit 2: I really like the QR code download thingy. Keep doing that!