This was really fun. I figured out that you need to skip some weapons to get through a level fairly quickly, but I think it is a nice touch, and with more enemies and weapons this could get really cool. I love the graphics as well, especially the way the zombies look after you heal them. I found one little problem, which is what happens when you heal the big guy like this (you can't get up the ledge anymore:
All in all this was super fun! Well done!