LÖVE

I was able to play single player that time, very nice job.

A few notes:

• I was able to walk off the map when moving upwards. Might be good to add some kind of bounding box.
• The zombies seem to only move directly at me. The best thing you could do is implement some sort of a* algorithm, but what I've noticed is a quick and dirty method is to say this: If there is a collision between the enemy and the user, check the path along the x and y axis, and then the y and x axis respectively, If the first fails, send them along one of the alternative paths.

I haven't added a bounding box yet, it's not my top priority, I've been thinking about a pathfinding solution for zombies, but I don't know where to start