Seems like a good start.
It was funny how the shopkeeper is controlled by arrow keys, so just disable that.
I like the way the fog of war spawns back and that the enemies seem to follow you via the fog of war you removed.
Further, it is a tad difficult to play, it seems the spawn statues just have too much health. Dont' really have the patience to whittle them down for half an hour.
Gold seems plentiful enough, so maybe exploding bullets will solve that problem.
I recommend some sort of icon that shows a currently active upgrade, so the player knows he has them. After dying a few times I couldn't remember if I went to the shop yet, and knowing whether I have crap, or slightly-less-crap bullets would help:)