An entertaining shooter
Everyone says that zombie games are overused, and although I agree, I still enjoy them. This game has been fun from start to finish, especially with all the different weapons and items. If your goal was to create a zombie shooter with tons of enemies on screen while maintaining stable gameplay, I'd say you accomplished it and then some.
I do have two little things to ask:
Given the level of technology as well as the name of the game, isn't Brunhilde more dieselpunk than steampunk? This is just a nitpick, but not many people know of dieselpunk anyway.
Also, is the music available anywhere? It's by far one of the best things about this game, so I'd love to get my hands on it if it's possible.