Like the music a lot, fits well. Interesting idea to use math, but I didn't understand how the adding/subtracting "E" part worked. I started with a lucky number of 12 and around 123458 as my starting unit. I was able to shoot things and I seemed to be progressing, but then I thought I had to multiply 3x4 in E, instead multiplied my unit number by a lot. Suddenly my unit number was over two million, and I couldn't shoot anything. It seemed like the number was counting down for each bullet fired, and I thought there was no way I would get down to 123887, or whatever it was, to be able to damage enemies again. So, I'm not sure what the mechanic there was.