I really hate when I accidently press ESC, it goes to main menu, and I can only continue from last save, not from where I was, when I pressed the button. It's about the 30th time I press it.
The game should be ok, actually it is pretty fun, till the point, where controls start to stuck, and the whole game lags. The lag is huge, if there are more than 2 zombies, then it is horrible. Please do something about that.
@Arkshija - the reason to pay, is because you spend hundreds of hours enjoying a game, and the author spent probably the same to create it. I am pretty sure, you would not work for free. And the extra content you recieve is enormous. Worth it...
Really fun game, should get badges ASAP, although it is not the hardest, so possibly medium badges would be perfect for it. Next part should be map creator :D