Several times now, no matter what stage, I've encountered enemies spotting me in the way that they know where I am and can shoot me dead with one headshot, even tho I am hiding and there is No way to be seen from the outside. This has also happened and I have also been shot through rocks.
You should really insert a Report-option, because I know people are cheating.
I've seen speed-hacks, god-mode and this see-through-walls things.
Also I've encountered once with a fullt loaded Luger an enemy came in and I could not shoot. Instead of showing number of ammo, I saw a line ( - ) and where the remaining ammo is supposed to be there wasn't even a number. I could not melee either and the enemy knocked me dead with one blow.
This is to bad in an otherwise really Good and unique game.
