Please, make Black Keys possible to get, thats ridiculous. Is easiest to win in some lotteries than find a key. I know you NK professionals don't need this kind of "appeal" to earn our money.
Nightmare was already hard... but now, besides hard it has a chance of being a waste of time, since sometimes the bosses don't drop money or nice loots, only steel loots. Don't mess up with our fun.
Please, remove these super zombies that spawns and kill everyone with a single hit. These things are spawning for low level players. Even together we can not kill them. We're wasting our time playing a long mission, to fail cuz a single super glitched creep.
New features for uses which is able to use their money is necessary. Like VIP account, which gain more EXP and money after each match, Clean UP items, to remove all default items upgrades, etc.
 "SAS: Zombie Assault 4"){kind=icon}