good game, but leveling up and healing systems do not work: at the start you're barely holding up, but every kill grants you a level up, which restores all hp. Once you reach the maximum level, you get a fixed amount of hp per every kill, which is not enough to refill all of the health. Since the environment suddenly changed, player doesn't know what tactic to choose and the game becomes too hard.
Could you, please, fix your progress curve?