Well, dang, we can't have that. It consists of four chapters divided into levels with specific objectives. Normally that is survive to find the exit, but that isn't always the case. Genocide is as in fact pretty simple. Monsters are generally passive, won't follow you around, can't shoot very straight and don't hit for much damage.
Suicide is quite the opposite.
While the AI isn't super fantastic, the monsters will take evasive action, run away at times, and can deliver some brutal damage if you aren't on your toes. In addition to the difficulty levels, you can choose to play either as Caleb or one of the other three members of the Chosen. Each has varying speed, health, weapons skill and dark magic powers. Caleb is perhaps the most well rounded, he's the default choice. Controlling the action is pretty standard for a first person shooter.