That's a bare bones description of the game, it's actually more complicated than that. While it does start out pretty simple in all aspects, the game gets progressively harder the further you advance. You start out with your trusty pistols and an unlimited supply of ammo. Along the way you'll pick up better weapons, like the shotgun and uzis, as well as two sizes of first aid kits. Early on your pistols should be more than enough.
Problem is that some items needed to progress in the game are hidden in much the same way.
Another place many gamers found trouble is with the multi-part jumps. Many of these required right on timing, some were timed, and there was one that was next to impossible. That one can be found in level nine, the Cistern. There is absolutely no margin of error in it. Unless you're perfect, reload the saved game.