From what I've played of it (a few hours without finishing it), it's about fighting enemies as efficiently as possible. Killing lots of things doesn't get you anything, but you waste health or resources in the process. When you have to fight something you try to do so as efficiently as possible by of course not missing if you shoot, but also using the knife as much as possible - which is difficult to do without getting hurt - or luring enemies to their deaths in other ways to conserve bullets. Otherwise you avoid fighting at all. This goes similarly for the other resources you are given - bombs, upgrade parts etc. You're never given as much as you would like. I think it's a good game. The learning curve isn't too high if you pay attention but the challenge is there right from the beginning and really ramps up later on. On the other hand maybe you've discovered all this already anyway through lets plays if you've watched those yet. Well, have fun anyway.