I don't mean it in a bad way at all. I just want to know how long this game is exactly. I'm enjoying it tremendously but I'm having trouble finding a reason to play any of the optional missions, leveling up my weapons, building bases, etc.

I know the story has 5 chapters and I'm already on 3 so I'm just wondering if I should be doing any of the extracurricular stuff. Does the game become to hard if you try to play it with weak weapons and no R&D?

Any input from people who've finished it is greatly appreciated.

The bosses can be pretty tricky if you haven't levelled up your weapons or have some sort of rocket launcher, but for most levels just stick with the tranq gun and you're sorted.

You have to do some side stuff later on to get the last bit of story. A lot of people ended up missing the actual end to the game because of this. I would describe what missions they are but they're pretty spoilery. They involve playing a certain "game" with someone.