To those thinking its a bit simple... You are probably still very early on in the game.
It begins to very quickly increase the capabilities of enemies, negating your ability to use a single 'tranq everyone' to clear things.
They start you with baby steps, because this is one of the most complex games I've ever played, in terms of game mechanics that are occurring at the same time and all have an effect on each other. Play testing must have been a nightmare!
Well done Kojima, for sure a masterpiece.
I've just started finding this...
The enemies are starting to wear helmets making head shots a bit tougher from behind. I've also been enjoying setting off explosives and watching all the red dots on the map scatter and regroup in many different ways. It's amazing!