Go

[ijdgaf]

The game's rules are simple, yes. But it's just so damn multifaceted and complicated. Balancing defense versus offense, balancing spreading out large ammounts of territory versus keeping pieces close together and defensible... if you play enough, you'll notice you improve in spurts. You'll master a concept and use it a bunch, but then you go up against a better player and realize you're still just an ant at this game.

A lot of players (particularly in Asia) take lessons just like they would for a musical instrument. Don't let the simplicity fool you, it's a very complicated game.