Dont worry farmer I wont hurt you, it is not unheard of for someone to have lived in a cave for a decade. It is my duty to destroy your ignorance!
DF is a ASCII game that focuses on you building a dwarven settlement from scratch with 7 dwarves and surviving/building into a massive kingdom with hundreds of dwarves.
Its extremely complex and hard to master the basics, but the nice thing is because of that you can actually invent stuff in the game unlike others were you are trapped with making pre-set buildings. One of my favorites was one person getting bored, so he built massive pillars to hold up a "ceiling" above his entire region, then used channels and trap doors to gather the rain water into an underground lake. It is a lot more epic than it sounds.
Then there is building traps with magma which has practically become an art at this point. The game does have liquid pressure, so you can build a pipe system that lets you shoot balls of magma down a hallway at enemies.
Here is a screen-shot of a fortress in-game, although this is a very, very small fortress, unless they had a larger dining hall on another level which I doubt. Most likely spent only and hour or two on building this. (After getting good enough to not flood my own fortress and killing everyone I had some forts with weeks of gameplay time on em.)
Fortress Pic
Like I said the game is very complex and I am not even scratching the surface of everything you can do in the game. It would take me ages to explain everything, so, if you enjoy RTS games go ahead and try this out.