Dwarf Fortress is a single-player fantasy game. You can control a dwarven outpost or an adventurer in a randomly generated, persistent world. The world is randomly generated with distinct civilizations spanning over 1000 years of detailed history, dozens of towns, hundreds of caves and regions with various wildlife. Command your dwarves as they search for wealth in the mountain. Play an adventurer and explore, quest for glory or seek vengeance. Extended ASCII character set rendered in 16 colors (including black) as well as 8 background colors (including black). Although Dwarf Fortress is still in a work in progress, many features have already been implemented. Please post all support issues in the forums for the game.
Excellent, very complicated roguelike game with impossibly deep world. Has a problematic controls that require some time to accustom, yet after some time, one will have no problem with controlling all dwarves.
Of course, you don't need to play in ASCII, there are many neat graphic packages that make game a little less raw.
Game has both - strategy and ADOM-like roguelike mode, so anyone will have what likes.
And for final, a quote about gameplay...
"I caught a vampire too. A fisher-dwarf accused the expedition leader, who I knew was innocent of course. So I had my sheriff drag the fisher-dwarf to the dungeon. I had no hammer, so he had to wait to be executed while we forged one. After 50 hammer strikes I knew I was right, because he lived."