Dwarf Fortress is an amazing game. I mean "amazing" at the level of Sim City and Civilization, as amazing to encounter today as they were when first released. I'm not sure I can offer higher praise.
And yet--it is also frustratingly difficult to get into, and utterly obtuse in terms of its UI.
Dwarf Fortress is a game from an alternate universe. Clearly, no one in his right mind would have created it in our own. I deduce this from its main characteristics, and I think can very clearly describe the alternative universe it came from--let us call it "Earth B."
In Earth B, there never was a revolution in computer graphics, all games are ASCII; and VGA was never invented.
In Earth B, Moore's Law has progressed just as it has in our own, so that most computers now have multi-gigahertz processors.
In Earth B, computer games have existed since the inception of the computer revolution, as on our own world; but lacking the need to spend the vast bulk of their processing power pushing pixels to display pretty images on the screen, game developers have instead harnessed their power to produce incredibly detailed and sophisticated simulations that are presented to the players thereof entirely in ASCII.
In Earth B, Crawford's 1980s claim that "process intensity" rather than "data intensity" was the future of games has been brought to fruition, and Dwarf Fortress is an example--this little 5 megabyte application spends tens of minutes of processing time building the world you play in, rejecting multiple worlds as not being sufficiently balanced to play effectively -- and consuming virtually all of the cycles of your modern, high-end device as it does so, as you can readily see by how slowly other open applications respond while it's world-building -- even though all it's doing is processing, not throwing polygons onto the screen.
So far so exciting, but Earth B has its problems as well. On Earth B, possibly because graphics never evolved as they have on our world, there don't appear to be any common interface conventions. HCI and UCD have never evolved, and every application has its own bizarre interface. Moreover, computer games are apparently still limited to a small audience of enthusiastic, highly intelligent computer geeks for whom no learning curve is too steep. This game doesn't have a steep learning curve; this game throws you against a cliff that you must navigate with the expertise of a seasoned rock climber. Don't even try to play this game without first reading "Your First Fortress" on dwarffortresswiki.net (yes, its fans are so fanatic they've put together a wiki on how to play).
So... What is it?
Dwarf Fortress is a sandbox-style sim game in which you control a party of dwarves in a fantasy world, working to build a new dwarven settlement. Starting with seven people and a handful of supplies, your job is to build a dwarven city, attracting new immigrants and growing through your own internal birthrate. There's no win condition, but it's damned easy to lose--either through bad management, or through any of the various disasters that can easily happen to you, from goblin conquest to flooding of your fortress.
One of the game's slogans, in fact, is
"It's fun to lose" "Losing is fun." And you'd better adopt that attitude, since you will, often.
Let's start with the world. Dwarf Fortress generates a huge world, complete with terrain, continents, and bodies of water. It generates it in 3D too--not "3D" as in "here's a mountain," but 3D as in "we track everything in this world not just at the surface, but at many levels below it as well"--reasonably, since your dwarves, and you will be building mainly underground, and your success depends not only what's on the surface, but on what lies below it too. "Jungle at the top" is only one datum, but "silver ore at level 6" may be more important.
It populates that world with a variety of civilizations you may encounter during play, including goblins and humans. Goblins seem to be innately hostile, but humans you can co-exist with, if you're careful.
Initial play is much like playing an RTS; your basic resources are stone (of many different varieties) and wood (ditto), which you get by mining or cutting timber. Your immediate task is to build an infrastructure that can keep your dwarves in decent comfort: places to store resources and the things you build from them, a barracks, workshops for the essentials (like a carpentry workshop to make beds, and a mason's workshop to build stone doors and tables), a dining hall. Then you'll need to build something to generate food, which is non-trivial; dwarves farm underground, and you need to have a way to irrigate your underground farms from nearby bodies of water. And of course dwarves can survive on water, but it doesn't make them happy; to keep your population satisfied, you need to start making beer right quick.
Every dwarf's skills and characteristics are tracked individually, and having the right mix of skills at game start is critical; the game allows you to micromanage at fair detail, including excluding some dwarves with more critical skills from the toting and lugging activity that winds up being a lot of the work they need to do. But later on, you won't have the time or inclination to micromanage--it feels a bit like Masters of Orion in both its offer of the ability to micromanage and its "bait-and-switch" that says "but you don't want to."
You never give orders to individual dwarves, however; instead, you establish tasks you want done, and hope that the AI's priorities relate to your own at least somewhat, and if not, look for ways to take less-vital tasks out of the queue.
Traders show up at your fortress entrance, often with vital things to offer, and you really need to build the infrastructure to produce trade goods for the things you need; other civilizations discover you, and more likely than not, try to crush you like a bug, and if you haven't built your fortress with defensible choke points and lots of traps, and haven't invested in arms and armor and military skills, well, perhaps your ancestors will welcome you in Valhalla, but in "this" world, you'll likely be restarting from scratch.
Contrariwise, if you're doing extremely well, you can try your hand at exterminating the evil goblin scum yourself.
Oblivion and Grand Theft Auto do a good job of creating the sense that there's a living world that goes on beyond what you see on the screen, that you're a mere part of a world with a life of its own? Yes, they do. But so does this bizarre little pure-ASCII title with its own fanatic following. I've barely scratched the surface of the detail and complexity it offers, in fact.
Someone should take this game, surgically attach some serious UI gurus to the hips of the developers, introduce them to the concept of a tutorial, plow in fifteen million bucks, and...
And, oh well, increase the audience for this game by an order of magnitude, and probably still lose their shirt. The mass audience still wants eye candy over gameplay.
So let Dwarf Fortress be what it is, then; a cult classic, a game that challenges its players to master its abstruse (nay, obtuse) interface and its difficult learning curve, holding out pleasures that only an elite few will ever experience, but in doing so, pointing to a type of gameplay that one can imagine as utterly dominant in some alternate universe, where clever use of processing power, and not processor-intensive graphic gimmickry, is the dominant aesthetic among those who prize games.