Oh yeah. That screenshot looks like the brain fart of your old DOS computer, doesn't it? Funnily enough, this shot captures a lot of what makes Dwarf Fortress so complex and, by extension, addicting. As you might be able to guess, the right side of the screenshot is an overhead two-dimensional representation of the fortress. Those are rooms, dining halls, armories, warehouses and more. The icons depict different things and, remarkable as it may seem, playing the game enough allows you to recognize them fluently. While you may not be able to, I can see the bedrooms of various dwarves, I can see the room with casks of ale. I can see beds, tables, foundries, ore, engraved walls, and on and on. Some icons are easier to guess the meaning of than others. For example, the two big arrow symbols pointing outside are ballistas ready to be fired. All of the smiley faces are dwarves. Outside, you can see on the far left the curve of a river, the bridge over it, and the road leading to the fortress entrance.
Long story short, this is a game that manages to find a truly insane amount of depth and complexity by using the most basic graphics imaginable. By setting the bar for graphics so low, it permits a massive amount of resources to be dedicated to the most crazy awesome things you can think of. Your dwarves can all be equipped, clothed, given rooms and tasks unending. They can make friends and gain skills that make them more (or less) useful to the running of the fortress at large. As for the fortress, you can construct traps, pump-driven systems, smithies, forges, farms, and more. You can conduct trade with visiting merchants, distant elf nations, and go to war with goblins, undead, and even homicidal elephants. What is perhaps so addicting about this game is that it is basically a medieval/fantasy SimCity to the most complex (yet definitely learnable) and hilarious degree.
Bird's eye view of a fortress
I say hilarious because there are no win conditions. Part of the fun is seeing how far and how long you can go before the fortress collapses due to domestic strife, outside intervention, or even inadvertently digging too deep and opening a corridor to Hell. One of the times I played, some asshole accidentally killed the cat of my most deadly swords-dwarf. He hunted down and killed the offender. When the police-dwarves stepped in to arrest him for the murder, they proved unable to, and he swiftly killed them too. A growing cycle of violence quickly consumed the entire fortress as family members got pissed and swore bloody vengeance. In time, the swords-dwarf was killed, but too much violence had put internal affairs on pause for so long that the survivors all starved to death. All the children were stolen away by nearby monkeys. Not kidding. All of this started because some prick accidentally stepped on a cat.
It can require a dark humor to get entertained by this, but it gets to the point where your management skills cannot counter or keep up with the chaos that the game can present you with. A flood can throw off your construction plans. One dwarf might get jealous of another, causing dissent that you must prepare for by having an established system of justice (or by straight up assassinating the guy). The game is tough and it requires planning, but it is planning of a sort which doesn't frustrate so much as make you consider what you might possibly do to work around it. Example: goblins show up, you barricade the doors. How do you solve this problem? Well, you don't have to if you work on attaining self-sufficiency within the mountain. Alternatively, there might be a plateau reachable from another level that the goblins can't reach but you can, allowing you to plant farms and reach the outside world that way (or even snipe down at the goblins with crossbows). You could send out your combat-capable dwarves to fight them, you could create an alternate entrance that is actually filled with traps for the goblins to run into when they see a new open door. Or, hell, if you're really determined, you could dig deep, find a lava flow, and create a pipeline to dump magma right on top of their heads!
The sheer creative possibilities and the massive options before you is what persuaded me that I had to stop playing Dwarf Fortress. It brings out a sadistic inner architect and social experimenter that can never be satiated. It makes me want to hurl myself into it again and again to build ever more intricate and interesting fortresses and to see how many dwarves I can take care of and keep safe (or domineer) before the system falls apart. But, even though I've banned myself from playing it, I've still been plenty entertained by the stories of others who do.
For a brilliantly depicted example of an entertaining game of Dwarf Fortress, consider checking out this link. It'll send you to a site that tells the story of one particular fortress where players would switch off for every in-game year, each different player having different projects and different things happen to them until the fortress' inevitable doom. Things such as a dwarf-elephant war, accidental drownings, and fights over who gets the best crypts. It's hilarious and definitely worth checking out if the game intrigues you, but not enough to get sucked into the addiction first-hand!