The overarching feeling in Nethack play, during a given player's mandatory initial period of acclimation and exploration and regular, maddening failure (it lasts a couple of years, get used to it), is being at sea. I played for a few minutes this morning - perhaps a half-hour - and the game's moment-to-moment unpredictability, combined with the sheer number of factors of which Nethack players are expected to keep track, had me in a constant state of feeling overextended somehow. At every step I was certain I'd missed something. Yet when I died (in Minetown, set upon by a band of giant insects after being turned mid-melee into a goddamn wererat, meaning I had to drop every one of my positions just to zap the killer bees with my wand of sleep, et cetera and DYWYPI...) it still came as a total surprise, and I still swore loudly at no one, somehow in that instant retroactively certain that this time I was really gonna win.
That doesn't sound very appealing, does it? Lemme tell you: it's fantastic. Nethack stands as one of the all-time classic video games, for both formal/aesthetic reasons (it's well-wrought, aesthetically coherent and consistent, with an interface unequalled for its richness and multifacetedness) and weirdly, unexpectedly visceral ones. Nethack has no right to be exciting but it somehow is, in a cerebral way that other turn-based games (e.g. Civilization by Sid Meier) manage not to capture. Much of Nethack's addictive appeal stems from the speed at which it moves, of all things. Because the game features a relatively flat set of commands - i.e. for the most part not revealed through hierarchical menus but immediately available at a keystroke or two, as in UNIX text editors - and movement/combat is achieved with a single keystroke, it's possible to build up a real head of steam playing Nethack, to attain an almost real-time tempo and inevitability. The fact that you can pop out of this flow state at any time to mull over options or consult spoilers - info-gathering takes no gametime - grounds you, comforting without undercutting the tension.
The simplicity of Nethack's interface is crucial. Compare the mouse-driven interface to Diablo, which is essentially a real-time graphical Nethack For Dummies centered on combat tactics. Diablo (along with its far superior sequel) requires a system of keyboard shortcuts, because the mouse/menu interface is worse than useless in combat. On the one hand, it's straightforward to customize the Diablo interface to a degree; on the other hand, many functions of the game are several mouse-clicks or keystrokes away. Oddly enough, this puts the gamer in the position of making complicated ritual hand gestures in order to, say, cast a magic spell. This weird interface mimesis enhances the physicality of the game, and since so much of one's mastery of Diablo depends on reaction time and the execution of set physical gestures, the shallowness of its intellectual appeal is more than offset. The Diablo games are (or in any case were, for years) hugely popular; they're good-looking, creepy, and well-scored, and in their online incarnations the tactical nature of combat largely gives way to a resource optimization and trading meta-game, a commodities exchange in digital armour and gemstones that pushes players toward automation and actuarial work. But Diablo is an action game first, and the curiosity is that its appeal rests on an interface plainly ill-suited to its task.
But note also that Diablo's interface lifts its atomic element from Nethack: movement and combat are accomplished with a single click on a given onscreen location. If there's a beastie there, your character will try to kill it; if not, he'll just move to that spot. Diablo can afford its denuded interface because the player character's interactions with the world are so limited: you can pick up things or drop them, and beyond that (with one or two special-item exceptions) clicking means combat or spellcasting. The player knows the world very narrowly. Grand Theft Auto III works similarly, though the popular press seems to mistake that game's size for depth. Nethack's interface is far broader, and the actions it affords far deeper (i.e. actions and objects can be chained in interesting ways), but no action in the game is more than a couple of keystrokes away. Even the special commands, which must be typed out (as nearly all the single-keystroke commands are in use, if you can believe that), are autocompleted, and so take no more than a letter or two to specify. Past the original sensation of interface voodoo, which is bound to strike any player unaccustomed to a screenful of seemingly random ASCII characters and literally dozens of game commands always at her disposal, the Nethack interface behaves logically and affords complex association through an uncomplicated command set.
It's hard to play Nethack with your brain running on low power, whereas Diablo is a bit like Tetris: you can put it on at 3am and more or less approximate the performance of a mediocre player, not because those games are 'easy' but because they have a real-time inevitability that renders sustained reflection all useless anyhow. You won't do well at Tetris at 3am after a night's boozing, but you shouldn't even bother with Nethack; the number of choices you'll face at any given moment will probably paralyze you. Which but that reminds me did I mention? Goddamn paralysis potion I drank on Dlvl2 thinking it was something else, standing in the doorway of a liquor store having just leveled irritatingly up thereby increasing the priest bribe of course, thank Tyr there weren't any nasties about. And earlier this week that priest of Loki waxed me right well after my kitten Pampers utterly failed to do his part cleaning out the Minetown temple during my attempts to convert the altar, siiiigh...