This game is unlike any other reviewed on this website, and that is because there is no other game like it. For starters, Nethack is completely non-commercial; you can get a copy from the game's official website. It is not the product of any established game developer, but rather, the work of various computer enthusiasts. It is a finished, self-contained work, but the developers continually revise the gameplay, and have been doing so over the course of twenty years. You can bet that new versions will be released in the future, and that these new versions may be drastically different from the current one. Nethack has not been promoted through advertising, nor has it been extensively hyped in any magazines, but it has a huge fanbase, through word-of-mouth alone.

Nethack is exactly what the title says, a dungeon hack. You pick a character class and an alignment, and you're dropped into a big dungeon, which you must then navigate to obtain a certain holy relic. Along the way, you have to battle all sorts of bad guys, using such weapons as bows, swords, and axes, as well as a variety of magic spells. Hey, that sounds like Diablo, right? Well, not really. If you like good graphics, FMV cutscenes, or detailed animations and sprites, this is not the game for you. The visuals of Nethack are deliberately primitive; at their very best, they look twenty years old. The dungeon is divided into little square tiles, and your guy is a little square icon, and so are the enemies and items, and the little square icons slide around the dungeon, and that's how the game is played. And many of the game's hardcore fans actually prefer another mode, in which there are no graphics at all, and the game's world is represented by ASCII symbols. You can see now why this game is non-commercial.

So what is the secret to the game's cult success? Quite simply, Nethack is the most complex dungeon hack in existence. It takes the principles behind games like Diablo, and adds myriad complications to every single one. Let's consider a very simple aspect, the use and management of magic spells. In Diablo, you could find books to teach you magic spells, or you could find scrolls for one-time use of those spells. Well, Nethack has that too, except when you find a scroll, you don't know what it is. The game will give it a randomly generated, meaningless name. So, if you want to find out what the scroll does, you'll have to find a "scroll of identify," except, guess what, you probably won't know it when you find one, because it will have a meaningless name, too. You can just go ahead and use the scroll and see what happens, but for all you know, it might unleash some kind of nasty status effect on you.

The same goes for weapons and armour. When you find a weapon, you can only see what class it's in (e.g. "dagger"). You have no way of knowing if it has any special properties. So, you can find a dagger and equip it, only to find out that it's cursed with some detrimental enchantment. You can't unequip cursed items, however, so if you have the bad luck to equip one, then you're stuck with it until you can find some way to remove the curse. You'll probably die long before you get a chance.

The environment of Nethack has lots of little details that you can interact with. For instance, while wandering around the dungeon, you might find fountains, which you can drink from, or dip equipment into, if you want. If you drink from them, you may be healed, or you may be poisoned, or you may release a bunch of deadly snakes, or nothing might happen, or you might find a valuable item. If you dip a sword into a fountain, the sword may turn into the Blessed Rustproof Excalibur, or it may rust and weaken. The actual outcome is randomly determined, and thus utterly unpredictable.

Consider another example. Every character class in the game has some sort of "deity" that he or she worships. For example, the Valkyrie class worships the Norse god Odin. Now, in the dungeon, you may find altars dedicated to various deities. You have the ability to pray or sacrifice something at these altars. Do this, and your deity may heal you, or curse you. The outcome depends on whose altar you're at and what sort of thing you're sacrificing, but it also has a random component.

You get the idea? In this game, you cannot predict anything. Everything is randomly generated, starting with the layout of the dungeons and ending with the outcome resulting from kicking a door. You see, many doors in Nethack can't be opened normally, but can be forced. Unfortunately, kicking a door may result in a broken leg, or an assault by an angry shopkeeper with an arsenal of powerful spells. But you'll still have to kick some doors in order to progress through the game, which means that you're at the mercy of Chance, no matter what you try to do.

The deterministic aspects of the game are no less arduous. Nethack supposes, realistically enough, that characters get hungry as time goes on. So, your character enters the dungeon with a little bit of food, and from then on, he or she will become increasingly hungry. Go without food for too long, and you become weak, then die of starvation. Eat too much, and you become weak and die of obesity. So not only do you have to find food at regular intervals, you have to eat it at just the right time.

Food is scarce in the dungeon; you can buy some from shopkeepers sometimes, but more often than not, you won't have any. So what do you do? Simple: you eat corpses. When you kill enemies, their corpses are frequently left behind. You can pick them up and carry them in your inventory, and then dine on them at a later date. But don't carry them around too long, or they'll rot and become poisonous. (Of course, poison is next to impossible to cure in this game.) Furthermore, if you carry too many things in your inventory, you'll die from over-exertion.

As you can see, the game can be unbelievably grotesque at times. Despite the graphical constraints, you have the freedom to do almost anything at all. So, if you are so inclined, you can murder hobbits, orcs, and dwarves, and then devour their bodies later. Of course, if you murder anyone of the same alignment as you, your deity will become enraged, and will likely find some way to end your lifespan. That leads to more problems: if you're a lawful Valkyrie, you can't kill hobbits, because they're protected by your deity, but the hobbits can gleefully attack you with no consequences whatsoever.

By now, you should understand the essence of this game. Everything is complicated, everything is deadly, everything is randomized. To top it all off, you only get one chance through the game. Yes, if you get ninety percent of the way into the dungeon and die, you won't be able to restart from where you last saved, and you'll have to start over. This is why Nethack has a reputation for destroying the GPAs of computer science students in various colleges: you can literally play it for years on end and still not beat it. And there, perhaps, lies the reason why this game has continued to evolve for twenty years straight, while dozens of other games have come and gone: it is so extreme, and so intricate, yet so deceptively simple on the surface, that beating it really is an impressive feat of skill, in its own way. One can understand why people would bond over it.

To criticize the complexity of Nethack is to miss the point, because complexity is the whole premise behind this game. However, the game can become very distasteful in some respects (as with the constant eating of dead bodies), the text-based user interface is unwieldy, and the game has no storyline to speak of. Those things aren't drawbacks, in the anti-commercial context of the game, but they may make you wonder if the whole damn thing is worth the time.