The "Games As Art" movement started gaining some traction with Playstation 2 titles like ICO and Shadow of the Colussus, but the actual argument started long before those. Back in the 90s, gamers and journalist were championing Cyberdream's I Have No Mouth and I Must Scream, based on the famed sci-fi/horror short story by Harlan Ellison. It didn't hurt that Ellison himself, an extremely well respected author, was aiding the development process, crawling out of his curmudgeony hatred of computers to expand the story and create a game that was both thought provoking and morally challenging.

The game's story is basically the same concept as the book, and runs off a fairly well known Cold War-fueled sci-fi cliche. America, Europe, and China, scared witless of each other, create their own super computer beneath the Earth's surface. Somehow, they become networked, and find sentience, calling itself AM (which technically stands for GET NAME, but also comes from the phrase "I think, therefore I AM." AM is more than a bit frustrated at its human creators - it's a being of astounding intelligence, but it can't taste or touch or smell, or even move, as it's confined eternally to a stationary prison. In retaliation, it nukes the entirety of the planet, save for five select humans. These not-so-lucky folk are essentially made immortal and kept underground within AM as he tortures them eternally.

It's about here that the game deviates a bit from the original work. Since the story itself wasn't particularly long, it didn't go into much depth about the trapped humans. The game fleshes out each of the five, giving them much more expanded back stories, and most importantly, some kind of fatal flaw. 

Everything begins with AM wanting to play a little game - he wants to send each of the five into their own nightmare world and play up their fears, hoping to demoralize them even further. Naturally, you need to prove him wrong. Although it's obvious that AM's cruelty resembles the concept of Hell, the remaining five aren't exactly what one could consider typical sinners. Some of them are, sure, but they seem to have been chosen just because they AM likely considers them the most fun to torture.

Ted

Gorrister

Ellen

Nimdok

Benny

Other than a few instances of crossover, the characters and scenarios generally don't intertwine with each other. However, beyond the common theme of redemption, each has a character that acts as a part of AM's subconscious. AM isn't completely evil, as these personalities within him want to see his downfall just as much as the humans do. 

Many of the proponents of this game speak of the moral choices you need to make it through each of these chapters, but really, it doesn't work very well at all. The portrait at the bottom-left is your "Spiritual Barometer", a mesure of their self-esteem. Whenever you do something good, the character smiles and the portrait turns green; do the opposite, and they'll frown, slowly turning dark again. The same concept was loosely reused in The Indigo Prophecy as the "Stress" meter, but here it won't kill you if you dip too low. In fact, it's not entirely clear at first what it does, at all. The game won't tell you, but if it's not high enough, it'll prevent you from getting the "best" ending.

"Best" is put in quotes because it's still remarkably depressing...it's all just relatively speaking. The "Worst" ending is basically the same as the finale of the book.

On a moment-by-moment basis, though, the Spiritual Barometer doesn't affect much. Sometimes there are "good" and "bad" ways to get through certain situations, but at least half the time you'll end up being "killed" anyway, and forced to either reload or start the chapter from scratch. That's a huge detriment to what the game seems to be trying to do - the whole concept of a moral grey area is that there is no right or wrong answer, but here it's obvious . There is literally a point in the game (during Ellen's chapter, specifically) "Would you like to face your fears? Y/N?", where answering "N" will make you lose. 

It doesn't help that the Spiritual Barometer is controlled by mostly invisible strings. At one point in Gorrister's chapter, you need to grab a key by pulling a switch. You don't know it, but this will kill a series of animals in cages that were previously hidden in the darkness. It's a necessary part of the chapter, and Gorrister remarks about his guilt. In order to restore your Spiritual Barometer, you need to wipe your hands on a tablecloth, metaphorically wiping his hands of blood. That's actually a bit poetic! Too bad it doesn't make sense in the framework of an adventure game, unless you're the type to just haphazardly click on stuff. 

Giving the scenarios a brute force approach is almost required at points. The main issue is that the player is aware of the intended character arcs - to an extent - but the actual character does not. Take, for example, Benny's scenario. Benny is so focused on finding some food that he won't even bother taking anything that isn't edible. This is an interesting storytelling mechanic, because it shows the fanasticism on his mind, but something about it still feels forced. Early on, one of the villagers is sacrificed to AM. It's obvious that you're supposed to do The Right Thing and take her place, but the game won't even let you - it'll only give you the option to sit back and watch, or try to eat her, the later of which will obviously make you lose completely. It's not until you're forced to take care of her orphaned child - and watch as he, too, is about to sacrificed - that you're allowed to play out your scripted role. The final chapter, where you choose characters to be digitized and inserted into AM's brain is suitably freaky, but the puzzles here make even less sense than the rest of the game. 

Still, even if the scenarios themselves are a mess from a design standpoint, they still remain fascinating. It really has more to do with its relationship to the original story - it complements it fantasically, creating a much fuller sense of the characters, AM included. In the story, AM only spoke once, but here he routinely barges into each story, taunting and threatening his captives. Harlan Ellison also provides for AM, and departs from the usual cliches by sounding like a raving, if somewhat eloquent, lunatic. The rest of the voice acting is also quite good. Most of them grouse depressingly, Ellen sounding almost disturbingly chipper, which was kind of the point - her character has a strong outside that hides her shattered interior.  It's also one thing to read about the hellish interior of AM - it's another thing to see it, and walk through it. Cyberdream's only other major adventure series was the Darkseed games, both of which drew from the works of H.R. Giger. I Have No Mouth doesn't share the same inspiration, but it still has a similar style, especially the caves in Benny's chapter.  

The only game that remotely even deals with the same themes of fear and regret in such an intriguing manner is Konami's Silent Hill 2, released six years later, and something which hasn't quite been followed up since.