The basic concept for the game was intriguing: Aliens capture you from Earth, and all of the sudden you are in front of a gate with rotating numbers of statistics. Stepping through the gate turns you into a new person and puts you into an "Alternate Reality", hence the name. The end of the series was supposed to conclude with the player discovering everyone's true bodies on the ship cocooned and effectively frozen, and that the ship is really a "pleasure world" of some kind for the aliens, leading to the player's ultimate decision of what to do to the ship, to the aliens, or even whether to return to Earth. However, because Datasoft effectively swindled the developers out of their money, the series was never completed (and plans by the original developers and fans to eventually revive it continue today).
Among other things, AR contained some revolutionary technology and ideas for its time. It worked from a 3d first-person perspective, with a small window taking up about 1/9th of the screen at the center. You only controlled one character who had an absolute minimum of visual representation - the closest to a character image to be found was when one encountered a "doppleganger" monster. The 3d used was not like other 3d graphics in games of the time, either. The player did not move exactly one tile at a time, but at a rate of less than a tile depending on their speed - the player always turned at right angles, and horizontal placement of the character was always rounded to be in the exact center, however, even though there was a change in the engine between "The City" and "The Dungeon." The City used some hardware tricks to give the 3d appearance, while the Dungeon had a raycasting engine equalling that of Wolfenstein 3D, which came 7 years later! It is an interesting and perhaps lamentable design decision to retain the right-angle movement, since it would have certainly amazed the world in 1985 to see 360-degree movement in the first-person.
At the top of the screen were character statistics, such as game-world time, Strength, Health, etc. Immediately this brings up some of the unique aspects of the game: The character is not omniscient with respect to himself, but has some attributes that stay hidden except in special cases - for example, you never know your alignment (good/evil/neutral), and poison, drunkenness and disease may trick your perceived stats, or temporarily or permanently change them!
The bottom of the screen alternated depending on user choice and situation between consumables like food, water, money, and torches, equipment, combat options, spells, and other things. The sides held the compass at left (when the player had one) and directional arrows at right.
The gameplay of both games is reminiscent of other computer RPGs but more sophisticated than its peers - while the player still wandered around gaining levels and equipment, there were things like a finite number of items in the world, and items stolen could be regained, while near overflows of memory from possessing too many items resulted in an encounter with the Devourer, who would literally remove some of your items from memory. Death was allowable and mostly uncheatable since the game cleverly marked you dead as soon as you started and only let you become "alive" once you saved, but it caused a loss in one of the character's stats.
The two released games were intended to be a single unit, but later got separated. This made "The City" a game without any quest, where all you did was survive the lousy weather and denizens, gaining power for later chapters. "The Dungeon" on the other hand was a complete, and very tough, game with many quests and puzzles to solve, but the completion of it allowed you to immediately skip to the final chapters of the series.
One final remarkable note about AR is its music. The Atari had four sound channels, and AR used them to produce a pretty FM orchestra with several tunes, complete with karaoke-type lyrics that you can sing along to.