What's going on is--well, figuring out what's going on is one of the game's few real puzzles, so it won't be revealed here, but suffice it to say that almost no information is given to you initially. The process of discovering who and where you are and what you're doing there is rather deliberate; there's a lot of information to glean over the course of the story, but very little of it is available initially, which makes the game somewhat less immediately accessible than it might be. Contributing to this problem is the world you inhabit, which may fairly be described as alien; there are plenty of unfamiliar names and terms scattered here and there, and while they all eventually either get explained or become obvious, a player could be forgiven for finding the learning curve a bit steep at first.
There's an upside to all the strangeness, however, that comes as the story develops: the player's imagination is freed to an extent it might not be if all the quantities were initially known. The flora and fauna you discover, for example, are given primary characteristics, but mostly the details are left for the player's mind to fill in. Dan Schmidt's For a Change did something similar (though to a much greater extent, of course, since the level of abstraction there was much higher), and in many ways it's a liberating experience to be encouraged to fill in relevant sensory details for yourself. Paralleling this are the verbs that you use to interact with other characters and with the environment, verbs which either aren't standard-IF at all or are used in highly unusual ways; the player is forced to put together his or her own images of how those verbs work.
The plot, for its own part, has its own logic, which, like everything else, may not be initially apparent; themes that seem quite sensible after they're encountered a few times may simply be baffling the first time or two they appear. There's an adaptive hint system that fills in most of the gaps (though not all), and while Worlds Apart is far from puzzle-oriented, it's likely that most players will end up using the hints at least once or twice. It's not so much that the puzzles are hard as that they require being on the author's wavelength. One that initially stumped me involved applying recently learned knowledge, and while I recognized immediately what to do, I didn't manage to supply the proper verb for quite a while. (It wasn't a verb that I, or anyone else, had ever encountered before, and while the game gave me an obvious clue, I tried to convey the action through more conventional verbs.) This isn't, I hasten to add, a bad thing. The world of Worlds Apart is all the more immersive for its strangeness. But it's not impossible that some might find it frustrating.
One of the greatest strengths of Worlds Apart is its cast of characters. True, you don't interact with them in especially complex ways; many of the interactions amount to cut-scenes, and much of the rest of it is ASK/TELL--but these are impressively complex characters. There isn't a thoroughgoing hero or villain among them; all have their faults and virtues, and while some are more likeable than others, none are there merely to be loved or loathed. Better still, their various personalities aren't merely identifying features ("here comes X, and he's going to display his character trait so that we don't confuse him with Y")--the plot depends on those personalities, and understanding the characters mean understanding why the plot unfolds the way it does. They also have some fairly complex relationships with each other, and much of what you learn about them you pick up secondhand, adding to the complexity. Better still, there's one character whose motivations and true nature are almost entirely open to interpretation (or so it seemed to me), and how the player chooses to perceive that character's actions may, or may not, shape how he or she views the rest of the story. There's no special technical wizardry that I could discern behind the character development--just good writing and lots and lots of ASK/TELL topics--but they come alive, arguably more so than in any work of IF in memory. And if some remain a bit opaque at the end of the story, well, it adds to the aura of mystery.
The writing is uniformly excellent: it's full of details, as noted, but generally the descriptions aren't so long that they become ponderous. Typical of this economical approach is this passage:
You have come to a secluded glade, half-sheltered from the elements by the many trees extending their branches out over the clearing. One of these in particular catches your eye, a gentle giant of a ch'nuka whose boughs stretch wide in every direction. Once, it might have shaded this place on its own, but now it shows signs of failing health--some of the branches are almost bare, and decaying leaves surround the trunk in piles and litter the clearing, although it feels like summer, and the other vegetation here is thriving.All the details necessary to set the scene are here--tree, leaves, vegetation--but the author also manages to convey the feel of the setting, and the tree that dominates the glade also dominates your impression of the place. The decay of the ch'nuka is more important than the continued vitality of the surrounding vegetation, and so it dominates the description; had the author chosen to give the other vegetation more attention, the extent to which this particular tree affects your perception of the scene would be lost. Moreover, the contrast between the dying tree and the thriving vegetation wouldn't work as well if it were explicitly pointed out; leaving the reader to draw the contrast and wonder about it works much better. Here, and elsewhere, the author eschews a camcorder approach for a more subjective, intuitive account--the aspect of the scene that draws your attention not only is described in more detail, but also colors your overall view of the setting. The author's writing skills are particularly apparent late in the game, when there's a Wishbringeresque transformation of your surroundings; not only are the changed features of the landscape vividly rendered, but every scene is emotionally charged in ways similar to the above.
Worlds Apart is not a flawless effort (as opposed, of course, to all those flawless works of IF out there). There are some questionable game design choices--at one point, for instance, you happen across a book with a great deal of information that becomes pertinent to a certain task, or series of tasks. Unfortunately, you can't take the book with you when you're carrying out the tasks (logically, given the nature of the assignment), and you may end up having to retrace your steps to consult the book that you couldn't take with you. The worldbuilding that the inclusion of the book accomplishes is outstanding--thorough and plausible--but the frustration aspect threatens to yank the player out of an otherwise immersive scene. The progress of the story sometimes depends too much on wandering around and eventually noticing that something has changed in an unforeseeable way, and while that encourages frequent re-exploration, it may prove frustrating to the player who wants the story to keep moving. The hint system fills in the gaps most of the time, but there are a few gaps. And the end is a bit abrupt; there's a reference to a possible sequel, but it's disappointing to leave the game's world with so much unresolved.
There is much to like about Worlds Apart, in the end--in quantity and quality, the detail that went into the worldbuilding is unmatched in any work of IF in recent memory, and it's unlikely that any player will catch all, or even most, of the story on the first try. If it's a little inaccessible at first, that comes with the territory--i.e., introducing the player into a highly complex and well-developed world--and it's hardly a fatal flaw. In its interactivity and in the quality of its storytelling, Worlds Apart is a remarkable accomplishment.