Same principle as Myst: the game takes place in first person with a hand cursor on the screen to handle movement and interactions with the environment. The cursor will also sometimes change shape to indicate a specific action you can perform. The environment consists of a series of images, which you navigate by clicking where you would like to go. Say you want to enter a room: clicking on its doorway on your current image will bring up a different frame closer to the door, etc. The game is more detailed than its predecessor though, so there are more frames and more varied perspectives. Myst had a few frames which allowed you to look up or down, and Riven has a good deal more. The “zip” mode, which allows shortcuts to places you’ve already visited and appears as a lightning bolt cursor instead of the usual hand, still exists, but it still has the same drawbacks as in the previous game: it may make you miss out on some clues or screens where you need to manipulate something. It’s still possible to save at any time by bringing up a drop-down menu from the top of the screen.
Journals are still your main source of information about background events, and both Gehn and Catherine as just as happy to oblige as Atrus was in Myst. He only contributes one journal this time around, as does Catherine, while Gehn has two. Riven also introduces two journal-related novelties. Two of the puzzles you will encounter require codes to operate. These codes can be found in journals, and they are randomised in each playthrough, meaning that you can’t simply hightail it to the puzzle in question and short-circuit the entire game (which was a problem in Myst). I find that it’s a laudable evolution which serves to maintain the sense of immersion with each subsequent playthrough: you’re always in a situation where you don’t know the codes before you actually discover them in-game. There’s another puzzle which is solved by a randomised code, but that one isn’t written in a journal.
The second journal-related novelty is the introduction of a rudimentary inventory system. In Myst, all journals were confined to the Myst library, and any pages you picked up were simply registered by the cursor. In Riven, you’ll be carrying Atrus’ and Catherine’s journals with you, as well as the prison book, as they’re needed for storyline purposes. You can therefore access them whenever you like (just don’t use the prison book by accident…) by moving the cursor outside the frame: they’ll be located right below it.
As has already been mentioned, Riven has a rather different structure than the other games in the series (it even has its own linking sound, which is slightly different from its peers). Where Myst island functioned as a hub to which you returned upon exploring each of its connected ages in any order you chose, Riven is more linear. You mostly travel between islands in a set pattern (although there is a possible choice once you reach Crater Island), and, rather than being neatly confined to one island each, the puzzles are now interconnected. Meaning, for instance, that the first time you leave Temple Island, you will not have finished solving its main puzzle, as you’ll be missing some necessary information. This makes sense, since Riven, is, after all, one age, and it creates a welcome feeling of cohesion. It also ensures a steady level of attention, because, on top of the fact that the puzzles are decidedly more complex this time around, you never know when or where a potential clue could pop up. Myst had that, to a much lesser extent, with the torn note halves in Stoneship and Channelwood, as well as the directional noises in Mechanical and Selenitic, but it’s much better implemented in Riven. Of course, this has led to criticism of excessive difficulty and subtlety, but I genuinely enjoyed the challenge. As for the most likely candidates for the title of Most Difficult Puzzle, I’d name the Fire Marble puzzle (which is also the most extensive in the game) or the Moiety puzzle.
The game is less uncertain in the choices it offers than its predecessor. It’s pretty clear from the get-go that Gehn is up to no good, and, in that sense, your final goal is rather obvious. Still, at least one of the game’s choices requires a pretty big leap of faith (well…to be entirely exact, there are two leaps of faith, but the second one is scripted), and it’s not difficult to mess things up rather dramatically, even though you have to be deliberate about it. There are a whopping 10 different endings (although some are just variations on one theme), including one that can be achieved either by pure luck or by cheating, and while only one of these endings is good, as usual, there are now several lethal outcomes. The good ending has also received proper attention and is now both exciting and gratifying, unlike the one in Myst.