WARNING. This entry contains spoilers for several story aspects of Virtue's Last Reward and, by extension, 999. You have been warned.
999: Nine Hours, Nine Persons Nine Doors is a visual novel with escape-room sections for the Nintendo DS about nine people locked away in an enclosed environment and forced to play a bizarre game of puzzles in order to escaped.
It has been praised for crafty design and intriguing story, with branching paths that offer multiple endings, each revealing a bit of the overall mystery. After getting to an ending, you immediately want to start again to follow a different storyline and find out more.
It had two key problems with that mechanic:
Virtue's Last Reward is a visual novel with escape-room sections for the Nintendo 3DS, a sequel to 999 and a perfect solution those problems.
The story branches at several points, but at any moment the player desires, she's free to jump to any point in the story she's already been in, free to explore alternative branches whenever it suits her.
As for the escape-rooms, solving the puzzles provides a code, that allows you to proceed. If you ever need the code, it's stored for repeated use in the archive that the game provides.
And both of these have been made to be a gameplay necessity, rather than simply a convenience for the player. The story's branches close off, because proceeding would require information, that the player can only get obtain in a completely different branch, forcing her to jump around and look for clues, to unlock the paths to the endings.
To some this mechanic does not make sense - the player character isn't the player, and doesn't know what the player knows. It's the player who jumps around the storyline, not the character, right?
Wrong. The game starts making self-references, with characters commenting on things that happened in other story branches, even basing their decisions on some of their knowledge of alternative timelines, and the theory of quantum multiverses, along with Schrödinger's cat are set as a scientific basis for the timeline jumping that the main character performs.
And while all the endings are equally canon, equally valid, due this principle there is one ending, that could be easily called the "true" ending, because accessing it requires the player to have knowledge from every single other ending, and because it provides exposition on the finer points of the plot that the player might have missed or ignored, revealing final twissts one after another.
And the most beautiful thing is, that though Virtue's Last Reward consists mostly of reading and listening, twenty to thirty hours of it, roughly speaking, it is a perfect example of a story that would not work in any other medium.
Even though every single piece of plot is scripted and always plays out the same, the player is allowed to pick his own pace and path, experiencing the story in whatever order she pleases.
Had this been any other medium, like a book, or a tv series, all the events would have been played out in the same order, robbing the player of the joy of discovering that the protagonist is actually jumping through the story with her.
Ultimately, VLR is all about correcting mistakes - the entire premise is because the mastermind behind the events of the game wants to right a grave wrong, while the protagonist uses his ability to jump through timelines to correct mistakes of his own, repeatedly finding that he isn't the only person who changes his mind in alternate universes. I could not think of a better way to apply story to a mechanic that fixed the game's predecessor's main flaws.