999: Nine Hours, Nine Persons, Nine Doors

• If you want to remain unspoiled, DO NOT LOOK UP ANYTHING RELATED TO THE GAME, no matter how harmless it may sound. No art, no music, nothing. This may sound obvious, but bears mentioning because of how easy it is to spoil crucial plot elements via "related results" and such. This applies even if you've beaten the game, unless you want to learn important plot twists of both sequels.

• There's a Nintendo DS version of this game, and a 2017 remake. The remake is bundled with a remake of the sequel (VLR). The remade sequel is generally considered the best version, but the best version of the original is the DS one. That said, the remake might be worth a play-through for the voiced dialogues.

• For the original (Nintendo DS) version only:
  • The game features an excellent text skip option (by hold the stylus IIRC) enabled after the first time you reach an ending that will stop on any piece of text you haven't read. Learn to use it and love it, it'll save you lots of time.

• For the remake (PC) only:
  • The text skip option in the remake does NOT stop on text you haven't seen, so only use it when you're positive there's no incoming dialogue changes (usually you should skip segments using the flowchart instead).
  • Switch to the Novel Mode ASAP and forget the Adventure Mode exists, it's terrible and will show you less than half of the game text. The game will sometimes still try to switch to Adventure Mode, switch back manually when it does. Remember that you can look up the missed text with D-Pad/cursor up.
  • The calculator is worthless, you'll never have access to it when you have to calculate digital root.
  • In the flow menu (down arrow on keyboard or check your button layout) you can skip to the chapter, puzzle or decision you want to replay / change without going through the whole story.
  • The flow menu will highlight the "current" path the game considers you're on with a blue line, including past choices.
  • If you're attempting to finish the game without a guide and see all the endings, the flow menu has some key / lock icons that are colour-coded to give you hints on where the choices/events/actions/puzzles of interest are.

• Discussions and wiki articles about this game tend to spoil major plot points in future games. Even though this is a standalone game it's probably best to avoid looking it up, even if you've finished it, if you want to play future games.

• There are multiple (six) endings. After finishing the game for the first time, you can replay it and optionally skip all the dialog from previous play-throughs. There's a spoiler free guide to all of the endings here.

• In the puzzles, sometimes you have to click multiple times on the same object/surface to get different or definitive answers.

• You can save the game at any moment, even in the middle of a dialog.

• It's not really a puzzle game, it's a visual novel. The puzzles these games have are relatively easy & serve more as a "break" in the story than as the core of the game. That said, some puzzles are unintuitive. Some use non-decimal number bases, and it's not always easy to tell when an object is interactive.

• In the "flow" menu in the remake (down arrow on keyboard, check your button layout) you can skip to the chapter, puzzle or decision you want to replay / change without going through the whole story.

• The 2017 remake has a flow menu, which will highlight the "current" path the game considers you're on with a blue line, including past choices. It'll also let you skip to the chapter, puzzle, or decision you want to replay/change without going through the whole story.

• If you're attempting to finish the game without a guide & see all the endings, the flow menu has some key & lock icons that are colour-coded to give you hints on where the choices/events/actions/puzzles of interest are.