999: Nine Hours, Nine Persons, Nine Doors

999: Nine Hours, Nine Persons, Nine Doors is a Japanese visual novel and adventure video game developed by Chunsoft. It is the first installment in the Zero Escape series, and was released in Japan in December 2009 and in North America in November 2010 for the Nintendo DS. The story follows Junpei, a college student who is abducted along with eight other people and forced to play the "Nonary Game", which puts its participants in a life-or-death situation, to escape from a sinking cruise liner. The gameplay alternates between two types of sections: Escape sections, where the player completes puzzles in escape-the-room scenarios; and Novel sections, where the player reads the game's narrative and makes decisions that influence the story toward one of six different endings.

Development of the game began after Kotaro Uchikoshi joined Chunsoft to write a visual novel for them that could reach a wider audience; Uchikoshi suggested adding puzzle elements that are integrated with the game's story. The inspiration for the story was the question of where inspiration comes from; while researching it, Uchikoshi came across Rupert Sheldrake's morphic resonance hypothesis, which became the main focus of the game's science fiction elements. The music was composed by Shinji Hosoe, while the characters were designed by Kinu Nishimura. The localization was handled by Aksys Games; they worked by the philosophy of keeping true to the spirit of the original Japanese version, aiming for natural-sounding English rather than following the original's exact wording.

999 was positively received, with reviewers praising the story, writing and puzzles, but criticizing the game's tone and trial-and-error gameplay. While the Japanese release was a commercial failure, the game sold better than expected for the genre in the United States. Although 999 was developed as a stand-alone title, its unexpected critical success in North America prompted the continuation of the series.