999 Nine Hours, Nine Persons, Nine Doors has two gameplay modes. The first is “Story Mode,” where the player reads the story and makes decisions which affect its progression. The other mode is “Escape Mode,” where you and your fellow abductees are trapped in a room, and you must explore it and solve puzzles to escape. See the controls page for more information on these two modes.
The game has six endings, only one of which is the “True” ending. The ending you get is based on the decisions you make throughout the game, mainly which of the numbered doors to go through. Only one of the 16 possible paths will lead to the “True” ending, and in fact you need to have seen one of the bad endings before you can see the good one. For more information, see the endings section in the appendix.
It is also important to remember that, even though the characters are acting under a nine hour time limit, you are not (except for one puzzle in the final room). So, take your time if you need it. There’s no rush.