|Publishers|| JP Spike |
NA Aksys Games
|Release dates|| Nintendo DS |
JP December 10, 2009
NA November 16, 2010
JP May 29, 2013
WW March 17, 2014
|Platforms|| Nintendo DS|
Zero Escape: Nine Hours, Nine Persons, Nine Doors, also simply known as 999, is an adventure game for the Nintendo DS and the first entry of the Zero Escape series developed by Chunsoft and published in Japan by Spike on December 10, 2009, and in North America by Aksys Games on November 16, 2010.
The game's genre is a mix of psychological horror, mystery, suspense, thriller, and science fiction, with slight elements of humor and comedy to fill in the gaps when the atmosphere isn't so dark. The gameplay is a mix of visual novel, escape-the-room and puzzle.
On May 29, 2013, the game was ported to iOS and released in Japan. The port was named 9 Hours 9 People 9 Doors HD Smart Sound Novel, as it was released as part of the Smart Sound Novel series. The escape room puzzles were removed in favor of more focus on the visual novel aspects. The English version, titled Zero Escape: 9 Hours, 9 Persons, 9 Doors: The Novel, or simply 999: The Novel, was released on March 17, 2014 worldwide.
The story follows Junpei who is abducted and placed aboard an empty, sinking cruise liner along with eight other people. The cruise liner resembles the RMS Titanic, a ship which killed over 1500 in the early 20th century. The nine people are forced to participate in the "Nonary Game", a deadly game which involves numerical bracelets, small bombs in each player's stomach that will detonate and kill them if they disobey, exploring the ship and solving escape-the-room puzzles in order to survive and escape before they drown in 9 hours. The players also attempt to find out why they were kidnapped.
- Note: This plot summary only contains the events of the Safe and the True ending because the other endings aren't necessary for the True ending. For the other endings, see here.
- "The water is rising, there are 9 doors and time is running out... Seek a door that carries a 9. 9 hours. That is the time you will be given to make your escape. Now, it is time. Let our game begin."
On November 1st, 2027, Junpei, a normal college student, awakens inside of a small locked room; his last memory is that of being incapacitated using an inhalational anaesthetic and then abducted by an unknown person in a gas mask around midnight. Junpei infers that he is aboard a ship based on his surroundings and discovers that a metallic bracelet with the number 5 on the electronic display has been affixed to his wrist. Junpei is forced to escape the room by means of solving puzzles within it before the room floods from a leaking window.
Junpei escapes to the upper decks and encounters eight other people, who are also fixed with their own bracelets with unique digits. Junpei identifies one of them as his childhood friend Akane Kurashiki. As they find that the ship is no longer taking on water, they are greeted by their unseen host over a loudspeaker. The host, Zero, informs them they are playing the Nonary Game, which they can only escape by finding a door marked with a 9 within nine hours; fail and the ship will sink and everyone on-board will drown. They learn of electronic devices called REDs and DEADs near each marked numbered door that assure that only three to five people whose bracelet numbers' total digital root equals the number on the door can pass through each door; otherwise, a small bomb planted in each person's stomach will be detonated, killing them. Each player has a number marked from 1 to 9.
As the group assign themselves code names (with the exception of Junpei whose name was accidentally revealed to the group by Akane earlier), they begin to plan their escape, as the 9th Man holds Clover hostage and forces Ace and Clover to help him through a numbered door (Door 5). 9 + 1 + 4 = 14 = 1 + 4 = 5. When the 9th Man ventures alone through it, he is killed when the bomb in his stomach detonates. The group opens the door to see his bloody corpse, scattered pieces of flesh, and organs strewn across the floor.
Realizing that the game is real and anyone can die at any moment, the group proceeds to explore the ship, splitting into groups as necessary. The player has the option to select which group to travel with (Door 4 or 5) and other decisions that ultimately affect the fate of the game.
Door 4 or 5?
Depending on the choices made, Junpei learns of several strange stories that involve forms of morphic resonance communication between people and entities from those groups he travels with, as well as stories of a woman named All-ice, an Egyptian priestess apparently frozen in ice-9 for centuries.
If Junpei chooses Door 4, he explores the 2nd class cabin and kitchen with Santa, June and Lotus.
If Junpei chooses Door 5, he explores the 1st class cabin and casino with Snake and Seven.
No matter what happens, the group reaches the Large hospital room which has three more doors: 3, 7 and 8. Unfortunately, one player who is blind, whose codename is Snake, goes missing. After conducting a search and being unable to locate him, they decided that they had to move on through the next set of doors before time runs out. Lotus explained that the only way to allow the most players to proceed was to sacrifice someone and leave them behind. June opposed the idea but to allow the others to proceed, Ace volunteered to stay behind. He injected himself with an aesthetic called Soporil, knocking himself out, so that the other players could not take him with them.
Door 3, 7 or 8?
Junpei chooses Door 3, 7 or 8.
If Door 3, Junpei teams up with June, Santa and Seven and they enter the shower room.
If Door 7, Junpei teams up with Clover and Seven and they enter the operating room.
If Door 8, Junpei teams up with Lotus and Clover and they enter the laboratory.
The other players finally escaped from their rooms and surprisingly met back in the hospital room.
Snake's corpse is found in the shower room behind Door 3, and Clover, Snake's younger sister, becomes distraught, suspecting that some of the other players must have forced Snake behind Door 3.
Doors 1, 2 or 6?
The next "set" of doors is 1, 2 and 6, which are scattered throughout the ship. The group holds a vote using a paper pile, but Junpei rigs it so that he votes last and is able to go through Door 1, 2 or 6 at his own volition.
The player is required to experience the "Safe" ending in order to access the "True" ending which will otherwise end prematurely with a "To Be Continued" message via the Coffin ending. In order to get the safe ending, the player must go through Door 5, then 8, then 6.
In the cargo room, Junpei soon discovers from Santa that Ace owns a company called Cradle Pharmaceutical and thought that he may be suffering from prosopagnosia. After discovering the chapel and finding the two Door 9s, the group met up with Lotus and Seven near the central staircase. They told them that Clover was missing and the players split up to go try to find her. Junpei took June with him and the two searched the large hospital and the shower room. In the shower room, Junpei realizes that the body there is not Snake's since it has a bone from its left arm, and he remembers Clover telling him in the laboratory that Snake's was prosthetic.
It turns out that Clover was murdered by an unknown assailant, possibly the same murderer as her brother Snake. Clover's body is discovered inside the first class bathroom with a safe, which Junpei had passed through earlier on. After a cryptic note found in Clover's hand allows Junpei to figure out the combination to the safe, he opens the safe, inside which is information that sheds some light on Zero's true motives. Nine years ago, the First Nonary Game was held, and it is revealed that members of the current party were involved in it. Among these members is Zero's primary target; Gentarou Hongou, the CEO of Cradle Pharmaceutical.
After concluding that the Zero had in fact set up a decoy to be murdered in Snake's place, and that Ace is a prosopagnosia patient, Junpei accuses Ace of murdering both the decoy and Clover, and claims that Ace is in fact Gentarou Hongou himself. During the second Nonary Game, Ace had lured the 9th Man to act as he did to test the seriousness of the game and to avoid his identity being revealed, as well as obtain the 9 bracelet he possessed. Ace also kills two other Cradle executives that Zero had planted for revenge for the first Nonary Game.
Ace eventually admits to the allegations, and holds Lotus up at gunpoint in order to escape. He also reveals that he orchestrated the 9th man's death in order to obtain the 9th bracelet and protect his true identity. Junpei, Seven, Santa and June pursue Ace, but Santa and June decide to stay behind when June starts feeling weak and feverish.
In the chapel, Junpei also discovers that Snake is alive, and was locked inside a coffin and dresses in mysterious cult-like robes. Junpei and Seven omit the details of Clover's death from Snake. Junpei, Seven and Snake exit the final 9th door and find themselves at the entrance to an incinerator, which Snake instructs them to open and enter.
Inside the incinerator they encounter Ace, who's still holding Lotus at gunpoint. Ace reveals to Snake that he killed Clover (something Junpei and Seven were unable to tell him), causing Snake to fly into a rage and attack Ace. However, even after using up all his revolver bullets, Ace is unable to successfully kill Snake. Snake pins him down, vowing to burn along with him when the incinerator activates. Seven and Lotus force a distraught Junpei out of the incinerator, while Ace and Snake get locked inside and burn to death.
Junpei decides to go back to retrieve June and Santa, and finds a very ill June inside the chapel. Zero then speaks up, telling Junpei that the game is over, and the loser has been decided. When Junpei insists that he hasn't lost yet, Zero reveals that he was referring to himself as the loser. Junpei notices a door close, and thinking he might find Zero, leaves June to check it out. He doesn't find anyone, and when he returns, June has disappeared. Shocked and anguished, he cries out for her before being knocked out by a Soporil gas grenade.
After receiving the Safe ending, the True ending can be unlocked. In order to get the True ending, the player must go through Door 4, accept a clover bookmark from Santa, listen to a conversation about ice in a freezer, go through Door 7, then Door 1.
Junpei decided to go with Ace and Clover through Door 1, leaving Santa, June, Seven, and Lotus to go through Door 6. Junpei and his group opened up the Earth door and go into Door 1, finding themselves in the Chart room. While sending Ace to investigate the other half of the room, he tried to start a private conversation with Clover, asking her to finish her story from the operating room. She refused, saying that she did not want to talk about it, but asked him about whom he suspected to have killed Snake. The only possible option had everyone except Junpei, June, and Clover working together. Junpei dismissed it as unlikely, and Clover agreed, suggesting Santa and Seven killed Snake. Clover started to elaborate, but Ace interrupted them. He told Junpei that he wanted to talk to him and the two left for the wheelhouse. He told Junpei that he knew about Junpei's "trick" to get the door he wanted by reaching into his pocket for the papers. Junpei later found the pocket watch needed to open the exit and the three of them continued on. Practically right outside the door was the Captain's quarters.
They found a corpse of a man wearing a captain's outfit, a bracelet on his wrist that had "0" on its face, and a bloody axe next to his body. He asked Clover if she also thought the dead man they nicknamed 'Cap' was Zero but she insisted that Zero was one of the players. Junpei also noticed that it would be too obvious if the dead man was Zero, as the clues in the room felt too contrived. He and Clover examined the body closely for more clues and mentioned that he had an easy death compared to Snake's, who had a bone sticking out of his left arm. Clover quickly changed her expression to a look of surprise. She asked if Junpei was sure if it was the left arm and he confirmed it.
Suddenly, she started crying and leapt in Junpei's arm, thanking him and told him that Snake was still alive somewhere. She also thanked him for the bookmark that he gave her, and he mentions that Santa gave it to him. Clover said that Santa must have been one of the subjects on the ship with her brother, because he knew the "leaf words". Clover decided to finish up her story about the experiment that happened on the ship. She revealed that the Nonary Game was played on the ship. Clover mentioned that a girl had died on the ship Snake was on. Clover was about to reveal her name, but Ace interrupted them again.
After escaping the room, the three rushed down the central staircase to meet up with the other players. An excited June told them that they had found Door 9 and, full of excitement, they rushed to the elevators. Door 9's location turned out to be the chapel and to Junpei's surprise, there were two sets of Door 9s. That meant everyone could escape but Clover calculated all of the possible combinations and concluded that if four people go, three stay behind, and if three go, four stay behind. Seven attempted to sacrifice himself so the other six can leave, but was met by harsh criticism from the other players. Santa spoke up and flatly stated that he was against leaving Seven alone. Santa quickly got out a golden revolver and held June hostage. He ordered Ace and Lotus to authenticate at the big Door 9. Santa forced them through the door and after nine seconds, it closed, leaving Junpei, Clover, and Seven alone in the chapel.
As the room became quiet, they heard a pounding noise. They quickly looked around the room for the source of the noise and soon found it was coming from the coffin. A keypad was on it but no clues on the password for it. While Junpei was thinking, a voice in his head told him the sinister hand tip. He pressed his buttons on his bracelet in the correct order and eight numbers blinked on the display (14383421). He typed in the numbers on the keypad and the lock on the coffin opens. To their surprise, Snake emerged out of the coffin. Clover leapt into Snake's arms and tearfully welcomed him back to the group.
After Clover calmed down, Junpei and Seven told him everything that had happened since he was gone. They asked him why his clothes had been replaced, but the only thing he remembered was being knocked out by soporific gas while looking for the RED parts. Snake mentioned that it was 4:30 already and that they had to get moving. They authenticated and the small Door 9 opened. Before they entered, Junpei quickly wanted to see what the value of the captain's bracelet was. After some testing, they found that the bracelet had a value of 6. Snake assumed that June's bracelet was flipped and that it was actually 9 and that Santa's bracelet worked as the 0 bracelet. Snake inferred that Santa was Zero and that he set the entire game up.
Running out of time, they proceed through the small door 9. Searching the hallway that led from the door, they found a door with a Neptune symbol on it. They didn't have the key to open it, so they looked around more, eventually finding a door with a Uranus card scanner next to it. Junpei opened the door and they found themselves in a huge library. Junpei remembered that ALL-ICE might be nearby and started his search. While they were searching for a way out, Junpei confronted Snake and asked him to tell him about the experiment that happened 9 years ago.
They move up to the top floor and Snake starts talking. He had been told to keep quiet of the events 9 years ago in the braille message Zero had given him. Snake was sure that even if Zero was Santa, he wouldn't kill them because he was in the same group as Snake. Snake told him that the experiment was organized by Cradle Pharmaceutical and the details of the experiment. Before they leave, Junpei asked if Snake was sure there had been 18 kids in the experiment since the news reported on 16. The two remaining kids had no relatives known but their names were Aoi and Akane, Akane being the girl that had died during the experiment. Shocked at Snake's answer, Junpei started to ponder whether the Akane Snake was talking about was the same person as June. Since Snake did not reveal her last name, so Junpei reassured himself that they were not the same person.
In the study, Junpei is told of the events leading up to this point. Nine years ago in November 2018, Cradle Pharmaceutical, led by CEO Gentarou Hongou, kidnapped nine sets of siblings (18 children in total) for an experiment involving morphic fields. Hongou's desire was to understand morphic fields to try to cure his prosopagnosia (facial blindness). People are more easily able to access morphic fields under conditions of "epiphany" and "danger" — thus, trying to solve problems in a life-and-death situation, exactly what the Nonary Game sets up.
The kidnapped children included Snake (true name Light) and Clover, and Santa (true name Aoi) and Akane, as well as Lotus' children, twins Nona and Ennea. One of each set of siblings was to be placed aboard the Gigantic in the Atlantic Ocean, the sister ship of the RMS Titanic, the others in Building Q, a secret facility in the Nevada desert, that both had identical interiors. Both sets of children were to play the Nonary Game with those in the building, solving the puzzles and telepathically sending the solutions to those aboard the ship. However, the experiment went awry: Akane was misplaced, put alongside her brother Santa/Aoi on the ship rather than sent to Building Q.
Seven, a detective at the time, had discovered Cradle to be behind the kidnappings, and was able to rescue the children in the incinerator on the ship using a makeshift rope made of bedsheets. As they fled, Hongou recaptured Akane and forced her back into the incinerator room to continue the experiment alone. She was unable to solve the Sudoku puzzle to escape the incinerator, and apparently died. However, Akane (June) has been playing the Nonary Game with Junpei and the rest of the group the whole time, implying a mysterious paradox.
Junpei, Clover, Seven and Snake catch up to June, Ace, Santa and Lotus in the incinerator. Akane notices Junpei and tells him not to worry about her. Sometime in the next few minutes, she sneaks out of the incinerator while Junpei and the rest of the group aren't looking. Ace holds Lotus hostage with Santa's revolver and forces her to authenticate. The door does not open, to Ace's dismay. He tries over and again, but the door still won't budge.
Seven then charges at Ace and floors him. Junpei, using his memory of a previous timeline, gets Ace to confess to the murder of the 3 other executives of Cradle Pharmaceutical and he is shocked to find that Snake is still alive. Junpei also reveals that Ace was being manipulated by Zero to purposely kill the other executives and that he concluded to have done did it so he could get revenge for the events of the First Nonary Game.
Since Junpei thinks Santa is Zero, he questions him and he admits that he is Akane's brother, but that he is not Zero, but merely an assistant to him. Santa says that this whole Nonary Game was set up so Junpei could save Akane from dying in the incinerator in the past.
The player learns that the gameplay they have witnessed has been through the viewpoint of young Akane during the first Nonary Game. She was able to connect to Junpei in the second Nonary Game nine years in the future through morphic fields and watch his actions. Akane was able to see multiple futures for Junpei depending on his choices (i.e. the multiple endings), and is able to provide him with guidance as to which choices will succeed.
Junpei and the group also learn that Zero is really Akane assisted by Santa/Aoi, having created the second Nonary Game to guide Junpei to the same puzzle in the incinerator that Akane faced nine years earlier. Santa/Aoi begins the incineration process. Junpei, under duress and linked by the same situation, is able to communicate back to young Akane, and demonstrates the solution to the puzzle to her. In addition, young Akane gives Junpei a string of additions: 2 + 4 + 5 + 7 + 8, which is the solution to open Door q. Back in the past, young Akane reunites with Seven, Aoi, Light, and the other children, and escapes the Gigantic ship with Seven in a rowboat before it sinks into the Atlantic Ocean.
In the present, Junpei and his friends escape, discovering they were not inside either the Titanic or Gigantic, but rather, Building Q in the Nevada Desert all along, and that their bracelets did not contain detonators (except for Kubota and Nijisaki). Outside, they find an SUV with Ace tied up in the trunk, and they drive off, hoping to catch up to Aoi and Akane. They encounter a female hitchhiker in Egyptian clothing, who Junpei recognizes to be Alice, and Clover stops the car to let her on.
- Main article: Nine Hours, Nine Persons, Nine Doors endings
- Coffin - Obtained if the player attempts to receive the True ending without obtaining the Safe ending.
- Submarine - Junpei finds a submarine in a storage room, but Ace kills everyone before they can escape.
- Knife - Junpei finds Lotus' corpse. Suddenly, Junpei is killed by Ace with a knife to the back.
- Axe - Clover, distraught by Light's supposed death, secretly kills Santa and Seven in revenge. She also kills June because she got in the way. Later, she throws their bracelets (3, 7 and 6) on the floor and tells Junpei they can escape with them. To Junpei's horror, he remembers the bracelets are removed if a player dies. Clover offers Junpei the opportunity to escape with her (4+5+0=9), but she kills him with an axe.
- Syringe (iOS version only) - Clover kills Junpei with a syringe and leaves him to drown.
|A tall, grave older man with a streak of gray in his hair, he is often the voice of calm reason when events descend into chaos. His bracelet number is 1, hence the name Ace.|
|A young man with a princely demeanor, he is an unending source of information, but tends to only reveal it when there is no other option. His bracelet number is 2, from the term "snake eyes". Ironically, Snake is blind but that does not stop him from being able to work as well as another normal person.|
|Little more than a punk with silver hair and a bad attitude at first glance, this clever guy keeps pushing forward and doesn't like dealing with indecisiveness. His bracelet number is 3 so his name comes from "san", the Japanese word for "three" and that he references Santa Claus several times.|
|Prone to rapid swings of emotion, this pink haired girl doesn't hesitate to speak her mind or put people in their place. Her bracelet number is 4 so her codename comes from the four-leaf clover, which is a symbol of good luck. She is the sister of Snake and so does everything to try to stay with him, unless he goes against her intentions.|
|The main protagonist of the game. After he wakes up to find he's been transported to a strange location, he takes it upon himself to figure out all the cryptic clues and ensure the survival of everyone trapped with him. His bracelet number is 5 and is the only one not to choose his own codename due to June accidentally mentioning his name.|
|The childhood friend of Junpei. Akane Kurashiki is her actual name, although she chooses the codename June once she accidentally reveals Junpei's name. She is a delicate girl who wants no one to be left behind during the Nonary Game. Her bracelet number is 6, from the month June.|
|A large, bumbling mountain of a man, his appearance and behavior hide an intelligent mind well-equipped for solving problems. His size gives him the strength to do certain functions that only he or Ace are able to do. His bracelet number is 7 and obviously, his codename is his bracelet number.|
|A self-serving, barely-dressed woman with unknown skills and knowledge, she does whatever she can to find her way out. Her bracelet number is 8 and Lotus comes from the flower itself, which has 8 petals.|
|A fidgety, nervous man from the start, he knows more than he's letting on. The 9th Man is the only one who does not get to pick what his codename is so the rest of the players refer to him as the 9th Man during the Nonary Game.|
|The mastermind behind the Nonary Game. Their identity is a mystery and what their motives are for putting the 9 players in the Nonary Game are unknown.|
The gameplay is divided into two parts:
- The puzzle part is when the player must solve the puzzles that are blocking their way in order to progress through the game. There are 16 escape rooms in total. The game also contains a calculator with a digital root function to aid in escape rooms.
- The visual novel part in which the player can talk to the other characters and make decisions that affect the story of the game. Junpei or the other characters may die depending on what doors and dialogue choices the player makes.
There are 6 endings in total (one exclusive to the iOS version). The player's decisions affect which ending is received. Only one ending is the true ending.
Unfortunately, the player must re-solve the puzzle rooms to obtain all the endings in the DS version. This was fixed in the iOS version and in Virtue's Last Reward.
In the iOS version, the escape room puzzles were removed in favor of narration of the events that happened in the room. The story is now presented in a comic book style and a flow chart that allows the player to skip to different parts of the plot. Because of the bottom screen being removed, the narration appears in the same screen as the dialogue. While in an escape room, only the cutscenes are seen in each room.
Although in-game the ship will sink in 9 hours, there isn't a single time limit in the entire game so the player can play the game and solve all of its puzzles at their own pace.
The soundtrack for the game was composed by Shinji Hosoe. Some of these songs are also used in Virtue's Last Reward.
The iOS version of the game features higher-quality music compared to the compressed DS version. A fan-rip of the iOS music can be found here.
- 9 hours, 9 persons, 9 doors - Plays in intro.
- Unary Game - Plays in 3rd class cabin. Also plays during scenes, especially when the players are in a hurry.
- Extreme Extrication - Plays during scenes.
- Binary Game - Plays in 2nd class cabin and 1st class cabin.
- Riddle and Puzzle - Plays during scenes, especially during scientific discussions.
- Ternary Game - Plays in Kitchen and Casino.
- Foreboding - Plays during scenes.
- Quaternary Game - Plays in Laboratory.
- Recollection - Plays when Akane tells Junpei about the dead rabbits, during the Submarine ending, during the Safe ending, when Clover hugs Junpei and Snake, and during the True ending when Akane is saved and reunited with Aoi in the past.
- Quinary Game - Plays in chart room, confinement room, and steam engine room.
- Trepidation - Plays during scenes, especially horrifying ones.
- Senary Game - Plays in Captain's Quarters, Torture room and Cargo room.
- Quietus - Plays when Junpei dies and at the end of the Safe Ending.
- Imaginary - Plays during scenes.
- Septenary Game - Plays in Operating room and Shower room.
- Tranquility - Plays moments before the Knife ending completes.
- Tinderbox - Plays during scenes.
- Eternitybox - Plays during scenes.
- Who is Zero? - Plays during scenes.
- Octal Game - Plays in Library.
- Nonary Game- Plays in Study.
- Chill and Rigor - Plays during scenes, especially after a death.
- Digital Root - Plays during scenes, especially after a revelation.
- Morphogenetic Sorrow - Plays during Sudoku and in the incinerator during the Safe Ending.
- 9 years - Plays during the epilogue.
999 received generally favorable reviews from critics, with several near perfect scores emphasizing its well-written suspenseful story, presentation, characters, music, and escape-the-room gameplay. Critics have also praised its experimental hybridization of visual novel, puzzle and "choose your own adventure".
In the following years since its release, 999 and the Zero Escape series have gained a bit of a cult following in its fandom, primarily in the anime and video game fan community, and it has inspired a lot of fan material such as cosplay, music, fan-fiction, art, etc.
However, this isn't to say the game is perfect by any means. Many players were dissatisfied with the amount of repetitive tutorials in the beginning of the game, and having to re-do the same escape rooms in order to achieve another ending. For example, if the player wants to achieve all six endings, they must solve the 3rd class cabin six times. This was rectified in Virtue's Last Reward, which added a flow chart. In the DS version of the game, it is possible to fast forward text that is already read using the d-pad, however, there is no auto advancing text, so newcomers of the game should expect a lot of tapping, clicking and reading.
Adding onto its criticism, it is also notable that for the majority of the game, it is portrayed as a realistic murder detective mystery, and then at the end of the game, paranormal and supernatural ideas are introduced such as time paradoxes, morphogenetic fields, and communicating through time. These paranormal plot twists may be off-putting to some players and viewed as poor writing (depending on the opinions of the player), in the same vein as Indigo Prophecy. However, in defense of this aspect of the game, it can also be argued that these ideas are gradually introduced in conversations, such as Lotus explaining the morphogenetic field early in the game in the 2nd class cabin.
One final point of criticism is its pacing. The urgency portrayed in the game's story sometimes may seem at odds with the tone or timing of conversations, such having a lengthy scientific conversation about the properties of ice while three characters are trapped inside a freezer and are slowly freezing to death in order to receive the true ending.
Also criticized was the game's horror atmosphere: characters crack lighthearted jokes things such as foot fetishes and blue liquid being alien blood after dead bodies are found in the ship.
The iOS version was criticized for removing the escape rooms from the game, as well as the character animations, but it was praised for its higher-quality HD art.
It should be taken into account that the Zero Escape series has a mixture of humor which may not appeal to everyone, ranging across sexual innuendoes (of both heterosexual and homosexual variety) puns, wordplay, video game references and similar. There is also a lot of minor to moderate profanities throughout (fuck, crap, bitch, etc.)
Additionally, the game includes detailed descriptions of gore, murder and suicide which are often accompanied by anime art of dead bodies covered in blood - as per its 17+ age rating. Like all media, just because the game is drawn in a cartoonish or anime style, this does not mean it will be suitable for audiences of a sensitive disposition.
It should also be noted that the Zero Escape series is on Nintendo DS and 3DS, and Nintendo is often viewed by many parents as a "family and child friendly" company. Despite this, games like Zero Escape and its counterparts are not recommended for children or younger teenagers, as shown by its age rating; parents should consider these factors before they allow their child to play these games.
DS and iOS differences
However, most Zero Escape fans highly recommend playing the DS version over the iOS version first. The DS version also has an interesting mechanic near the end of the game which is completely non-existent in the iOS version, which is difficult to explain to someone unfamiliar with the Zero Escape series without spoiling it.
The DS version has low pixelated graphics (256 × 192) and compressed music quality, and no flow chart meaning the player must solve the first escape room six times if they want all six endings. It's also lacking the Syringe ending.
The iOS version has a flow chart, HD art, high quality music, but no character animations (just about 8 or 10 static portraits for each character), no voice beeps (the DS version has different tones of voice beeps to make it seem like the characters have voices, such as Clover having a high-voice pitch beep and Seven having a low-pitch voice beep), and no escape rooms.
A definitive version of the game would have all these aspects:
- HD art
- High-quality music
- Flow chart
- Syringe ending
- Character animations
- Voice beeps (or even full English/Japanese voice acting which can be disabled if the player doesn't want voice acting)
- Translations into other languages (999 is only available in English and Japanese, and there's no French, Spanish, German, etc translations)
- Fixed mistakes
It is unknown if 999 will receive a full remake or remaster some day.
- A free watch bracelet was included in pre-orders.
- 999 is also playable on 3DS via backwards compatibility, and also on a DS emulator. However, the final puzzle is upside down on an emulator so the player must change the rotation in the emulator's settings.
- Games on Nintendo DS that are similar to 999 include Time Hollow, The World Ends with You, Ghost Trick: Phantom Detective, Trace Memory / Another Code and Hotel Dusk: Room 215.
- The game's design team is led by Kotaro Uchikoshi, who was also the writer of the acclaimed visual novel Ever 17: The Out of Infinity.
- The 999 novelization has several plot differences including:
- Nona sharing the same fate as Akane.
- Light giving the rest of the children four-leaf-clover accessories instead of actual four-leaf-clovers.
- Light becoming blind by falling off of a cliff instead of in a car accident, while trying to help Clover.
- Akane having amnesia during the Second Nonary Game when she is June.
- Ace dying at the end of the novel in a similar fashion to the 9th man.
- Clover having one of the four leaf clover accessories from the first Nonary Game.
- The final puzzle of the game being a Rubik's Cube and is not located in the incinerator. 
- In the DS version, closing the DS and reopening it causes the sound of an engine starting up to play.
- According to Kotaro Uchikoshi, hands were originally going to be a very important part of the story, but the idea was declared unacceptable near the end of the production stage. This apparently forced Uchikoshi to rewrite the entire story. 
- According to Kotaro Uchikoshi, the characters were based off the nine character archetypes of the Enneagram of Personality, and also compared them to Star Wars characters.
- The game Muramusa Rebirth contains a reference to Nine Hours, Nine Persons, Nine Doors. One of its silver trophies is called "Hours, Persons, Doors", which is received when the player performs a 999-hit combo.
- Danganronpa: Trigger Happy Havoc contains a silver trophy called "Nine Coins, Nine Purses, Nine Bears", received for collecting 999 Monocoins.
- The bottom screen of the DS version represents young Akane seeing events through Junpei's eyes. This is revealed when Akane says, "Somehow I found myself in Junpei's mind, 9 years in the future. But I didn't lose myself... I was living in 2 realities at once. One was the present, and the other was the future. Perhaps you can think of it as 2 movies showing on the same screen, at the same time. Eventually, it becomes difficult to separate them, and determine which movie is which. However, if I concentrated, I was able to focus on one or the other."
- The game also has two unlockable previews, one after completing the coffin ending and another after completing the safe ending. Both serve as hints on how to get the safe and true endings.
- There is an unused room called the Reactor.
- In the True ending, every female player is held hostage. Clover is held at knifepoint by the 9th man. Akane gets held at gunpoint by Aoi. Lotus has a gun pointed at her head by Ace.
- DS website
- DS website (Japanese)
- Novel site
- Novel site (Japanese)
- 999: The Novel on iOS
- 999: The Novel (iPad) on iOS