Nonlinear gameplay

When a level is sufficiently large and open-ended, it may be described as an open world,[4] or "sandbox game", though this term is often used incorrectly.[5][6] Open-world game designs have existed in some form since the 1980s, such as the space trading game Elite, and often make use of procedurally generated environments.

In a game with a sandbox mode, a player may turn off or ignore game objectives, or have unlimited access to items.[7] This can open up possibilities that were not intended by the game designer. A sandbox mode is an option in otherwise goal-oriented games and is distinguished from open-ended games that have no objectives, such as SimCity,[7] and Garry's Mod.[8]

Branching storylines are a common trend in visual novels, a subgenre of interactive narrative and adventure games. Visual novels frequently use multiple branching storylines to achieve multiple different endings, allowing non-linear freedom of choice along the way. Decision points within a visual novel often present players with the option of altering the course of events during the game, leading to many different possible outcomes.[12][13] Visual novels are popular in East Asia, especially in Japan where they account for nearly 70% of personal computer games released there.[14] A recent acclaimed example is 999: Nine Hours, Nine Persons, Nine Doors, where nearly every action and dialogue choice can lead to entirely new branching paths and endings. Each path only reveals certain aspects of the overall storyline and it is only after uncovering all the possible different paths and outcomes through multiple playthroughs that everything comes together to form a coherent well-written story.[15]

It is not uncommon for visual novels to have morality systems. A well-known example is the 2005 title School Days, an animated visual novel that Kotaku describes as going well beyond the usual "black and white choice systems" (referring to video games such as Mass Effect, Fallout 3 and BioShock) where the players "pick a side and stick with it" while leaving "the expansive middle area between unexplored". School Days instead encourages players to explore the grey, neutral middle-ground in order to view more interesting, "bad" endings.[16]

It is also not uncommon for visual novels to have multiple protagonists giving different perspectives on the story. C's Ware's EVE Burst Error (1995) introduced a unique twist to the system by allowing the player to switch between both protagonists at any time during the game, instead of finishing one protagonist's scenario before playing the other. EVE Burst Error often requires the player to have both protagonists co-operate with each other at various points during the game, with choices in one scenario affecting the other.[17] Fate/stay night is another example that features multiple perspectives.[18] Chunsoft sound novels such as Machi (1998) and 428: Shibuya Scramble (2008) develop this concept further, by allowing the player to alternate between the perspectives of several or more different characters, making choices with one character that have consequences for other characters.[19][20] 428 in particular features up to 85 different possible endings.[20]

Another approach to non-linear storytelling can be seen in Cosmology of Kyoto. The game lacks an overall plot, but it instead presents fragmented narratives and situations in a non-linear manner, as the player character encounters various non-player characters while wandering the city. These narratives are cross-referenced to an encyclopedia, providing background information as the narratives progress and as the player comes across various characters and locations, with various stories, situations and related information appearing at distinct locations.[21] It provides enough freedom to allow for the player to experiment with the game, such as using it as a resource for their own role-playing game campaign, for example.[22]

Branching storylines are also often used in role-playing video games (RPGs) to an extent. An early example, published in 1999, is the fantasy role-playing game Might and Magic VII: For Blood and Honor, where players have to choose between Light and Dark. While the dark side wants to destroy the world of Enroth, the light side tries to save it. The choice determines which grandmaster levels the player characters can obtain and the quests they have to do in that part of the game. Earlier in the game, the player already has to choose sides in a border conflict between Elves and Humans, or remain neutral. This affects the flag in their Castle Harmondale and a few quests, but not the outcome.

A second example is Obsidian Entertainment's Fallout: New Vegas, where the player's decisions influence whether one of three different factions gain control of the area surrounding post-apocalyptic Las Vegas. These factions include Caesar's Legion, a group of Roman-esque slavers; the New California Republic (NCR), an expansionist military government; and Mr. House, the enigmatic de facto ruler of New Vegas, in command of an army of robots that patrols the city. Each of the three sides aim to control Hoover Dam, which is still operational and supplying the American Southwest with power and clean, non-irradiated water; thus, control of the dam means effective control of the region. A fourth option, siding with a robot named Yes Man and prevailing upon or eliminating the other faction leaders, enables the player to go solo and take over the Hoover Dam for themselves.

Another RPG example is tri-Ace's Star Ocean series, where the storyline is not affected by moral alignments like in other role-playing games but, inspired by dating sims, by friendship and relationship points between each of the characters.[23] Star Ocean: The Second Story in particular offers as many as 86 different endings[24] with hundreds of permutations, setting a benchmark for the number of possible outcomes of a video game.[23] Another unique variation of this system is the Sakura Wars series, which features a real-time branching choice system where, during an event or conversation, the player must choose an action or dialogue choice within a time limit, or not to respond at all within that time; the player's choice, or lack thereof, affects the player character's relationship with other characters and in turn the direction and outcome of the storyline. Later games in the series added several variations, including an action gauge that can be raised up or down depending on the situation, and a gauge that the player can manipulate using the analog stick depending on the situation.[25] A similar type of conversation system later appeared in a more recent action role-playing game also published by Sega, Alpha Protocol.[26]

Another unique take on the concept is combining non-linear branching storytelling with the concepts of time travel and parallel universes. Early attempts at such an approach included Squaresoft's Chrono role-playing game series (1995–1999)[27] and ELF's visual novel YU-NO: A girl who chants love at the bound of this world (1996).[28] Radiant Historia takes it further by giving players the freedom to travel backwards and forwards through a timeline to alter the course of history, with each of their choices and actions significantly affect the timeline. The player can return to certain points in history and live through certain events again to make different choices and see different possible outcomes on the timeline.[27][29] The player can also travel back and forth between two parallel timelines,[30][31] and can obtain many possible parallel endings.[32] The PSP version of Tactics Ogre featured a "World" system that allows players to revisit key plot points and make different choices to see how the story unfolds differently.[33] Final Fantasy XIII-2 also features a similar non-linear time travel system to Radiant Historia.[34]