Between linear video game narratives and massively branching Gamebook affairs lies a "branch-and-bottleneck" story structure. In it, the game follows the same plot for all playthroughs early on, before giving the player a choice of where to take it next. This comes in two main variations:
- Exclusive Branches, a.k.a. Story Branching proper. The player chooses a subplot to follow, locking out all other options for the duration of the playthrough. However, at some point before the ending, every subplot leads back into a unified narrative, and the story is the same for all players again (unless the plot branches again, see below). A Choice-and-Consequence System is usually employed in this case to avoid devaluing the player's big choice by referencing it throughout the rest of the game.
- Complementary Branches, a.k.a. The Three Trials, are subplots that are usually localized geographically, with the player having to complete them all (unless a Fractional Winning Condition is involved) to progress to the linear finale. The player thus chooses the order in which to resolve these subplots, but all of their events will have occurred before the finale. Because Take Your Time is usually in effect in such games, all subplots are usually assumed to have taken place at roughly the same time; however, if the subplots actually take place at the same time and feature different character casts, they fall under the specific subtrope, Arbitrarily Serialized Simultaneous Adventures.
While the structure described above is the basic model, games can also have multiple branching-outs and bottlenecks per playthrough, including recursively nested ones of varying lengths and types. The first variation is a subtrope of Story Branching, the second is a type of Gotta Catch Them All. On a more meta level, an Omega Ending can be seen as a subtype of complementary branches, because you need to clear all other endings in any order to get it.
- Arbitrarily Serialized Simultaneous Adventures: Complementary branches that take place at the same in-universe time and focus on different playable characters.
- Multiple Game Openings: Exclusive branches that split up before the core gameplay even starts, then are bottlenecked backinto a unified plot.
- The Three Trials: If the player can complete said trials in any order to advance the plot, rather than having to do them in an explicitly or implicitly fixed sequence, they become complementary branches.
- Outcast gives you the mission of collecting five "mons" in order to save the Earth from imminent destruction. Each mon is hidden somewhere in one of the accessible areas of the world and takes a lengthy subplot to complete, except the Talanzaar mon. The latter is hidden inside the Big Bad's palace and thus is only obtained in the linear endgame, which is triggered by collecting the four others.
- OutRun, which uses an exclusive branch structure:
- The SEGA Ages 2600 version of the original OutRun features an Arrange Mode where the stage map is shaped like a diamond rather than a pyramid: For the first half of the game, each stage end has a 2-way fork, but at the halfway stage the stage branching starts to collapse until you reach the same final stage no matter which set of stages you took up to that point.
- In OutRun 2019, Stages 2 and 3 have branching routes like the other stages, but only one choice of a final route. Stages 1 and 4 downplay this trope, each giving you two choices of a final route.
- Jedi Knight: Jedi Academy combines complementary branches with a Fractional Winning Condition: after the prologue and after every story mission, you are given a choice of five side missions and have to complete any four of them to unlock the next story missions (though you still have the option to complete the fifth side mission for an extra Skill Point).
- Each act of the Campaign mode for Unreal Tournament III (sans for the disguised tutorial Act I and the final act, where there's only one, inconsequential branching) has exclusive branches. There's a bunch of missions which are common to each branch, and then the players take paths towards each act's end depending on the choices the player make. Also some paths have useful cards which may be lost depending on the taken path. For example, Act II: With Caesar's Coin involves both taking control of Axon-guarded territory as well as fend back a wave of Krall attacks as the act advances. The first choice is whether to go full all-in on Axon or reinforce the defenses, while the last choice is usually whether to accept Axon's rendition and absorption of the Iron Guard onto the Izanagi forces, or just wipe out the Iron Guard and take their assets.
- This is the bread and butter of the "robotics" timelinenote of the Mega Man Franchise. Most instances in the Classic series has Eight (or fewer) Robot Master stages available from the get go; the Fortress Stages are only available once all of the active Robot Masters have been defeated. The X series and Megaman Zero 1 add an Intro Section to the standard formula.
- Mega Man 3 Remixes 4 of the Robot Master stages and plops them in after the original Robot Master Stages. Once you beat those, you have to fight Break Man before going to the Fortress.
- The structure of the Rockman World games note is as follows: First set of 4 Robot Masters, mini-stage where the game's Dragon (usually) makes an appearance, 4 more Robot Master stages,note final part of the mini-stage wherein The Dragon is fought, Wily Fortress. Add an Intro Stage, swap out the Dragon for Dr. Wily himself in the mini-stage, and skip the "last portion" prior to the Fortress,note and you have Mega Man 7 & 8. Mega Man X4 and X5 have a similar formula to 7 & 8.
- Mega Man & Bass is an interesting animal. Even though it starts with an intro level, and the Fortress is inaccessible until you beat all 8 Robot Masters, only 3 are available immediately after the Intro Stage, 3 of the others require beating a particular 1 of the first 3 each, with the other 2 set between these latter 3 in the Campaign Tree, allowing 2 ways to get to them.
- Shovel Knight has the map sectioned off into quarters, with all but the lastnote occupied by members of the Order of No Quarter. In the first quarter, there are only 2 members (plus an intro stage) with 3 members each in the other 2 quarters. The set in each quarter must be defeated to move on to the next set.
- The storyline of Republic: The Revolution regularly branches out into ideology-specific subplots, before converging into unified plots. A complex example happens, for instance, as soon as you arrive in the second city, Pugachev: not only do you have to complete one of three mutually exclusive subplots to gain a foothold in the city (form a criminal syndicate for Force ideology, a Fake Charity for Influence, or a business network for Wealth), but whatever subplot you pick is also a complementary to the one where you have to expose the corrupt Mayor. Only after you've established your foothold and brought down the Mayor does the overall storyline progress.
- In Alter Aila, you make one choice after the opening mission that determines your initial path. Then, at the end of Act I, you make a second choice to stay on your initial path or switch paths for Act II. There's also a hidden route that modifies the end of Act I and throws Act II off the rails, leading to a different story structure.
- All Dark Souls games are built around complementary branches, giving you a quest to defeat four powerful bosses, each found at the end of one of the respective game's major areas. Said quest usually occupies the middle bulk of the game and is preceded and followed by largely linear sequences of objectives (except in the first game, where the first act also contained two complementary branches between the Undead Asylum and the Sen's Fortressnote ).
- Fire Emblem: The Sacred Stones: Ephraim and Eirika split into exclusive branches after chapter 8, and you can follow whichever one you like. They reunite in chapter 15, and the plot after that is largely identical, but the twin you followed in the midgame has more focus for Character Development.
- The "complementary branches" variation has long been a part of the so-called "BioWare formula":
- Knights of the Old Republic started off on Taris and Dantooine, before opening up and letting you search for Star Maps on Tatooine, Kashyyk, Manaan, and Korriban. Finding all Star Maps revealed the location of Rakata Prime and the Star Forge, where the finale took place.
- Jade Empire opens with a linear chapter in Two Rivers, before splitting up into three plotlines in Tien's Landing, where you have to resolve the crisis caused by the opening of the Great Dam, to wipe out Gao the Greater's den of pirates, and to lift the haunting of the Great Southern Forest. After all three are complete (in any order), the Spirit Monk travels to the Imperial City, where the story again splits in two, where they have to impress the Lotus Assassins by either reaching the top tier of the Gladiator Subquest, or by performing some dirty work for their Inquisitor branch — except you only need to complete one objective to proceed, but can then do the other for the extra XP. After that, the game proceeds pretty much linearly before it reaches the Multiple Endings.
- Mass Effect started off on Eden Prime and the Citadel, before telling you to search for clues to the Big Bad's end goal. After finding the Plot Coupons on Feros, Noveria, and Virmire, and recruiting Liara T'Soni to help you make sense of them, you learn the location of the planet Ilos, where you finally catch up with the Big Bad to duke it out in the final battle.
- Dragon Age: Origins is a bit unusual in that it kicked off with Multiple Game Openings (the eponymous Origins), i.e. exclusive branches, before bottlenecking all subplots for the Battle of Ostagar and the Lothering sequence. After that, however, you are tasked with securing alliances in each of four major areas of the game (the Circle Tower, Redcliffe, Brecilian Forest, and Orzammar), and doing so triggers the unified endgame sequence where you take down the treacherous regent and destroy the Archdemon. The Expansion Pack, Dragon Age: Origins Awakening similarly had you take control of Vigil's Keep, then clean up the surrounding areas, which reveals the location of the Hidden Villain, whom you battle in the endgame. Before that, however, the expansion does an exclusive branching, forcing you to defend either your Keep, or the nearby City of Amaranthine from the villain's armies.
- Mass Effect 2 is even looser with its complementary branches than the usual BW formula requires. Each major mission (Dossier or Loyalty Mission) after the tutorial takes place in a separate level, and the first bottleneck occurs when you complete any four of them (without DLC, they are the four initial Dossiers, but Zaeed and Kasumi's loyalty missions can take their place) and the game forces you into the Horizon Plot Tunnel. Then, it's back to the complementary branches, but after four more, you are again bottlenecked onto the Collector Ship. From there on, however, the player is free to trigger the endgame at any point, so, technically, the final Suicide Mission is just another complementary branch, as the game doesn't end even after completing it.
- Dragon Age: Inquisition does both variants: in act one, you have to choose between exclusive branches of allying with the Templar Order or the rebel mages, forfeiting the other faction to the Big Bad for the rest of the playthrough, while in act two, you must resolve the Grey Warden insurrection and the Winter Palace assassination plot (and with it, the Orlesian Civil War), before you can proceed to the largely linear act three and finish the game.
- The Witcher 2: Assassins of Kings became notable for having the story essentially split in two separate games (exclusive branches) early on, which don't reconverge into a unified plot until the final chapter.
- Saints Row and Saints Row 2 both followed a complementary branches-based formula where you started off with a few linear missions introducing you to the game, before being tasked to dismantle three rival gangs. While each of these three (six, if you count both games) arcs is linear, you can tackle them in any order and even switch between them after finishing each mission. After defeating all three gangs, the respective game wrapped up with another short linear sequence of missions leading to the ending. Later installments largely abandoned this structure in favor of tackling rival gangs in a fixed order mandated by the plot.