Movement from one part of a game world to another which cannot be reserved or where the return takes a disproportional amount of effort.
When movement for a game element in a game cannot be undone easily this movement is a One-Way Travel.
The pawns in Chess can only move forward, although also diagonally so when doing normal or en passant capturing.
Arcade Games such as Pac-Man and Donkey Kong that consist of levels have One-Way Travel between these, and so does the First-Person Shooter games in the Doom and Quake series (Hexen was the first to not have this). Scrolling Computer Games such as 1942 and Zaxxon forces players into a One-Way Travel at a certain speed although players may have some leeway in both horizontal and vertical position on the gameplay area. For those games that loop back to the first level at some point (instead of generating new levels indefinitely) still provide a One-Way Travel since the lack of effect players have on the revisited levels make them effectively new ones.
Leaving the city of Kirkwall to join the Deep Roads expedition in Dragon Age II is effectively a One-Way Travel even if one later returns to the city. This since the return will start a cutscene progressing the storyline and changing what quests are possible there.
Using the pattern
One-Way Travel can be designed in two fashions: pure which means that players never during a game instance will be able to return, and local which means that players can actually return but have to do it using another route which takes more time or effort. The pure variety is typically used to help maintain Predetermined Story Structures or to create Leaps of Faith. The simplest way to provide local One-Way Travel in games is probably height difference sufficient to hinder ascent but not killing those that decent. Implementing pure One-Way Travel may in contrast simply consist of not designing for actions that let players return to previously visited places after they have been moved to new places through Facilitating Rewards; it can be explicitly design for by using The Show Must Go On in Real-Time Games to force Movement of players' Avatars (technically it may be the presentation of the Game Worlds that move).
While Transport Routes can simply be designated as only supporting One-Way Travel (e.g. by Vehicles that can only travel in one direction), it can also be explicitly created through blocking returns by introducing Obstacles that appear as Irreversible Events after one has entered specific areas of Levels or Game Worlds. Have game elements begin or be created in Inaccessible Areas and letting them leave these but not re-enter them is another way to create One-Way Travel.
In games including much Movement, the One-Way Travel may be limited to noteworthy forms of Movement such as Quick Travel or Warp Zones, or to situations where it creates specific gameplay choices in the form of Leaps of Faith. They can be used on Flanking Routes to make players have to commit themselves to one approach out of several.
Often being designed through the use of height differences, Galleries can provide One-Way Travel to those in these.
Since One-Way Travel can be used to create Irreversible Events, they can be tools for ensuring that Predetermined Story Structures are unfolded in a certain way as long as they depend on changes in physical location. Since they quite often represent travel over long distances or significant jumps forward in diegetic time, they are quite often modulated by Cutscenes.
Travelling back to areas previous visited to not have to be incompatible with pure One-Way Travel. The pattern concerns gameplay, so if players can return to a part of the Game World but the gameplay has changed even if only being distinctly close to some high-level closure the pattern still holds. Diegetic changes probably need to be made in these cases to uphold Thematic Consistency but these can be motivated even after a brief period of gameplay through use of Cut Scenes.
Pure One-Way Travel is a way to make Movement in Game Worlds or Levels into Irreversible and Ultra-Powerful Events. As such, it makes Reversibility impossible and this can be used to guarantee at least location in Predetermined Story Structures. It can make Herd goals easier since it effectively divides this goal into a Goal Hierarchy.
When return is possible but cumbersome, One-Way Travel instead requires players to make Trade-Off decisions between the value of moving forward and the cost of possibly having to return. Both types of One-Way Travel are examples of Conditional Passageways.
Can Be Instantiated By
Can Be Modulated By
Possible Closure Effects
Potentially Conflicting With
New pattern created in this wiki.