Orthogonal Differentiation

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Differences in abilities of game entities that are in type rather than in value.

One of the uses of having many game entities in games is that they can have different types of abilities. When these abilities and the functionality they provide do not only have quantitative but also qualitative difference this means that the games have Orthogonal Differentiation. This give the different game pieces additional value since they represent the only ways for players to perform certain actions. Not all or many aspects of the game entities need to be unique; often it is sufficient that a single ability is radically different from other units for it to have special gameplay value. In team games, the differentiation may actually be between players so that each player has unique abilities.


The pieces in Chess have different types of movement rules, giving them different gameplay value and giving the game Orthogonal Differentiation.

While most monsters in the Doom series differ in health, speed, or damage dealt, the Pain elemental and Arch-vile have Orthogonal Differentiation in that they have the unique abilities to spawn lost soul monsters and resurrect killed monsters respectively.

Real-time games such as the Age of Empires series and the Command and Conquer series are based around producing and making best use of a wide variety of units. Although few units have unique abilities, such as the converting ability of priests, many do have abilities that are shared by only a few other types of units.

Using the pattern

Orthogonal Differentiation is used in games to either provide more gameplay without increasing production costs or create more Complex Gameplay, or both. The difference in functional Abilities can exist either between different game entities under the same player's control or between those of different players' control. An alternative is to have Orthogonal Differentiation between Enemies. It is achieved through Asymmetric Abilities between Characters or Units. However, Asymmetric Abilities is not enough since the differences need to be in type rather than in degree. Although Privileged Abilities guarantees important differences in Abilities, New or Improved Abilities can also provide Competence Areas; even Ability Losses and Decreased Abilities can be used for this.

Typical areas where Orthogonal Differentiation is used include the ways to do Damage, availability of Skills and Combos, effects of Fog of War, and differences in how Movement can be done due to Privileged Movement.

Player-Avatar Proximity provides Orthogonal Differentiation through making gameplay actions possibly through the movement of either avatars or players.


Orthogonal Differentiation provides more Varied Gameplay for a game compared to one with the same amount of Characters or Units but without distinct differences in Abilities. The difference and the added importance individual game entities may have give rise to Complex Gameplay but also Replayability. When players have control over the game entities with Orthogonal Differentiation of Abilities, making full use of the different Abilities promote Stimulated Planning. In games with Teams and Characters, Orthogonal Differentiation makes the possibility of creating Team Combos likely and through this Team Strategy Identification as well.

The unique abilities required by Orthogonal Differentiation makes it difficult to combine with Symmetry on the same level of game design. This cause also makes Orthogonal Differentiation problematic for Player Balance and Team Balance in games with PvP and TvT gameplay respectively . However, they can be combined by treating the differentiated units as a set and have the same sets for all players or all Teams.


Can Instantiate

Complex Gameplay, Replayability, Stimulated Planning, Varied Gameplay

with Teams and Characters

Team Combos, Team Strategy Identification

with TvT

Team Balance

Can Modulate

Abilities, Characters, Enemies, PvP, TvT, Units

Can Be Instantiated By

Asymmetric Abilities, Competence Areas, Player-Avatar Proximity

Can Be Modulated By


Possible Closure Effects


Potentially Conflicting With

Player Balance, Symmetry

Team Balance in games with TvT gameplay


An updated version of the pattern Orthogonal Unit Differentiation that was part of the original collection in the book Patterns in Game Design[1]. The concept was first introduced by Harvey Smith to game developers at a presentation at GDC 2003, and the presentation is available online[2].


  1. Björk, S. & Holopainen, J. (2004) Patterns in Game Design. Charles River Media. ISBN1-58450-354-8.
  2. Smith. H. (2003) Orthogonal Unit Differentiation. Presented at GDC 2003. Available online.