This paper is part of an experimental approach aimed at studying the nature of videogames, trying to define what "gameplay" is. The first step of our methodology is to elaborate a classification suited to videogames.
We could consider videogames as applications interacting with players:
According to Chris Crawford the interaction between a player and a videogame can be perceived as a dialogue: "A cyclic process in which two active agents alternately (and metaphorically) listen, think and speak."
Within this paper, we will focus on the "machine" side of the cycle: for now, we won't study the player's role in the construction of a gaming situation.
If we isolate the "computer" part of the videogame interaction cycle, we obtain a simple structural diagram divided into three parts: "Input", a collection of devices allowing the user to express choices. These choices are then evaluated by the rules of the "Compute" part, in order to produce a "result". This result is finally communicated to the player through "Output" devices.
Our approach is deeply influenced by the work of Propp, who raised a formal classification of Russian fairytales. As the usefulness of narrative concepts to study videogames is still controversial, please notice that we only borrowed the methodology from Propp's studies, not his results.
Indeed, Propp's methodology can be viewed as an interesting way to study any corpus from a formal level of analysis.
We then chose to apply this methodology to videogames, in order to try to identify formal aspects in our corpus.We especially focused on the study of videogames rules, which are managed by the "Compute" part.
Our previous researches have shown strong recurrences within rules of a large number of videogames. These recurrences are exposed in the first part of this article. In the second part we will analyze these recurrences and try to draw an formal definition of "gameplay".
In accordance to the methodology used by Propp, we have developed a tool, named "V.E.Ga.S." (Video & Electronic Games Studies), that will allow us to index and to analyze a large number of videogames.
We hoped this tool could help us observe eventual recurrent aspects likely to become criteria of a classification.
We based our analysis on a as large time range as possible, in order to limit the influence of technical evolution on the results we may observe.
With this tool and a list of 588 videogames, we propose a first step for the development of a classification criterion: we have emphasized "Gameplay bricks", a kind of "fundamental elements" whose different combinations seem to be able to cover the gameplay of videogames.
After analysis we noticed that every "Gameplay brick" represents a "recurrent diagram" within the rules of videogames. For example, in two games such as "Pacman" and "Space Invaders" we will find the following kind of rules:
We notice a very strong similarity between these rules and we can therefore consider they are both built on the following template: "If player element does not avoid an hostile element, then there is a negative feedback towards the player element."
Hence, this diagram is the definition of a "Gameplay brick", the AVOID brick. For now, we have identified ten "Gameplay bricks" built upon the same principle.
For example, the "Gameplay bricks" featured in "Pac-man" are: "MOVE", meaning player can move an avatar, "AVOID" for the Ghosts you have to avoid, "DESTROY" for the dots you have to eat, and "MATCH" because you have to match each dot's spatial position to destroy it.
But you can also find these bricks in a racing game such as "Need for Speed Carbon": MOVE a car, AVOID opponents, and MATCH on checkpoints you have to DESTROY. When reached, a checkpoint becomes "out of the game" and is not reachable anymore, so it can be considered as "destroyed" just like any dot eaten by Pacman.
Nevertheless, if you look closely, these two games are still different: Pacman moves in two dimensions while you drive the car in a three-dimensional city, the way ghosts chase Pacman is different from opponents car behaviour in Need for Speed...
Differences between these games are related to two issues:
We then had to limit the number of Gameplay bricks, by trying to identify the most recurrent rules diagrams within our corpus.
Besides the recurrent factor, we also took in consideration the nature of rules: we focused our efforts on rules related to player actions.
Nevertheless, the total number of "combinations" obtainable through these bricks remains quite large.
Interestingly enough, we have noticed that some couples of bricks were found very often in a large number of games.
We named those couple of bricks "Metabricks" and after the study of games featuring one or two "metabricks", we gave them quite meaningful names: MOVE and AVOID became "DRIVER", while the association of SHOOT and DESTROY became "KILLER".
These "metabricks" seems empirically related to the core challenges proposed by videogames. Hence, they are the second component of our classification: they can classify the families obtained through the use of "Gameplay Bricks".
Two families featuring the same metabricks and also some different bricks seem to present a variation of a same core challenge. For example, the families of the games "Pacman" and "Frogger" have a difference on the DESTROY brick: Pacman has to swallow pastilles and thus to destroy them, whereas Frog's only objective is to cross a busy road.
To summarize, we have identified "Gameplay Bricks" representing "recurrent rules templates" within videogames. According to these bricks, we have elaborated a classification based on "families" of videogames. A "family" gathers games with identical "Gameplay bricks" combinations. These families can then be classified upon the presence of some pairs of bricks named "MetaBricks" in their bricks combination.
Our classification raised several "recurrent rules" within videogames, which seems to be an interesting first step to study videogames rules. We will now focus on these "recurrent rules", and try to analyze them by looking back to the definition of a game.
We start the second step of our analysis with the definition of a game according to Katie Salen and Eric Zimmerman: "An activity with some rules engaged in for an outcome".
Hence, Salen and Zimmerman consider a game as an activity defined by two elements: the rules and the result, the latter one coming from a previous goal.
If we consider that a videogame takes place in a virtual universe, we can also consider that this universe is composed by several "elements", in the broadest sense.
For example, in soccer, a game that can be played both as videogame and as sport, the universe is composed by the different elements featured in a match: players, pitch, goals and ball.
All these elements are driven by the "rules" of the game, alike the elements that constitute our own universe are driven by physical and behavioural laws.
From a "soccer" point of view, these rules are the physical rules defining the movement of several elements, for example the gravity applied to ball and players. But soccer rules also feature loads of "game rules", such as the one specifying that only the goalkeeper can use his hands to touch the ball.
All these rules together seem to build a "field of possible actions" that may happen during a soccer match. Salen & Zimmerman call it "the space of possibility".
According to the definition above, a game proposes an outcome. Talking about an outcome imply judgment of the player performance. But in order to judge, you need a reference. In a game the reference is defined by the goal that the players have to reach.
For soccer, the goal of the game, identical for each team, is to bring the ball into the goal of the opposing team. The "goal" and "goalkeeper" words are thus very explicit.
We can also consider the goal of the game as a rule, a special rule of course: this rule will simply have to state "endgame", by announcing the outcome when some conditions are fulfilled.
In our soccer example, the game is "reset" when the ball enters into one of the goals, and the score of the team who thrown the ball in is increased by one point.
Even though a match usually lasts 90 minutes, the game outcome isn't only related to time: the winning team is the team with the highest score after 90 minutes of play.
Hence, the outcome of a soccer play is tied to the goal of this game, which is to throw the ball into the opposing goal.
If the goal of a game is also a part of the game rules, does it means different "kinds" of rules exist?
The work of Gonzalo Frasca seems to indicate so, especially the typology of videogame rules he proposed :
For now we will put aside the "Metarules", which leads us to the following conclusion: within rules of a game, some rules define a goal while other rules offer means to reach it.
As different kinds of rules exist, and as "Gameplay bricks" are based upon "rule templates", the following question emerges: On what kind of rules are the bricks based on?
By analyzing the diagram of each Gameplay brick, we observe several characteristics shared by two distinct groups of bricks. Indeed, we may divide bricks into two categories.
The first category of bricks seems to be based on a principle that one would formulate in the following way: "to listen to Input and consequently to carry out modifications on the game elements".
The second category would rather correspond to: "to observe the game elements in order to return an evaluation of the quality of the previous modifications".
We here find principles very close to two of the types of rules evoked by Frasca: the first category approaches the definition of "Manipulation rules", whereas the second seems to be related to "Goal Rules".
But, from our point of view, the difference between these two categories of bricks is linked to the difference between the two terms "Play" and "Game".
Indeed, the bricks of the first category, as they are related to Input, can be connected to the word "Play", whereas the bricks of the second category are related to the goal and by extension to Output, and so are rather related to the word "Game".
The difference between bricks of the two categories appears all the more clear when considering they are not in direct relation: the two categories of bricks "interact" trough "game elements": "Play" bricks modifies them, and "Game" bricks observes the modifications made by the first ones.
Moreover, if we look back to the "Metabricks", namely DRIVER and KILLER, we notice that they are composed by a "Play brick" associated to a "Game brick":
As these "Metabricks" represents pairs of "GamePlay bricks" that we identified in a large number of videogames, we propose the following definition of gameplay:
"Gameplay is the association of "Game rules", stating a goal to reach, with "Play rules", defining means and constraints to reach this goal."
In order to analyze the nature of videogames, our approach focuses on game rules.
Being inspired by the methodology that Propp used for his fairytales classification, we started a quantitative analysis of videogames.
This methodology allowed us to elaborate a classification based on "recurrent templates of games rules". These templates are formalized into an element called "GamePlay bricks". We are then able to group videogames into "families" featuring the same combination of "GamePlay bricks".
We also observed that some couples of bricks were found recurrently in the bricks combination of games we observed. We baptized these pairs of bricks "Metabricks", as they allow us to classify families of videogames.
We then used these "GamePlay bricks" and the rules behind them as a basis to propose a formal definition of what gameplay is, from a rules point of view.
Starting form the definition of a game proposed by Salen & Zimmerman, we identify two elements in a videogame : the rules and the outcome.
After analysis, we can relate these elements to two kinds of rules proposed by Frasca: "rules" seem related to "Manipulation rules", defining what the player can do in a videogame, whereas "outcome" seems connected to "Goal rules", defining an objective the player has to reach in order to win the game.
By analysing the rules defining our "GamePlay bricks", we observe two kinds of bricks: "Play bricks", related to "Manipulation rules", and "Game bricks", related to "Goal rules".
We then obtain a draft typology featuring two kinds of rules, namely "Game" and "Play". As we also observe that "Metabricks" are composed by a "Game" brick associated to a "Play" brick, we propose the following definition for gameplay:
"Gameplay is the association of "Game rules", stating a goal to reach, with "Play rules", defining means and constraints to reach this goal".
The "bottom-up" approach will involve the verification of this typology by the realisation of an "experimental game" based on this conceptual model.
Named "Gam.B.A.S.", we presented a first prototype of this game based solely on "Play" and "Game" rules in a previous article. We now have to add in "World" rules and see what games can emerge from this experimentation.
The "top-down" approach will be based on "V.E.Ga.S." and the videogame classification presented here, but with a much larger corpus.
We are modifying our videogame indexation tool, in order to propose a collaborative version of our videogame classification, freely accessible on the Internet.
You might then freely propose, evaluate or even consult information about any videogame on the following website:
Authors wish to thank Jean-Yves Plantec and Martial Bret from "Iode" Company, for their point of view on the concept of "brick", as well as Stéphane Bura, Art Director at 10Tacle Studios, who directed us toward a great number of references.
We also offer many thanks to Annika Hammarberg for the translation of this paper from French to English, and to Rashid Ghassempouri for his general help and thoughts in our earlier works about the videogame classification.
 Crawford C., "Chris Crawford on Game Design", New Riders, 2003.
 Salen K., Zimmerman E., "The Rules of Play", MIT Press, 2003.
 Djaouti D., Alvarez J., Jessel J.P., Methel G., Molinier P., "Towards a classification of videogames", AISB2007, Bristol - Scotland, 2007.
 Alvarez, J., Djaouti, D., Ghassempouri, R., Jessel, J.P., Methel, G., "Morphological study of the video games", CGIE2006, Perth - Australia, 2006.
 Propp, V., "Morphologie du conte", Seuil, 1970.
 Frasca G., "Simulation versus Narrative: Introduction to Ludology", in The Videogame Theory Reader, Routledge, 2003.
 Djaouti D., Alvarez J., Jessel J.P., Methel G., Molinier P., "The nature of gameplay: a videogame classification", Cybergames2007, Manchester - United Kingdom, 2007.