What is a game mechanic? There are several definitions. All of them different. As a game designer and teacher I have been frustrated with the vagueness of the term. If you are interested in the current discourse about game mechanics you may wish to check these out:
Wikipedia: Game Mechanics
Defining Game Mechanics
Game Development Essentials: Gameplay Mechanics
Introduction to Game Development, 2nd Edition
The purpose of this post is not to identify or define game mechanics but rather explore the most basic structure of the game mechanic. I term this structure as the game atom. The game atom represents an essential pattern within all game mechanics.
The game atom exits out of five main elements. These being objects, attributes, procedures, players, time and space. Objects are often represented in games by avatars, enemies, traps, bosses, units, weapons, ammo, power-ups, pick-ups, etc. All objects have a number of attributes, which determine or influence the speed, health, damage, life, ammo, etc. of the object to which they are attached. Objects and their attributes interact through procedures, which can be related to actions or events in a game such as select, move into, trigger, shoot, hit, punch, kick, take damage, pick-up ammo, game over, etc. Procedures can also be designed to stimulate social interaction between players, which is essentially a second order procedure that only the players can resolve. Examples of social procedures would be multi-player, cooperation, voting, biding, etc. Players represent either people or some sort of heuristic or procedural A.I. (artificial intelligence), which then determine the control of related game procedures, objects and their elements. Finally, these elements exist with the constants of time (turns, timed limits, rhythm, rate of fire, delay after attack, etc.) and the limits of the space (location, worlds, maps, boards, fields, levels, screens, etc.) that they occupy.
Together all these elements represent what I have termed the game atom. Beyond attempting to describe the most basic elements of a game mechanic, this model forms the framework for my flowcharting and design document methods. The game atom is also the first layer in my model of understanding game design, which I call the aims of game design. Besides game mechanics, the ‘aims’ also include the play mechanics and game-play experience layers.
The game atom is a practical tool and it can help map out game mechanics. Game mechanics themselves have a tremendous variety and even small variations in seemingly like mechanics can be seen as entirely different mechanic. We must realize that the game mechanic is actually a subjective attempt at describing some of the recurring patterns that can be found in game design. If you are interested in a catalog of these patterns I suggest reading Patterns in Game Design (Game Development Series)by Bjork and Holopainen.