A single constraint on the possible gameplay actions that determine a part of the player’s experience.
According to our working definition of gameplay, the purpose of a game mechanic is to constrain a game’s interactivity so that it guides the player toward a fun experience. Tuning these contraints is one of the most important game design processes. However, in order to tune game mechanics, it is necessary to understand what mechanics are and how they combine to form gameplay.
First, let’s look at how a single game mechanic constrains the possible actions a player can take. Often these constraints are explicit rules like “If the King is put in check and cannot legally escape, the king is checkmated and the game ends in a loss for that player.” Sometimes they are limits enforced by the simulation; there are some gaps that Mario can only jump while running. The most important constraints are usually determined by the game’s control scheme. After all, the player can only perform actions which are mapped to available inputs.
Another common type of constraint is the player’s objective in the game. For instance, a goal in Pac-Man is to eat all the dots. This limits the player’s behavior because any interaction that does not involve eating dots is irrelevant to the game. This mechanic divides all the entire spectrum of possible actions the player can take into two halves, actions that are permited and those that are prohibited.
Game mechanics guide the player experience by removing some alternatives and emphasizing others, but by itself, a single game mechanic is not a game and cannot lead to a fun experience. In fact, a single game mechanic by itself is barely even interactive. With only one constraint, there is only one option. There is no room for choice or skill or expression. To demonstrate this point, I built a “game” based on a single dot-eating game mechanic.
(My free Flash host can no longer keep up with demand, please click this link to load the example.)
Heh. Just ran across this take on the Pac Thing:
I was amused.