Game mechanics which are
Of the various ways of categorizing different kinds of gameplay mechanics and how much freedom they afford the player, one of the most basic is how "shallow" or "deep" they are. Supposing you have two games which both feature some form of telekinesis. In the first, the mechanic is entirely combat-focussed and the player can only use it to lift up enemies and strangle them in mid-air - no other usage is possible. In the second game however, the player can use the mechanic to kill enemies in a much wider variety of creative and sadistic ways, disable security cameras should the player wish to play stealthy, create diversions and stack objects on top of one another in order to climb over walls. The first game's core mechanic is hence "shallow", as it has only one function and can only be used in one context, whereas the latter's is "deep", as it more fully explores the possibilities of the mechanic and allows the player to use the same mechanic in a number of different contexts and to achieve different results. A game does not qualify as having deep mechanics if it has a large number of game mechanics each of which can only be used in one way. It is specifically about exploring the various possibilities of individual mechanics. Note that Tropes Are Tools and this is not for Complaining About Shows You Don't Like: many of the most popular games made have simple, one-dimensional game mechanics, whereas some players may be turned off by overly complex and finicky game mechanics or simply find that they never use half of the functions. The more freedom a player is afforded in exploring the possibilities of a mechanic, the more developers run the risk of running into a Combinatorial Explosion (conversely, many developers may use this as an opportunity to demonstrate that The Dev Team Thinks of Everything).