Play games

We probably all have a decent intuitive notion of exactly what a game is. The typical term "game" encompasses games like chess and Monopoly, card games like poker and blackjack, casino games like roulette and slot machines, military war games, computer games, various kinds of play among children, and the list goes on. In academia, we sometimes talk about game theory, where multiple agents select strategies and tactics in order to maximize their gains within the framework of a well-defined set of game rules. When found in the context of console or computer-based entertainment, the word "game" usually conjures images of a three-dimensional virtual world featuring a humanoid, animal, or vehicle as the main character under player control.  Play games (Or for the old geezers in our midst, perhaps it brings to mind images of two-dimensional classics like Pong, Pac-Man, or Donkey Kong.) In his excellent book,

In a Theory of Fun for Game Design, Raph Koster defines a game title to be an interactive experience that provides the player with an increasingly challenging sequence of patterns that he or she learns and eventually masters. Koster's assertion is that the activities of learning and mastering are in the middle of what we call "fun," just like a laugh becomes funny right now we "get it" by recognizing the pattern.

Most two- and three-dimensional video games are types of what computer scientists would call soft real-time interactive agent-based computer simulations. Let's break this phrase down in order to better know what it means. In many video games, some subset of the real world -or an imaginary world- is modeled mathematically so that it could be manipulated by a computer. The model is definitely an approximation to and a simplification of reality (even if it's an imaginary reality), because it is obviously impractical to include every detail right down to the number of atoms or quarks. Hence, the mathematical model is a simulation of the real or imagined game world. Approximation and simplification are two of the overall game developer's most effective tools. When used skillfully, even a significantly simplified model can sometimes be almost indistinguishable from reality and a lot more fun.

An agent-based simulation is one where numerous distinct entities known as "agents" interact. This fits the description on most three-dimensional computer games perfectly, where in fact the agents are vehicles, characters, fireballs, power dots, and so on. Given the agent-based nature of most games, it should come as no surprise that a lot of games nowadays are implemented in an object-oriented, or at least loosely object-based, programming language.

All interactive video games are temporal simulations, and therefore the virtual game world model is dynamic-the state of the overall game world changes with time since the game's events and the story unfolds. A video game must also respond to unpredictable inputs from its human player(s)-thus interactive temporal simulations. Finally, most video games present their stories and respond to player input in real-time, making them interactive real-time simulations.

One notable exception is in the category of turn-based games like computerized chess or non-real-time strategy games. But even these kind of games usually provides the user with some form of the real-time graphical user interface.

The term "game engine" arose in the mid-1990s in the mention of first-person shooter (FPS) games like the insanely popular Doom by id Software. Doom was architected with a fairly well-defined separation between its core software components (such as the three-dimensional graphics rendering system, the collision detection system, or the audio system) and the art assets, game worlds, and rules of play that comprised the player's gaming experience. The worth of the separation became evident as developers began licensing games and retooling them into new services by creating new art, world layouts, weapons, characters, vehicles, and game rules with only minimal changes to the "engine" software.

This marked the birth of the "mod community"-a number of individual gamers and small independent studios that built new games by modifying existing games, using free toolkits pro- vided by the initial developers. Towards the finish of the 1990s, some games like Quake III Arena and Unreal were designed with reuse and "modding" in mind. Engines were made highly customizable via scripting languages like id's Quake C, and engine licensing began to be a viable secondary revenue stream for the developers who created them. Today, game developers can license a game title engine and reuse significant portions of its key software components in order to build games. While this practice still involves considerable investment in custom software engineering, it could be a lot more economical than developing all of the core engine components in-house. The line between a game title and its engine is frequently blurry.

Some engines make a fairly clear distinction, while others make minimal attempts to separate the two. In a single game, the rendering code might "know" specifically just how to draw an orc. In another game, the rendering engine might provide general-purpose material and shading facilities, and "orc-ness" might be defined entirely in data. No studio makes a perfectly clear separation between the overall game and the engine, which will be understandable due to the fact the definitions of those two components often shift since the game's design solidifies.

Arguably a data-driven architecture is what differentiates a game title engine from a software program that is a game title but no engine. Play games each time a game contains hard-coded logic or game rules or employs special-case code to render specific kinds of game objects, it becomes difficult or impossible to reuse that software to make a different game. We ought to probably reserve the definition of "game engine" for software that is extensible and can be used as the building blocks for a variety of games without major modification.