There are in-fact a lot of challenges to overcome when designing a computer game. First of all, there is the challenge of coming up with the initial concept and thus the concept document (the document specifying the bare bones of the concept: game mechanic, world, characters, audience and it's market appeal). During the conceptual proccess there will also be other members of the team working on concept art for characters and levels, as well as storyboards for cut-scenes. Concepts for levels may occur during either the first or second phase. During the second phase of design we begin to enter the iterative design proccess, wherein the design document is created (a more specific document, which details some of the AI and more specific elements of game play, such as what methods of control, etc, level specifics). The iterative proccess is where the game is designed, then tested, then adjusted after play-testing, then play-tested again and developed thusly. During the second phase the level and mechanics are the main focus, and the characters in the game are usually only place-holder art/models. This is when the technical document will start to be written (this is predominantly the domain of programmers). It is during the end of this proccess that models are polished off for the level and characters and that sound begins to be recorded for the game (although it will already have been considered in the first stage). The third stage is predominantly about polishing off the product and starting the marketing proccess: coming up with trailors, posters, etc. The six main groups of people in the production proccess are: Games Designers (work on the concept document and design document, as well as possible level concepts (it is also worth mentioning that a lot of games designers have other skills, usually art, so will help with the art side too)), Artists (work on concept art, storyboarding, some are also able to model and animate, thus will also take part in these proccesses), programmers (obviously work on the code for the mechanics, code-monkeys are also needed to program in the sound/music), modellers (create the 3D assets: the characters, buildings, etc, and animate them usually, although not all modellers are skilled in animation), animators (animate the models), sound designers (create the music and sound effects).