FUNDAMENTALS OF GAME DESIGN, SECOND EDITION
Core Versus Casual
The most significant distinction among player types is not between console-game players and computer-game players, nor between men and women, nor even between children and adults. The most significant distinction is between hardcore (usually just shortened to "core") gamers and casual gamers.
Core gamers play a lot of games. Games are more than light entertainment to them; games are a hobby that demands time and money. Core gamers subscribe to game magazines, chat on game bulletin boards, and build fan websites about their favorite games. Above all, core gamers play for the exhilaration of defeating the game. They tolerate frustration well because of the charge they get out of finally winning. The greater the obstacle, the greater the sense of achievement. Core gamers thrive on competition. They don't like games that are easy; they like games that are challenging.
By comparison, casual gamers play for the sheer enjoyment of the experience. If the game stops being enjoyable or becomes frustrating, the casual gamer stops playing. For the casual gamer, playing a game must be entertaining, whether it's competitive or not. A casual gamer is simply not willing to spend hours learning complex controls or getting killed again and again until he finds the one weak point in an otherwise invincible enemy; he feels that he has better things to do with his time. To design a game for casual gamers, you have to give them a sense of rapid progress and achievement.
In reality, of course, there are as many types of gamer as there are games; everyone has a reason for playing computer games. But the casual/core distinction is a very powerful one. If you design a game specifically for one group, you almost certainly won't have a lot of sales to the other group. A few very well-designed games manage to appeal to both: Goldeneye, for example, can be played happily by both core and casual gamers. Core gamers can set the game at the highest difficulty level and drive themselves crazy trying to cut 15 seconds off the last time it took to play a mission. Casual gamers can set the game at the easiest level and blast away, enjoying the game's smooth controls and visual detail.