Human Intelligence Instead of Artificial Intelligence
In single-player games, the player competes against the computer, so the computer has to have enough artificial intelligence (AI) to be a good opponent; building the AI for a complex game presents a huge programming task and one that is difficult to get right. But if the players compete against each other, as they do in most online games, you don't usually need as much AI. The players provide all the intelligence required in many situations.
You can use AI in an online game if you want to: You might include nonplayer characters (NPCs) who need to behave intelligently, or you might design a game in which all the players play cooperatively against artificial opponents. Several popular games have limited NPCs but have some large opponents that the online players must work together to combat. Guild Wars, for example, encourages this type of play. The AI-controlled enemies are challenging to beat with a team of online friends and impossible for an individual. But many online games rely on their players to provide most of the intelligence in the game, and this can make the game easier to develop in that respect. A real-time strategy game, for example, still needs AI for its individual units when played online, but players supply the strategic and tactical thinking.