There are various types of video games, which includes arcade games, computer games, console games, handheld games and mobile games. As computer technology develops, a game becomes more realistic and it encourages more people to play the game. Video game industry is one of the fastest growing industries; the size of the game industry was about $9.5 billion in 2007, but it is valued at over $93 billion in 2014, according to Gartner (Wikipedia, "Video game industry"). When we look at the history, we can see that the history of video games started from the arcade games. The biggest reason should be the lack of technology; as the size of the computer was huge at first, it is obvious that the game console should be big to provide complex games that are fun enough to attract the players. As the technology developed, the companies produced game consoles small enough to be playable at home. When the personal computer became affordable to everyone, video game companies modified console games to PC games or developed a new game for PC users, who may not want to buy a game console only for playing games. Handheld games and mobile games were developed to satisfy players who want to play games whenever they want, although the graphics and complexity of these games should be inferior to those of console games or PC games.