A great many people play online games and sales of online games are considerable, but research has further shown that a major reason behind the failure of games in the market is poor user interface design or usability, highlighting even more the importance of these issues in games design. This research uses surveys and focus groups to explore the factors influencing the usability and interface design of online games. First the definition and different types of game are discussed, and then the composition and features of online game interfaces analyzed. Second, a review is made of Human-Computer Interaction (HCI) research literature relating to design criteria for game interfaces. Finally, in discussion with experts, this study isolates the design criteria that should be emphasized when designing each key element of an online game interface.