With the rapid growth of recent smart phone technology, the interests for the design of online game in mobile computing environment are highly focussed on with great attention. Smart phone as a mobile terminal device, however, has many restrictions for implementing online mobile game since the limitation of relatively low performance of a processor, low resolution of GUI, small memory spaces, and short battery power. Therefore, most of games are very restricted on online and multi-play functions. In this paper, we design and implement mobile online game app in component based smart phone environment in order to take over these restrictions in mobile environment. Especially, the implemented mobile game is able to play online game among Wi-Fi based game server and another smart phone.