A system of vision-based mixed reality is developed for implementing outdoor gaming on a mobile device having a single camera and a slow CPU. To help the poor device, it is assumed that sufficiently many marker objects of the same size are scattered in the real world so that relative translation and rotation of the camera can be easily calculated from their position and size in the camera image. This system can be applied to outdoor games of which scenario allows for existence of some items that the markers can mimic.