We present a concept of a fitness game that can be installed in public places and encourage passers-by to participate in a short play. The game is controlled by players' body motions and thus provokes physical exercises. Moreover, the game encourages social interactions between players, if played in multi-user mode. To play the game a person needs a mobile phone with accelerometer. We describe the game design based on engagement theories and the first evaluation results. The game can beneficially combine physical exercises and social interactions in a playful way. Categories and Subject Descriptors H.5.2 [User Interfaces]: Interaction styles, input devices and strategies. General Terms Design, Human Factors. Keywords Physical activity, social interactions, engagement, fitness games.