This research explores productive multi-player games as a platform for human-computer agent collaboration. A multiagent perspective is taken to examine the principles of both gameplay and mechanism design for productive games. To engage human players in sustained gameplay, the game agents are designed with the flow and dramatic principles. To ensure productivity, the game mechanism is designed such that rational agents, both human and software, will follow the target strategy to reach subgame perfect equilibrium. The design principles are demonstrated and evaluated using PhotoSlap, a multi-player productive game for photo annotation. Categories and Subject Descriptors I.2.11 [Distributed Artificial Intelligence]: Multiagent systems General Terms Design, Game Keywords Productive game, gameplay, strategy analysis, agent collaboration