Numerous authors have tried to use game theory as a tool for computer game design and study. These works recall generally some basic concepts of the Neuman Mogenstern game analysis (payoff matrix, finite zero-sum game, dominant and mixed strategy...) and show how to model and interpret some simple gameplay situation. In this paper we consider solo games (one player against the computer) and we take the point of view of the game analyst or the game designer. Game theory is either used to understand the gameplay or to build a gameplay. In this case game theory hypothesis arc never met: the computer has all the knowledge and is in charge to disclose the game rules to the player according to a driven progression scheme. But we show that, as the game designer is the creator of the universe of the game, he can choose the rules, the payoff matrices and the laws of the video game universe, that game theory can be a power full tool.