In this presentation, issues of planning game design for transfer and assessment are discussed. A review of the role of play is provided in relation to game design. Play can be part of a problem because of the lack of certainty in learning transfer. Serious games are developed to deliver learning outcomes. When there are specific learning outcomes, the game must make sure that learning that happens in games, does not stay in games. This is described here as the Vegas Effect. A simple methodological recommendation with examples is provided for improving validity and reliability in the independent variable (game interventions). This is known as inter rater reliability.