This article initially presents the background and the theoretical framework going along with a research – creation initiative that focuses on the concept of "expressive game", which encourages players to experience various ethical and moral choices, allowing them to understand the consequences of those choices. To do this, a reflection is conducted on the specificities of games as a form of expression around the concepts of ludic mediation, playability and ludic ethos. It will then enable us to show how the exploration of these leads has been integrated in design issues by taking the example of Keys of a Gamespace – a PC game developed by the author of this article.