This paper considers the increasing utilisation of games design as an approach to encouraging behavioural change through design. In particular it considers how to address issues that cannot be reduced to easily actionable personal goals such as climate change and are often termed ‘wicked problems’ by designers due to their innate complexity. This paper presents a research through design approach that focuses on rhetoric within the design of a mobile phone game - Cold Sun. Thus the aim is not to examine the utility or usability of the game but rather offer it as an example of a design approach we believe is desirable and productive for future practice. Cold Sun provides an example that illustrates how scientific and real world data can be integrated into game mechanics to enhance the rhetoric of the game by engaging the player at a more personal level. Thus Cold Sun allows players to effectively rehearse issues of climate change that will affect their plausible futures, and thus develop a greater understanding of some of these complex issues and consider ways to respond.