Energy reduction is one of the main challenges that countries around the world currently face, and there is potential to contribute to this by raising awareness towards sustainability in the workplace. We introduce IdleWars, a pervasive game played using smartphones and computers. In the game, workers' pro environmental or wasteful behaviour is reflected in their game score, and displayed through ecofeedback visualisations to try and call attention to energy wastage and potentially reduce it. We conducted an initial deployment for two weeks in an open plan office, and observed that the game dynamics works in terms of engaging participants and drawing their attention to the pro-environmental behaviour.