Devlin in [7] argues that video games are an ideal medium for the teaching and learning of mathematics, though he points out that very few 'good' mathematics video games exist.1 Building on a probabilistic board game developed in the 1980s, we created a mathematics computer game, E-Brock Bugs. The design of the game carefully follows Devlin's principles of a good mathematics video game, including a well-developed storyline, the selection of an in-game avatar, and an environment where mathematics arises in a natural and meaningful way. As a result, we argue that E-Brock Bugs is an epistemic computer game [1]; it goes beyond teaching basic facts and skills, and may encourage the players' development of mathematical thinking as 'working mathematicians'.