Mathematics games are often used in the classroom as a reward or warm-up activity before the "real" learning takes place. Many teachers have witnessed how useful games are for tuning-in students to the impending mathematics lesson. However, have teachers considered playing games as the central part of the lesson? This article explores the benefits and negative impact of games in the classroom, and recommends a calculator game that encouraged Year 5 and 6 children to challenge their misconceptions of the multiplication and division of decimals. (Contains 2 figures.)