It is said that playing video games might make people more creative. There is some evidence of an association, but no so far general theory about any psychological causes, or other key factors. In this study, we test the possibility that different sorts of video games may have different effects, on different types of creativity; or none at all. Three games were tested, including a sandbox and a puzzle game (Minecraft and Portal 2), and creativity was measured by the Torrance Tests of Creative Thinking (TTCT). The games were found to have different effects, and on only some measures. We discuss possible accounts for these results, and offer practical suggestions to better control such studies in future. The strongest and most surprising result was that one particular form of creativity, flexibility, was affected much more than others. This finding awaits a theoretical explanation; but in the meantime, the implication is that video games could be used to put students into a more creative state of mind, which may be useful for their learning.