Student fluency in mathematics is important, as fluency supports mathematics proficiency and achievement. While fluency can be supported with flashcards and worksheets, it can be supported by games. In this exploratory study, researchers examined the relationship between students' fluency on addition with regrouping problems and playing a virtual Make 10 s game, which supports the making tens strategy for addition. After seven sessions of playing the virtual Make 10 s games, researchers found Tau--U effects from the single case design study were high for at least three of the four students. Yet, researchers were unable to conclusively determine if a functional relation existed between student accuracy for digits and answers in solving the single--digit addition with regrouping problems within one minute and students playing the virtual Make 10 games.