During a two week period of very cold weather and lots of indoor recesses, I created this math game for my second graders. The idea was to help my students understand function boxes and although they thought it was entertaining watching me do an “in the box, out of the box“ impersonation, they much preferred jumping out of a box themselves. I put some wrapping paper on a big cardboard box and made a giant bow from construction paper and named the game, “What’s My Rule?” We had been learning about function boxes and this game gave them some repeated practice. It would work great in a math center or some small group work. This resource includes full-page numbers 0 – 20, printer-friendly and color worksheets in two themes, winter, and elves with presents. Once students have their worksheets filled out, they choose one of their function boxes to use and gather the laminated numbers. Classmates will try and guess the rule by watching the numbers and figuring out the pattern. A wrapped box isn’t necessary for the game, students can just stand up or down from behind a desk or table to impersonate the function box.