https://www.learningresources.com/product/learning+essentials--8482-+stem+robot+mouse+coding+activity+set.do My kids lost the cheese piece that came with this game, so.... I had to 3D print a replacement. The part is hollow so that you can pause the print and drop a magnet in it. I used a 12mm x 3mm magnet that I bought from Home Depot. I didn't have any yellow filament, so I used "gold" filament from Makers Geek. DRAGONS METALLIC PLA - ALL THAT GLITTERS GOLD https://youtu.be/vPY6xjDjqXY