This applet has been created for didattic purposes for high school students.[br]The student is able to find the condition of pure rolling motion using this app interactively and guessing which are the right interplay between the physical quantities.[br]The app should make the student think about the ratio between the velocity of the center of mass of the wheel and the one of a point on the edge,[br]when the wheel is nor creeping nor slipping, but appear as a real moving wheel that rolls without friction.[br]The app is also intended to introduce the parametric equation of the cycloid.[br]Other physical questions tha could be posed are:[br]How many conditions of creeping are there?[br]How many conditions of slipping are there?[br]What is the pure rolling motion condition?[br]What are the simple equations that relates the physical quantities in the game and describe these dynamic constraints?[br][br]I would like to thank Prof. C. Falcolini (Università di Roma Tre) for the pleasing discussions that gave birth to this app.