Right or left - that's the question here! Because the direction in which the wheels turn depends entirely on the speed of the balls. Suddenly, physics is more exciting than ever! Those who build skillfully can combine the two differently sized wheels into a kind of gear system. This allows for surprisingly great effects. Together with the additional parts, this set extends the length of the track and offers an extra dose of tinkering fun. Here, the ball spins on the wheel! The quick guide explains how to make the best use of the two wheels in the marble run, and then you're ready to go. Get to work and build anywhere it's smooth and vertical! An innovative extension of the KOSMOS Gecko Run for even more experimental fun for all children aged eight and up. Note: Playable only with the KOSMOS Gecko Run "Starter Set" or the "Big Box.".