With The Gravitrax Interactive Track System; You Can Design And Build Your Own Marble Runs And Experiment With Gravity; Magnetism; And Kinetics To Propel Your Marble To The Finish. With A Variety Of Tiles; Levels; Tracks And Elements; You Can Control The Speed Of The Marble. The Open-Play Concept Offers Endless Possibilities To Design A Different Track Every Time You Play. Add Flair And Speed To Your Tracks With Expansion Sets And Action Accessories. Experience The Power Of Gravity With This Epic Marble Run Toy.The Building Expansion Offers Over 25 Additional Elements To Expand Your Track Vertically. You’Ll Increase The Action When Increasing The Height Of Your Run. Experiment With The Combination Of Height Tiles; Base Plates; Freefalls; Switches And Even Another Level. See How High You Can Build Your Track Before Getting The Marbles To The Finish.This Open-Ended; Screen-Free Stem Toy Makes The Perfect Activity For Boys And Girls Ages 8 And Up.