Split the directions of the marbles with the Gravitrax Pro Vertical Splitter Split the directions of the marbles with the Splitter. See if the marbles have enough speed to roll across the trap door. If they roll too slow the marbles will fall to awaiting tracks below and will go in different directions. Combine this Add on with the GraviTrax Pro Starter Set. This STEM system [Science Technology Engineering and Maths] is an ideal one to teach kids about gravity magnetism kinetic energy and fun. Hit a snag? Freestyle with your own track design or use the tasks and blueprints included to help you to get started in the world of GraviTrax! Are the gravity spheres stopping or flying off before reaching the end target? Time for some problem-solving. Rebuild and try something different! The GraviTrax track system can be extended indefinitely with extra track packs and add-on’s each sold separately.