When the spiral twist has its concave side up, marbles will run from the arm into the outer ring and rapidly down to the center. With the convex side up, the flow of marbles is reversed. * TWICE THE SPIRAL FUN: Marbles travel inwards on the concave side of the spiral twist and outwards on the converse side * DEVELOP LOGIC: Inspired by Da Vinci Circles, the German-engineered design makes the marble race construction fun practice for logical and engineering thinking * ENCOURAGE STEAM EDUCATION: The unique marble run system is ¡ãa lot like coding¡À (assessment form the Wall Street Journal). It helps your child develop spatial thinking and an understanding of STEAM principles * COMPATIBLE WITH HAPE QUADRILLA SETS: Get twice the spinning out of your Quadrilla set. Suitable for standalone play or for pairing with other Hape Quadrilla sets * SAFE TO PLAY WITH: Rounded edges, made from wood and compliant with safety and quality standards WARNING: Choking hazard -Small parts. Not for children under 3 yrs.