GraviTrax The Game - FlowGraviTrax The Game Flow Put your marble run engineering skills to the ultimate test! In the Flow the ball finds its way through the FlexTube and must handle height differences by adding a small transparent level. The modular, electronic free, interactive track system of GraviTrax becomes a challenging brainteaser as builders think their way through increasingly difficult challenges. How does the ball get from start to finish when, for example, only