Pump the marble in rhythm (SPACE at the bottom, where it's fastest) so each kick adds energy — resonance — until it crests the low right lip and slingshots out. But a body has length, and the well is steepest at the lip: cross too fast and the tide across it (head pulled harder than feet) tears it apart. So pump enough to clear the lip — and ease off before it, so you crest gently. Resonance is the only safe way up. The danger is the handle.