スカイレール

My kid spent two hours building a track across the living room and the marbles actually stayed on it the whole way down. The pieces click together tight enough that it doesn't wobble when he bumps it.

The five-yard track span is what sold me, and it actually holds up—we strung it across the whole playroom and the marbles keep their speed the entire way down. Setup took maybe twenty minutes but the payoff is hours of quiet.

My kids figured out the suspension track on their own within ten minutes, and the marbles glide down that whole 5 yards without falling once. It's been set up across the living room for a week now and nobody's asked for the tablet.