A flip puzzle
Top Spin was a puzzle in which 20 beads were placed on an oval track with a turntable, such that any four consecutive beads could be flipped. Naturally, I wondered whether it was possible to reverse the order of the beads, from [0, 1, ..., 19] to [19, 18, ..., 0].
As it turns out, this is possible even if the beads are placed on a straight track instead of an oval one.