Rink Logic: the stone never stops until it hits something

A sliding-stone puzzle on 20 seeded boards. Stones glide until a wall or another stone halts them, so park bumpers to build your own walls and land the red stone on the target. A breadth-first search finds the true minimum; match it for three stars, ask for a hint, or watch the perfect route. Keyboard (arrows or WASD, 1-3, Z, R, H), swipe, tap and on-screen pad.