2D Spiral Domino Chain Reaction: Expanding-Path Toppling Physics

Most domino simulators keep the gap between pieces constant. This one lays dominoes along a self-generated spiral whose radius keeps growing as it winds outward, so the physical gap between neighbours is never the same twice — it widens the farther the chain reaction travels. Each domino is still modeled as a rigid rod pivoting about its base under the standard falling-rod torque equation α = (3g)/(2H)·sinθ, and it only knocks over its neighbour once its own top edge, reaching forward a horizontal distance H·sinθ, physically closes that neighbour's local gap. Turn up the spiral's turn count or dial down the domino count and the outer coils stretch until the gap exceeds the domino's own height, stalling the reaction partway through exactly where the geometry — not a manual spacing slider — makes it impossible for sinθ to reach far enough. An auto-trigger-and-loop mode fires the first domino a few seconds after every reset and restarts automatically once the spiral has settled, so you can watch the same equation play out differently every time the turns, count or domino height changes.