Stand them up, tip the first one, and get out of the way.
Nothing has fallen over yet.
A domino can knock over one about half again its own size. That is the well-known figure, and it is why the growing chain is worth trying: the energy is not coming from your push, it is coming out of every tile that was standing up, one after another. All the first flick had to do was be enough for the smallest one.
This table cannot manage a half, and the set piece says what it can. Tried rather than assumed: the growing chain carried all fourteen tiles on every run at 1.10 times per tile, stopped at twelve every time at 1.14, and died at the second tile at 1.22. So it is built at 1.10. The shortfall is the simulation’s and not the world’s — these tiles are perfectly rigid and meet at a single point with almost no bounce, where a real domino gives a little, grips, and spreads the blow across a face. Spacing turned out to matter as much as the ratio: 0.40 of the pushing tile’s height carried the run, and 0.32 and 0.46 both broke it.
Everything here is rigid-body physics: real rectangles with real friction, standing on a real floor, falling into each other. Nothing is choreographed, so a run can fail exactly the way a real one does — too far apart and the chain dies; too close and a tile lands on top of its neighbour instead of pushing it; too big a jump in size and the little one bounces off.
Drag across the felt to lay a whole run at the spacing you have chosen. Everything you build stays put until you sweep the table.