Each domino is a rigid box that pivots about its front-bottom edge. With moment of inertia I = m(h^2+t^2)/3 about that edge, gravity gives I a = m g (h sin th - t cos th)/2 - c w. A domino is only unstable once tilted past th = atan(t/h), which is why a small nudge is not enough.

The top front corner sweeps x = h sin th, so it reaches the next domino's back face when sin th_c = gap/h (the gap must be smaller than h or the chain stops). Contact is an inelastic impulse along the face normal with restitution e, solved from the angular momentum of both bodies.

Simplifications: one hinge degree of freedom per domino, friction folded into one damping term, a fallen domino may pass through its neighbour instead of resting on it, and the path map ignores lateral coupling in curves. The live 3D maze uses the same hinge idea.