Palaeontologists read speed straight from stone. R. McNeill Alexander noticed that walking and running animals of every size obey one rule — if you measure them the right way.
The trick is the Froude number: speed squared, divided by gravity times leg length. It strips out body size, so a chicken and a sauropod land on the same scale. Below about 0.5 an animal is walking; past 1.0 it must be running, because a stiff-legged vault would fling the foot off the ground.
From a trackway you measure two things: the stride length between successive prints of one foot, and the hip height (roughly four times the footprint length). Alexander's equation turns them into a speed.
That is why relative stride — stride divided by leg length — decides gait, and why giants taking enormous steps were usually just strolling.
Something in the simulation stopped unexpectedly — the lesson continues without it. Nothing you did was wrong; you can move on.