Hi Brian. The explanation is great, crystal clear, but unfortunately both the animation and the diagram are completely wrong. The light particle velocity should be c in both directions but, in both visualizations of the horizontal light clock, the speed is being added in the newtonian way. The board diagram is specially wrong beacuse after the reflexion on the right mirror the light particle is still going to the right at less speed. It should be travel to the left at speed c! Although the reasoning is impecable of course, the diagram is wrong and confusing. You should correct it.

Two way time dilation clocks equation- L/(gamma*(c-v)) + L/(gamma*(c+v)) = [L(c+v) + L(c-v)]/(gamma*(c-v)*(c+v)) = 2Lc/(gamma*(c^2 - v^2)) = 2Lc^2/(gamma*c*(c^2 - v^2))

tysm