This animation, unlike the previous one, includes length contraction along the direction of motion. Now the light pulse has less distance to travel and can keep up with the vertical light pulse. This allows the light pulse in the horizontal clock to cover the round trip in the same time as that in the vertical clock.

This animation also shows "relativity of simultaneity": spatially separated events that are simultaneous for one observer are not simultaneous for a relatively moving observer.

For clocks at rest the reflections from the far mirrors are simultaneous. But for the moving clocks the animation shows they are not simultaneous. This is because spatially separated events cannot be directly compared due to the limitation on the speed of information transfer over distance by the speed of light. This is unlike events that are close together, like the light pulses' arrival at the bottoms of the clocks.

This animation, and the previous, are to scale. The speed of the clocks is half the speed of light. This gives time dilation and length contraction factors of the square root of 3/4, or about 0.866c.