Alexander,
Your video needs to be commended, because it is quite a challenge to present all 3 relativistic effects in less than 9 minutes! The way you do it is quite original, and it is certainly interesting how we can get the time dilation effect simply by considering the vertical motion of the light bubble in the frame of the spacecraft. I have been teaching introductory special relativity to 19-year old students for over 20 years, and I know that what is particularly difficult to explain comes next: the symmetry of time dilation (that makes clock D indicate 1.15 microsecond when it passes clock C reading 1 microsecond), and the de-synchronization of the moving clocks relative to the Earth's frame. As a specialist of relativity, I can follow your demonstration step by step and all is well, but I wonder how the neophyte reacts to your explanation of the "1.15" seconds... and the fact that clock D counter-intuitively starts running before its sister clock B reaches the tower is probably even harder to swallow. However, I don't really know how it could be explained more satisfactorily within the setup of your presentation and the length of your video. :)
I hope your video does well in this contest. Good luck!
Marc
P.S. Thank your for reviewing (and presumably rating) part 1 of my trilogy of videos "This Is Physics". If you have time to view, leave a critique and rate the other two parts (using your author code), it would be quite appreciated! I think many of the participants in the contest have not yet realized that a video needs to get AT LEAST 10 COMMUNITY RATINGS to be considered for the final round, so I have started to actively ask for ratings...