Thank you for going to the trouble to produce the movie, Irv! It was very helpful. It turns out the disappearing window issue is because you are using the macOS 10.6+ Python 3.7.3 installer variant rather than the macOS 10.9+ installer variant. For some reason, the Tk built for 10.6 has this problem but when built for 10.9 it does not. So this problem is, indeed, not the two instances of IDLE behavior I speculated. The fix is simple: don't use the 10.6 variant. In fact, as of the beginning of 2020, we no longer provide the 10.6 variant for any version. I don't have experience with pygame but I did a quick test on 10.15 following the directions on the Pygame Getting Started page and verified that the aliens example worked with the latest 3.7.7 10.9 installer. I also tried with 3.8.3 and saw that the problem there is that the project has not provided a pre-built wheel for Pygame 1.9.6 so the installation fails while trying to build everything from source. I did try their suggestion further down the page to use a pre-release of pygame 2.  The latest prelease, 2.0.0.dev8, does have a prebuilt wheel for 3.8.x on macOS; it installed without issue and the aliens still worked. (Now back to the original issue!)