At first sight, this is remarkably more accurate that the "slower speed of light" game from MIT that was made available all those years ago (~2012).

Many issues with the MIT game were discussed here:

https://physics.stackexchange.com/questions/43695/how-realis...

While the thread lists multiple issues, the issue that I found was with modeling temporal aspects of relativistic doppler (I also reported it on the github repo of the "slower speed of light" project, but that doesn't appear to be maintained):

https://github.com/MITGameLab/OpenRelativity/issues/17

In this game, it looks like the temporal component of the Doppler effect is modelled correctly.