The SHENZHEN I/O game on Steam launches after overriding LD_LIBRARY_PATH. Sadly this means it can't then load libGL on NixOS. I had to modify the launcher script under ~/.steam/steam/steamapps/common/SHENZHEN IO/Shenzhen so that it would prepend, instead of override:

export LD_LIBRARY_PATH=$STEAM_LD_LIBRARY_PATH${LD_LIBRARY_PATH:+:}$LD_LIBRARY_PATH

I emailed this to the creator of the game but they indicated that NixOS is not supported and so may not be able to do any work for it.

Do we have any mechanism for patching a Steam game ourselves?