Edit: This is now fixed in version 1.0.4
Weird! That means something must be throwing an exception while loading the game, but it's getting enough into the loading to start rendering the background color. I could get an idea of what went wrong if you press Win+R, paste in %USERPROFILE%\AppData\LocalLow\Nifflas' Games\Xenosphere - the last bunch of lines of Player.log will probably contain information about what happened, the info will probably begin with the word "Exception" but I'm not 100% certain
One thing that might fix it is installing the latest Visual C++ Redistributable from https://learn.microsoft.com/en-us/cpp/windows/latest-supported-vc-redist?view=ms... (the X64 version)