Managed to fix it: had to install a 32-bit JRE on my 64-bit system, then set the JAVA_HOME environment variable to C:\Program Files (x86)\Java\jre-1.8\bin. Wasted all this time troubleshooting so I could play a poorly designed game that further wastes my time every time I restart a level.
This game would make sense if you were controlling a rocket or something, but instead it’s a magically rotating lifeless spacesuit with a lopsided light source whose only purpose is to mislead the player even more than the bizarre angle of the body. Not worth the price. Shouldn’t be charging any amount of money for this in the garbage state it’s in, honestly; and the dev seems to have been inactive for four years, so that doesn’t seem likely to change.