The update apparently read previous save files as corrupt, killing hours of effort that players spent playing the game.
The developers at Polytron have since remarked that they’re on the case:
“We’re trying to find out what happened and fix it as soon as possible. Like, in less than two months.
YAY GAME DEVELOPMENT!”
That was probably sarcastic. It will likely be fixed much sooner than that.
Check the source for the entirety of the patch notes in case you’re interested in seeing what was supposed to happen.