Last week, I had a crash while playing Slay the Spire, the sort where you need to hard boot. I called it a night. Playing the next day, my save file was gone. Wow, ugly crash. Google led me to forums led me to where save files are kept. Okay, the backup save was gone too, and I probably just overwrote the cloud save with a newly created save file when I started the game. And it looked like I only lost the save file for the Ironclad, which would normally gate access to everything else but the other save files were there once I did whatever for re-unlocks on the Ironclad.
This led to the discovery that the save files are plain text. Well, that makes recovery really easy when I can just copy the text from one file to another. My statistics are broken, but then they were broken when I lost the first file. That is also a handy thing if you want to see later Ascensions or something; just edit yourself to Ascension 15 and now they are all unlocked. I have yet to exit mid-run and see if that opens interesting opportunities, but the leaderboards suggest that people have already found plenty of ways to cheat.