Save files are stored here:
Windows: %APPDATA%\Godot\app_userdata\KittyToy
Linux: ~/.local/share/godot/app_userdata/KittyToy
macOS: ~/Library/Application Support/Godot/app_userdata/KittyToy
find the file “kittytoy_save.save” and copy it somewhere safe, and if you ever run into a broken or lost save file again, you can just copy it back ^^