Thanks for reporting! It's not about the save data actually (which takes only a few bytes), it's about the build itself which is around 50 MB due to the size of the music files. I'm afraid there's nothing I can do about it since it depends on the user's local configurations, which in most cases allow for plenty more. But you can easily work around the issue by downloading the demo, which will provide a better experience anyway (better performance, better music quality, etc). Have fun!