Checkpoints were something we considered early on but didnt really fit the genre we were going for, but instead we kinda designed checkpoints via the level design that once you got past a certain section to a new area like the minecart area you'd be "safe" there. If we had the time though possibly could of looked into having an 'Easy' mode with some form of checkpoint system.
Yeah the flying can take a bit getting used to but once you do its quite rewarding. Though probably some parts we could of tweaked a bit more but didn't want to make it to easy. Im glad though you enjoyed it overall!