Really enjoyed my time with this, but there's a few bugs. First, it doesn't seem to be possible to collect all 20 chests, as at least the two chests in "Home?" are bugged and don't stay open/aren't added to the counter. There may be another like this as well as a few players on the steam forums for the game seem to be stuck at 17/20.
Second, some flags seem to stay set even on starting a new game. For example when entering the area with the falling bridge on a new save, I'm teleported to outside the little house as if I just cleared the "boss fight" in there and can't go in there to fight him on that playthrough.