Finished it in just over an hour minutes with the gem ending. I really enjoyed it, and kind of want to speedrun it, but I have a few issues which I'll get to after a quick review. For $2 it's totally worth it if you like a really clean short exploration platformer [a few very tricky sections, but most are pretty fair and the checkpoints are generally very forgiving].
1. As someone who frequently uses the map, it's very easy to accidentally fast travel to another area, killing progress, which is really frustrating and happened about 6 times to me throughout the game. I really think the input for fast travel should be changed to avoid this.
2. I finished the game with 769 coins. The last of which are guarded by the teleporting enemies at the bottom of the airship. This is by far the most cruel section in the game, and doesn't feel fair at all. I've tried this section many times now and haven't even found a way to consistently get past the first enemy, let alone the rest. I really think this should be changed significantly. I know you want this area to be challenging, but this is too much. I really want to get the coin ending [I think I found the secret door to get this ending already] but this section is gatekeeping me pretty hard.