I found this frustrating and hard, which I think was the point, so well done. My only real gripe is that some of the level transitions in the post-checkpoint section felt unfair. There were a couple places where you enter a door and immediately get whipped into the wall by the wind, and now you have to start over. The combination of that + sparse checkpoints made this hard to play, but other than that this was well-crafted and I enjoyed it! And I think the pre-checkpoint section is quite fair and fun on its own. Here's my playthrough.