Medals sometimes don't work or sometimes all medals stop working altogether, requiring you to have to reload the page and re-do everything if you want those medals.
Also there are certain enemies who move too fast such that it's not possible to get through without taking damage. Is this intended or is this a bug? For example one of those red things that moves up and down, you position yourself perfectly to the left of it (but not touching) and the instant it begins to rise you are rushing under it, but it comes down and hits you before you've even made it through because of how slow your player is compared to the enemy. With most enemies this isn't the case but with some it is.