This gameplay is nicely done! The gravity switching mechanic was brilliantly used throughout each level, and the trial-and-error method of discovering the level, although made linearly, was a fun aspect. However, like all games made for game jams, there is always something that can be polished more, as some others have already pointed out, so I won't repeat it here, but note that even with simple art and music, a good gameplay makes a good game, so good job on you for that.
The interesting thing in my playthrough is that my very first one was slow and calculated, but the following ones were speedruns. After getting to know the simple controls, one can definitely finish these levels as fast as possible. Great and fun game overall!
(Also, another fellow game developer that used the gravity switch mechanic!)