Cool idea! A visualisation of the trajectory might be a nice touch - maybe hold to see trajectory and release to jump?
Changing direction is a good concept but doesn't really seem to have any impact on the game, most of the time I couldn't even tell if I'd done it correctly. Expanding on this concept more might open up more meaningful decisions for the player.
Loved the black holes, they were pretty satisfying to watch collapse. There's a really annoying tail on the coin collecting SFX - if you're using BFXR try changing the high pass filter or otherwise just open the sound in audacity and trim the end off.
Pretty fun game, congrats on finishing it!