Congrats on your first game jam, sir!
For the volume slider you need to use db_to_linear(AudioServer.get_bus_volume_db(bus_index)), otherwise the sound is going to go from one extreme to the other one when moving the volume slider.
I've enjoyed the game, I like your implementation of the momentum theme.
Level design could use just a little bit of more work, as it can get frustrating in some parts.
But bonus points for the settings menu and the different levels adjusted for different difficulties!
But thank you for this game and KEEP MAKING GAMES, sir!