This is pretty solid, and when you compare this to stuff like Ice or Burn the Earth it's clear this is several giant leaps ahead of the kind of stuff you've done before.
The menu, UI, and general vector graphic style all look immaculate. The physics are weird but it's interesting that each level has its own gimmick to keep things interesting. No one would ever know pixel art was your strong suit from looking at this.
The music isn't bad, but it really doesn't fit for a rhythm game. Your looping synths are working against you here; they work great when the game isn't centered around the music itself, but when the dynamics of the song determine the action in-game, more progression and complexity are going to be what give the game its complexity as well.
Obviously there are going to be sacrifices made with the deadline of a Game Jam breathing down your neck but there are a couple things I think would have been easy enough to implement without being too difficult.
The objects on screen should have different colors. This would be the easiest way to tell them apart while playing and really doesn't take more than about 30 seconds of work to change. Sound effects could also be a nice touch (with the option to toggle on and off.) The songs are a bit too long, and especially for easier songs it can be kind of boring to sit through them. Not having a fail state and not being able to see the score during a song takes any sense of tension away. Last, this is a simple enough game that you totally could have added a joystick or some other way to control the game on mobile.
Last note about the general design is that shorter, harder songs (and a fail state) would provide greater encouragement for the player to redo levels and try to perform better.