Thanks for the detailed feedback and valuable suggestions!
I have implemented suggestion #1 (crouch/dropping eggs behavior), and allowed gamepad button 2 to jump/fly as well (improves the experience on D-pads).
I'll try to apply some of the other suggestions on time for the deadline of the Game Jam, but I also want to keep game.zip small enough to be eligible in the JS13K category.
In any case, I certainly intend to keep on developing the ideas after the Game Jam ends. I really like Little JS's lightweight design, in comparison with other JS frameworks (e.g. Phaser) which sometimes feel a little bloated and difficult to debug.