It may be nostalgia speaking here, but I really enjoyed the Marble drop recreation with alchemy theme. Obviously, graphics and sound design could be better, but it's impressive for the limited time there was for the Game jam.
Thanks for giving me a way to enjoy this wonderful game from my early childhood once more, but with its own mechanics.
(A small thing you could try for the sound effect of the element Marbles dropping in is: import them as mono and use an AudioStreamPlayer2D positioned at the dropping points, so you can hear them dropping in from left to right)
Overall, I didn't notice any bugs (besides the reset button on level 2 which you already know) while playing, and I like that you added a small sound effect playing for reference when changing the SFX slider.