Hi! Great to see another one from Simpathey stream, I also saw her playing your game haha. The control mapping of rhythm games that go from right to left can be really tricky. For my personal high score runs I ended up using 'W' and 'Arrow down', so I can use both hands and still have a physical upper and lower position of the buttons, but I though for the default controls that probably wouldn't be a good idea. I chose the mouse buttons because Muse Dash (similar gameplay, also rhythm game that goes from right to left) has the same controls.
Thanks for you suggestion about the bottle position. It might really be worth a try. I am not sure about having all notes on one track though, since then you wouldn't be able to require the player to press both notes at the same time, and it would make the game inaccessible to the color-blind community. But maybe having two tracks, but placing the bottles on top is the best solution? I definitely have to think about that, thanks so much for your feedback and also taking time to include an example image!