Thank you A LOT for your feedback :) I really glad you enjoyed the game, it made my day. As for the issues you mentioned:
1) true, I was thinking of adding an icon above/below the "eye" crosshair for the first stage, or at least for first 2-3 recharges so that player will get what he should do quicker, but your suggestion with louder recharge sound and maybe some more distinctive visual sign is good
2) yeah, the Rhythm Mode was as this game was originally planned and it ran well while testing on local machine, but then I run into problems with running it without lagging on browsers, and as this is mainly a browser game, I changed main gameplay and put Rhythm Mode as a bonus at end. Yeah, syncing rhythm timer with AudioPlayer would probably reduce the drift, though even if it reduces lagging it probably won't fix it completley, especially on mobile devices
Again, thank you for your time and feedback, if I update game in future I will try to address them, but probably won't update the game any time soon, as I have other priorities currently :)
And great score!