Thank you for the great feedback, and thank you for playing! You make a lot of good points in your criticism.
I handled the sound effects, and I was quite aware of the annoying increase in volume when there's a lot of birds in a level. I definitely need to look into how other games handle many similar sound effects like that before the next jam, because this has been a consistent problem I've faced.
I was a bit worried about mapping E and R the way I did, sorry that it gave you trouble :(. I actually did most of my playtesting with shift rather than E, but I should've thought more about it or even just put the restart button on the pause screen.
I agree 100% that this type of game warrants having an undo button, I'm sure it would ease at least some of the frustrations for players.
-Aquarmity