Thanks for the very detailed feedback and glad you enjoyed it and played it through to the end, a lot to respond here.
Regarding the movement/firing mechanic - these were primarily chosen because this game is designed to be a mobile game, this also explains why lightning button can be pressed with an alternative finger.
I do like the idea of a progression bar, will be a little tricky because the enemies wait until the last sub wave was destroyed.
Regarding the lack of story and not being a "Chapter", well the easter egg references this - again I switched my efforts to working on mobile games, hope is to release an actual game this year.
Thanks again for playing