Thanks for your kind comments.
As indicated on the page of the game, I shut down the audio for the web version. If you want the audio you need to download a desktop version (or look at the full playthrough on youtube).
Regarding the bonuses, did you get that you need to catch a power up and then use ctrl on your keyboard to validate this bonus? If so, please let me know as I would be interested to know if there is something not correct on some browsers.
Regarding the bosses, their bullets disappear when you beat them. I am assuming that you beat the first mid-boss (and indeed, mid-bosses bullets do not disappear).