This was fun. I found that shooting enemies wasn't too beneficial until the big boss, so basically I just SCOOTED through every level until him. Then I lit that box up like 100 times. I was clicking so rapidly that when I beat him, I think I clicked past a screen. I saw it flash then bam, back to stage 1.
I know you said that the movies weren't working on the browser though. (happened to me with a game jam last year. something about browsers and permissions for .webm/mp4. I know your pain)