I should have read the instructions first. Eventually, I did read them and was able to complete the game. The following is not a complaint about the game, just an experience I had not reading instructions.
I didn't know about the left-click attack, so at the first boss, I managed to get him to follow me to an opening in the area, I pushed him through. He disappeared. I thought he was dead, nope, he popped back up like an Evil Dead deadite. I dropped him again, he's gone. I think, OK, maybe I had to get him twice, nope he popped back up! At some point I read the instructions.
My only suggestion would be to allow more time to see the after-boss images. I think I saw the first two for less than a second each.