Yeah, that totally makes sense! And I completely agree with you. I loved your tutorial and how you explained things to the player. I wouldn't change that at all. For me personally, I got that the trident blocks because you had one human be both blocked by a trident and launched into the lava with the other trident. If you wanted another example of the trident blocking humans, one thing you could do is place the humans at the bottom where they would normally fall and then split that little section down the middle with a trident to block humans from going the entire span (I hope the description makes sense lol). But I am just some random dude on the internet and this is personal preference, so take what I say with a grain of salt. What you produced here is incredible and I am very impressed with it. Really well done.
As for music, I did hear music on the credit screen at the end, but not during game play. During game play I just heard the ambient sounds/static, which was a great touch.
I just went back and re-played it. After I got through the levels and past the credit screen I went back to the main menu and the music continued. Maybe it's something to do with the browser that is causing that.