Thank you for playing, enjoying the game, and the detailed feedback!
I'm surprised that you didn't hear the music because there is some. It's not super loud but it is there.
The problem with the level design or in general with the tutorial is that I don't like written tutorials (like: "you can do this and that and if you do this you can do that with the other item"), there is nothing wrong with them, but I think "show, don't tell" is much nicer. This is what I tried in Level 3. The idea is that you enter the room and above you the first humans get catapulted into the lava which is supposed to teach you about the bouncy tridents. Then when you recall the tridents the blocker is removed and the humans falls down. The idea here was to teach the players that a trident can block and if you forget to block, they will fall down.
It's quite hard to teach such things without constructed not natural situations like this. But I try to redo the tutorials to and make the game easier to understand, maybe I will find a way that feels less punishing. In general it's better to not teach all the stuff in one room so I want to add at least another tutorial room anyway.
Right now I'm doing some experiments with people NOT falling down from cliffs but from small steps, but I'm not sure if I like that. It would make Level 4 much easier but it removes a lot of the chaos which I really like :D