dude it's so nice to get a comment like this, really, you did right in the points.
my plan was hav a lot of diferent types of enemies, like the subterrain ones. but I'm learning along these projects and as I advance (and learn more) I see how much the beginning was made on a bad foundation and I end up wanting to redo everything from scratch.
the subterrain monster was the first thing which went wrong and ended up discouraging me a lot. I intended to make flying, sea and especially boss monsters.
the idea was for the player to face a few worlds (with increasing difficulty, as you suggested, first one totem, then two and finally three) and then a boss before moving on to another world, with another totem style and other creatures.
actually in this prototype there are only TWO different levels, they change because several elements are generated procedurally depending on the world you are in. but there really wasn't a lot.
in the end I think I spent a lot of time on the visual (as usual) before the structure was well put together. the combat is better than my previous games, but it's still far from what I wanted. kinda clumsy.
but yeah, really happy that you liked and with the feedback. it really gives energy to think more about this project or the next ones. thank you!