Great work! I really like the Witness approach of letting the player figure out the rules from examples instead of telling them explicitly how it works.
That said, the third area didn’t work very well for me. I needed a hint from Discord to figure out how the plus signs worked, even though I had already solved about 10 puzzles. It didn’t help that a lot of the examples either already had a unique solution when ignoring the pluses, or admitted several solutions that seemed very different. The mechanic itself is really cool though, so if you rework the puzzles that try to teach it, this has a lot of potential.
I’ve also got some feedback on the second area, but spoilers, so I’ll message you on Discord. :)