Pretty fun game! And I say that as a fan of The Witness. :)
Here are some thoughts...
I found the twist puzzles to be a lot easier than the knot puzzles as you pretty much just follow the walls - axis-aligned or diagonal. The knots required more thinking.
I think the game is somewhat lacking a-ha moments as the later levels seem to increase difficulty simply by being longer and more tedious instead of introducing new interesting situations. This is just a small complaint though! Just something to keep in mind when making more levels.
The mouse controls could use some work as it's sometimes difficult to get the line where I want. It's also kinda hard to see what knot and twists are left to do if the line is going through the tiles with pink structures once. Maybe the line should be thinner?
Anyway, good work on the game so far!