Thanks for the feedback -- I agree it's really unfun when you're stuck on one type of puzzle, to not have an opportunity to practice it again until solving 5-6 puzzles you already understand.
I'm brainstorming some ways to address this as I stretch this into a bigger game, like having different sections which focus on specific puzzles. I think playing the same exact puzzle over and over is slightly too repetitive, but maybe something having it be about 40% would be OK.