This is a minimalist, focused, puzzle-solving experience. While I preferred the puzzles that introduced more novel elements, I can also respect Alan Hazelden and Harry Lee's drive to iterate heavily on a small range of elements. That ramped up the difficulty quite a bit, in my experience. That sometimes led to frustration, usually for later puzzles in which it seemed that I had to figure out the best opening and full sequence for a solution. I liked the puzzles that more obviously allowed for multiple paths to a solution better - despite being easier, I had a greater sense of accomplishment in solving them and less of a sense of trial and error. Even so, these puzzles kept me coming back, bit by bit, sometimes with months in between.