Uploaded a patch. The only change is on page 91 - due to the late game mechanics, especially those introduced in the section that is hidden behind the key, puzzles 70 and 71 could not have a unique solution without the addition of the showcased output on page 91. I knew about this mistake for a few weeks now, but 99,99% of players would never even realise alternate solutions were possible here, so I took my time with it. Sadly, this change is not yet seen in the physical book but will be if I make a new printrun in the future.