The website does say that it was ‘vibe coded’[0] so perhaps the author didn’t test it very thoroughly? They apparently do ‘vibe coding’ courses so.. that’s something.
I tried it various pens and paper sizes and printer scales. And it suddenly worked but only if scanned at low res (200DPI).
Still I got a partially working font at the end
What I do is free and intended to be workshops for non-technical users to understand the power of technology rather than slamming it in their face.