In an early version of
Codex Bash, one of the puzzles - the one involving paper circuit diagrams - was different.
Recent players will have rummaged through laminated sheets strewn around the room and, I hope, will have tripped over a few before they got to the puzzle where they had to use them. But in the first version of the puzzle these circuit diagrams were all in the one booklet, pictured below. Hardly anyone could solve the puzzle without being told what to do.
I changed the user interface over and over. At one the point where the screen would show a picture of the schematics booklet, and the booklet itself would be in clear view right next to the screen. Yet players would still stare at the screen for ages trying to make sense of it. They would look directly at the booklet and stare back at the screen again, without laying a finger on the booklet itself.
I needed to work out what was going on.