So, I just finished playing through the trilogy in a "hand holding" playthrough where I read all the hint prompts (which I'll make a separate post about, did notice some interesting things). Basically, what I would do is idle until I get the hint prompt, ONLY do what it says, and then as soon as the hint prompt disappeared I would IMMEDIATELY stop what I was doing and wait for the next hint before doing anything else - even if it seemed like I wasn't done (which sometimes was the case).

Anyway, that aside - the puzzle in the penultimate level in the three-book room, with the 4x4 grid of buttons and the castle model (which starts as a path model, and then a sudoku).

The hint prompts for it seemed to imply that the Occulus was supposed to show me "arrows" on the button-grid device indicating the start and end. Yes, there was an Occulus clue on the castle model so at first I thought it could be a mistake - but then it was mentioned again in the next clue!

Now, I know there's arrows on the box design itself which serve the purpose described, but I'm curious if they were original invisible Occulus marks rather than physical box fixtures?