That's an excellent walkthrough - speaking on behalf of the Arberth team, we particularly like how Malcolm has dealt with the 'why' as well as the 'what', by so meticulously pointing out the clues as well as the solutions to the puzzles.
I believe my partner Karen has separately pointed out the walkthrough's slight error with the books in Rhiannon's room.
Malcolm has also given me a bit of work to do - he has pointed out what may be a bug in the Air chapter. I've noticed some struggle with this while others seem not affected and it didn't come up in the testing - but now I'm prompted to look into it in a bit more depth. If it does turn out to be a bug, I'll look into issuing a patch.
Well done Malcolm, on many counts.
Best,
Noel Bruton
Arberth Studios