It is testing is the theory
that there's a percentage of 40-something men who played it so much that it's just permanently there. The map-making probably reinforced it.
See also:
www.thedailymash.co.uk/news/arts-entertainment/man-still-knows-where-all-the-rooms-are-in-jet-set-willy-20180418147489
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monkeon schmonkeon, Fri 12 Nov 2021, 14:45,
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