Bacon's Cipher
en.wikipedia.org
en.wikipedia.org
E.g. in letter "W", in most fonts the the middle part touches the top (So: "..."). But in monospace fonts, like the one used in HN's comment reply text area, the middle part is lower (So: ".."?). And in wikipedia's logo the "W" is stylised as overlapping VVs (So: "...."??).
I've been dying to watch it again since I was 10 years old or so but it's such a niche series that I don't think it has had any later distribution in the digital era.
The Wikipedia article was unsatisfying so I googled to learn a bit more.
In that adventure I learned basic algorithms for decrypting substitute ciphers which in turn has led me down another rabbit hole.
Great stuff, thank you!