I was so excited about Perplex City when it came out in 2005.
I ordered cards and set about solving the puzzles on the cards. The big idea was that real life mixed into the puzzles a bit (“alternate reality game”) in a search for “a priceless scientific and spiritual artifact” known as The Cube. It was found a few years later.
I never got that far into it. But I did solve some cards, and at one point I even sent some of them in and received back some kind of prize. The details are fuzzy now on how that all went down. I tend to save physical artifacts from fun things like this in my life, so last night I got out the ladder and got down my box of stuff like this and rooted through it. I was almost sure I saved my Perplex City stuff, but I couldn’t find anything. Epic sad trombone.
Anyway, I was thinking of it, because I just read that the last Silver card was solved. The card difficulties went Red, Orange, Yellow, Green, Blue, Purple, Black, and Silver. One of of the last Silvers is to solve The Riemann Hypothesis, which is not done (and wasn’t designed with a solution in mind). Other than that, the last one was to Find Satoshi.
This video was before it was found:
And it was finally done.