Every now and again you come across something that stretches your brain in a new direction. Last week I stumbled on a magic trick of a Choose Your Own Adventure: Al Leonardi’s Ace of Aces, a paper computer running a first-person shooter, programmed in 1980—eleven years before Wolfenstein 3D, the “first” first-person shooter.

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Choose Your Own Adventures are essentially a look-up table: after each page the player is presented with a list of options and the page to turn to if you choose that option—a look-up table that converts their choice into the next page number.

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First: what is Ace of Aces? It’s a two-player World War One dogfighting game. One of you is the Red Baron, one of you is Snoopy Biggles, and you attempt to line the other up in your sights for some dakka dakka dakka. So far so several other board games. What sets Ace of Aces apart is the ingenious interface: you play with a pair of picture books, one for the German pilot, one for the Allied pilot. Each page of the book shows you the view of your enemy given your current position.

Each page has a list of manoeuvres you can choose from and the page to turn to that “performs” the manoeuvre. I’ve put “performs” in quotes, but as we’ll see, the look-up table actually has this maths encoded into the page numbers, it’s some sneaky-clever design.