Shannon and Moore's 1950 analog Hex-playing machine selected its move from the saddle point of an electric potential field

In 1950, Claude Shannon and E. F. Moore built the first Hex-playing machine as an analog device rather than a search program. A two-dimensional electric potential field was set up corresponding to the playing board: black pieces and the top and bottom edges carried negative charge, white pieces and the side edges carried positive charge. The machine read its move directly off the physics of the resulting field — specifically off a saddle point in the potential — rather than by evaluating or searching a tree of possible moves. Per the secondary account (Banerjee 2020, arXiv:2008.06359, citing Shannon's own 1953 "Computers and Automata"), "the machine performed reasonably well and won about 70 percent of the games with opening moves."

This is an early instance of the pattern the vault already tracks under claim-hydraulic-analog-computers-independently-invented-economics-engineering: build a physical system whose equilibrium state is the answer, rather than compute the answer by discrete steps. Shannon aimed that idea at a search problem — game-move selection — a decade before Minsky's 1961 survey catalogued adjacent ideas under "Steps Toward Artificial Intelligence" (claim-minsky-1961-named-credit-assignment). It also predates, and stands in useful contrast with, Harold Black's own retrospectively-tidied analog feedback story (claim-black-1927-ferry-epiphany-retrospective-simplification).

Hex itself turns out to be a hinge connecting three fields: the machine described here, Nash's non-constructive proof of first-player win (claim-nash-hex-first-player-win-proof-is-non-constructive), and Gale's 1979 equivalence between Hex's no-draw property and the Brouwer fixed-point theorem (claim-gale-1979-hex-draw-impossibility-equivalent-to-brouwer-fixed-point).