I remember when I was six, my dad programmed a chess game on the Sinclar ZX81. He used to play real-life chess a lot so naturally, this was his first use for this little box. It was slow as hell and he had to pause screen rendering to make it faster. If you call simple backtracking "AI" then I think my dad wrote that "greatest program ever" too without knowing David Horne. (And my dad is definitely no urban myth, either...)