a guessing game called Mastermind, and the AI to solve it.
https://en.wikipedia.org/wiki/Mastermind_(board_game)
an online game is here: https://www.webgamesonline.com/mastermind/index.php
a decoding board, with a shield at one end covering a row of four large holes, and twelve (or ten, or eight, or six) additional rows containing four large holes next to a set of four small holes; code pegs of six different colors (or more; see Variations below), with round heads, which will be placed in the large holes on the board; and key pegs, some colored black, some white, which are flat-headed and smaller than the code pegs; they will be placed in the small holes on the board.