Minesweeper, the game Microsoft bundled with Windows, ported to the TS2068 in C with Z88DK by Alvin Albrecht. The board, the flags, the numbers, the regrettable first click are all present.
Albrecht wanted one the computer could play well, and play fairly, deciding every move from the numbers on the board and never from the mines hidden below them. Each revealed number becomes a Boolean statement of the mine arrangements it permits. As the board opens, the program combines these statements, discards the combinations that contradict each other, and surfaces the squares that are certain; a guaranteed mine, or a guaranteed safe step. When nothing is certain, it computes the odds for each square and takes the least dangerous one.
The Boolean work runs on ROBDDs, reduced ordered binary decision diagrams, which is a great deal of formal-methods apparatus to find inside a Z80 game, and possibly the first time anyone put it there.
