With your cursor inside the minesweeper window type "XYZZY" then press Shift-Enter and Enter. A white dot should appear in the upper-left corner of the screen. If it turns black, your cursor is resting on a mine.

Mine's was started by Tsuzo Niikura in 1985. It attracted attention in 1988 by being among the first Japanese companies to sell re-programmed ECU systems for popular Japanese sports cars.