The rules of the minesweeper game are explained there: http://en.wikipedia.org/wiki/Minesweeper_(video_game).
This repository contains a ruby gem that defines the core concepts of a 2D minesweeper game: minefield, cells, mines and the user interactions with the minefield (reveal, flag, unflag).
Therefore, this gem is not a playable version of the game but if you want to try it, I also built a terminal frontend which uses it.
spec.add_runtime_dependencty "minesweeper-core", "~> 2.0.0"
An example of the usage of this library can be found in my terminal based implementation of this game: svarlet/minesweeper-console.