Created: 2012-03-24 09:47
Updated: 2014-05-15 14:58



The game

Long version: see Wikipedia

Each turn, you can either reveal a location or flag it:

Reveal a location.

  • This will show the number of mines adjacent to that square (including diagonals).
  • If that number is zero, it will also reveal the full extent of the safe zone.
  • If the location contains a mine, you lose.

Flag a location.

  • This will mark a location as containing a mine (or suspected of containing a mine). It has no game effect other than as an aid to the player.

You win if you can successfully locate all of the mines - that is, reveal every location that doesn't contain one.

Additional rules

  • The official interpreter is Ruby 1.9.2.
  • The player will not have access to the game objects.
  • The player may require Ruby source files from within a lib directory in the same place as the player file (i.e. players/player.rb can use players/lib/foo/bar.rb via require "foo/bar".)
  • A file should not implement more than one player class.


This implementation is based on the ruby implementation for the game Battleships, as found here

Play takes place on a square grid (defaulting to 10x10), with a certain number of squares containing mines (default is 10). Co-ordinates are given in the order (x,y) and are zero-indexed relative to the top left, i.e. (0,0) is the top left, (9,0) is the top right, and (9,9) is the bottom right.

A player is implemented as a Ruby class. The name of the class must be unique and end with Player. It must implement the following instance methods:


This must return an ASCII string containing the name of the team or player.


state is a representation of the known state of the board, as modified by the player’s shots. It is given as an array of arrays; the inner arrays represent horizontal rows. Each cell may be in one of the following states: :unknown, :flag, :mine or the number of adjacent mines. As flags are markers that you set yourself, and revealing a mine will end the game, a typical board will contain only :unknown and numbers. E.g.

[[1,    2,    :unknown, ...],   [2,    :unknown, :unknown, ...], ...]
# 0,0   1,0    2,0              0,1       1,1       2,1

take_turn must return an array of co-ordinates for the next shot, with an optional third element containing true of false, with false depicting a flag notation rather than revealing the square. In the example above, we can see that the player has already played [0,0], [1,0] and [0,1]. They can now be certain that [2,2] is a mine, so they return [2,2,true] for their next shot.

The console runner

A console runner is provided. It can be started using:

ruby bin/play.rb path/to/player.rb

Players are isolated using DRb.

A couple of very basic players are supplied: StupidPlayer guesses at random. Human Player asks for input via the console.

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