many implementations of one interface... @board[x, y]

gistfile1.txt

class Board
  def [](row, col)
    @grid[[row, col]]
  end
  
  private
  
  def default_grid
    {}
  end
end

gistfile2.txt

class Board
  def [](row, col)
    @grid[row][col]
  end
  
  private
  
  def default_grid
    Array.new(10){ Array.new(10) }
  end
end

gistfile3.txt

class Board
  def [](row, col)
    i = (row * 10) + col # so it's just a single array stacked   123456789012345678901234567890
    @grid[i]
  end
  
  private
  
  def default_grid
    Array.new
  end
end

gistfile4.txt

class Board
  def grid(*atts)
    @grid[atts]
  end
  
  def default_grid
    Hash.new
  end
end

gistfile5.txt

# and once you get really fancy and you want to host this game on 10 servers using round-robin

class Board
  attr_accessor :id
  
  def key_for( x, y )
    "spot_#{id}_#{x}_#{y}"
  end
  
  def grid(x,y)
    lookup_in_memcache( key_for( x, y ) )
  end
end