ruby.rb

        @matrix = [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
                   [0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
 
        
## with the below code, only the first zero in the whole matrix is changed

        @matrix[0][0] = 1
        p @matrix
        
        
## the below code resets the matrix, but in a purely implicit way which allows the matrix's size to be set in just one variable   

        @matrixsize = 10
        
        @blankrow = []
        until @blankrow.length == @matrixsize
            @blankrow << 0
        end
        
        @matrix = []
        until @matrix.length == @matrixsize
            @matrix << @blankrow
        end

## however, this method of resetting the matrix produces a weird result that doesn't make sense when you try to change only the first zero again

        @matrix[0][0] = 1
        p @matrix
        
## please note i tried running this code on https://repl.it which runs ruby 2.2 from 2014-12 and it produces the same result