Okay, just found out that... @data[x][y] unless y<0 or y>@height ...is the same as stating nil anyway, according to http://www.themomorohoax.com/2009/05/21/when-to-use-nil-in-ruby-methods The error I'm getting is... undefined method `[]=' for nil:NilClass (NoMethodError) ...when the program hits this part of the code... Array2D[x,y,1] = "X " -- Posted via http://www.ruby-forum.com/.