Near the bottom-right corner of a page of code I was reviewing, there was a regular expression application written in two dimensions, with two parallel horizontal lines crossing two parallel vertical lines so that at each intersection, a one-character variable name was shared.

      %        %
      %        %
      r        r
                
  %%r e asdasd f r%%
                
      s        s
      d        d
      f        f
      s        s
      d        d
      f        f

  %%r g asdasd h r%%
                
      r        r
      %        %
      %        %

The two-dimensionality made the relationships between the rows and columns more clear while also deduplicating instances of the variables where the lines crossed. I thought it was very clever.

The overall shape and the top/left %%rs were pretty clear. I don't remember exactly what was in between, if the %%rs were mirrored with r%%s at the bottom and right, or if there was something else there, maybe involving #.