can anyone tell me if this has been done before, or if I can claim credit?
I'd be surprised if I was the first to come up with this though - it's a fairly basic idea. I call it 'algebraic sudoku' because instead of given numbers, the 'clues' are algebraic relations between various squares:sudokuguyblog.blogspot.com/search/label/algebraic%20sudoku { link corrected by Moderator }
my inspiation came from the famous Foxtrot cartoon. this was a fun puzzle to make and I'll be sure to do some more of these!