In order to relax I am writing a document called All The Words I Know (In The Order I Think Of Them), in which I try to list every word I know . . . It gets harder and harder as you go on of course and realize that you've already used lots of words. I realize this may be a strange way to unwind but people do sudoku and stuff and this doesn't feel much different to me . . . . it gets harder and harder to find ones you haven't used . . . . i bet one could write a simple program that would turn duplicates red or something if one knew how to do such things.
Your mission, should you choose to accept it, is to create such a simple program. I think a simple webpage with javascript would do it.
Relevant Technology Plain vanilla HTML+ javascript would probably be fine, but libraries might make it prettier. Someone ambitious could make it fancy with accounts, saving your file, a leaderboard, and suchlike.
Complexity