Earlier today when I saw this thread I came to post my game that "should have won but didn't", only to see to many other people posting the same. For me it was the "no duplicate columns or rows" rule that I didn't notice. Something about this game is tripping a lot of people up.
The thing is I know about the rule of equal number in each row and column, and have used it to solve a few 10x10, but when switching to a 4x4 I forgot it exists. I took some time and went trough the rules I knew, before posting this "error", but that one rule was gone.
