About 3 years ago I participated in a challenge amongst friends to make the hardest puzzle possible according to the following rules:
it has to have a clue layout with rotational or reflectional symmetry (but not necessarily symmetric logic)
it has to be made by hand, the only allowed computer assistance is software that checks solution count
it has to be minimal
The winner was whoever made the puzzle with the highest SER (computer rating). I ended up winning that competition with an 11.2 puzzle, but we later found out that the puzzle I made already existed and I just wasn't aware of it. Years passed and I was randomly reminded of this event and my undeserved victory, so about a month ago I tried the challenge again. This is the result! Each row, column, and 3x3 box must contain the digits 1 through 9 Solve on F-Puzzles
The link is to the puzzle in #196 which I enjoyed very much