
The two that are my own fault are a silly transposition in Classic 5, and entering the answer code for the wrong puzzle into the Tic-Tac-Toe winner answer box.
The one that annoyed me was subtly changing the layout of Hashtag Sudoku. When it has appeared before (on a past Chinese round, I think), and also in the example puzzle, the lines have gradient 2 (or one half). I happen to know I'm not great with that layout, so during the contest I simply skipped that page of puzzles. Solving after time, I realised that they'd changed the lines to have gradient 3 (or one third) which made the puzzle essentially trivial if you realised that gave you repeating groups of three digits within several rows and columns. It took me less than 3 minutes, for 50 points that I totally ignored during the contest...
So am I justified in feeling slightly annoyed that the puzzle in the contest was different from past Hashtag Sudokus, and in particular, different from the one in the example booklet? There's not exactly a huge body of past puzzles to compare it to, but I still would have liked for a different name to have been used for this puzzle.
I really enjoyed the Kropki puzzle, though, and I think limiting the Kropki rules only to the lines was a brilliant idea that allows for much more creativity and flexibility in the puzzle type. I won't be surprised if we see more of those in the future.