This is an interesting point. In the last 20 minutes I broke 3 puzzles, one of which was Quad max-min. My error came quite late in the solve, and I had 90% of the grid filled before I realised my error. It was quite a big error, and many digits in the grid were wrong, and yet when I solved the puzzle after time I compared the two grids and the digits in A, B, C & D were all correct. If I thought to opportunistically submit the key I did have during the test I'd have ended up with 23 more completely undeserved points.

Classics were my favourite, really beautiful puzzles. Innovations were also clever, but I've always thought real beauty is to be found in simplicity. The irregular was fabulous, only just surpassed by the inequality in my eyes.

(I10) Sum of Them seemed exceptionally tricky. In four careful attempts I always reached a contradiction. Attempt 5 finally solved it.

Many great puzzles. The Innovations are delightful -- I especially liked Coordinates. Inequality seems quite hard (still working on it).

I request the authors to make another test next week.

The INNOVATIVE's were just superb i loved it. I found Classic Inequality tough as i am not getting start. Also i was able to solve 50 % of total sudokus i hope i start increasing that percentage from next test.
To respected author, one fact i would like to share i found it while solving the c4 classic sudoku i got my A,B,C,D with almost 12 cells still left to be filled. So just have look at it if it helps for the next time to choose better answer keys :)

That happens to me on one or two puzzles in every test. Its very difficult to determine keys, there's bound to be a few that go here and there for a few individuals.

Hmm that is possible. as any sudoku can be solved in multiple ways. may be one of the way is such that clues(answer keys) are obtained faster. :p

Are there other samples of these Innovatives available anywhere? (besides the Even Sandwich on p.1 of this thread). Hungry for more! :)

The Solution booklet also has a puzzle history (where the puzzle appeared first time) - but there are no links.

Well, it's only one puzzle, but today's 'friday-noon-puzzle' is an Even Sandwich Sudoku. You can find it here.

Enjoy!

I liked most of the innovatives in this test, and it's very likely that I will make some of the other variants in the future as well. I will keep you all informed about it.

Nice one, quite easy but really pleasant to solve; thank you Richard. Now waiting for the other puzzles you just promised to make!

As promised earlier, I have made a few puzzles that were inspired by this nice sudoku test. Two of my favorite puzzles (Search nine sudoku and Rank sudoku) are already included in the sudoku-advent-calender at Logic Masters Germany, two others (Clones and Between) will appear soon.
You can read more about the advent calender and links to the puzzles in another thread in this forum.