Puzzles:
1. Interesting puzzle. At some points I have to bifurcate for quite some time; I wonder what the logical path is.
2. Very nice, if on the easier side of puzzles.
3. Basically Pencilmark Sudoku. Not particularly interesting, but that's probably because I don't like Sudoku in general.
4. Surprisingly once I got the idea how to do these Build A Maze puzzles, this one falls pretty easily.
5. One of the more interesting puzzles I've had. There's that satisfying a-ha moment when the dice falls and I can finally make progress.
6. Not particularly interesting, either; when a Nansuke puzzle gets past a certain point, it becomes a chore to look through the numbers to find one of satisfying pattern. I just coded a little program to help me find numbers matching a pattern I want. Given that I have to check quite a lot of patterns, I'm not sure if some other solution can shortcut it a lot.
7. Didn't solve; haven't gotten the break-in yet.
8. Didn't solve for the same reason.
9. Very nice idea, actually; this is one puzzle I enjoyed a lot.
10. A very bad idea for a puzzle, because you can actually program it and get the answer in reasonable amount of time (read: 2 seconds), without needing to check all configurations. (When I submitted this, I forgot there's the tiebreaker, but it can still be solved using program even so.)
11. Also a poor idea because theoretically it can still be solved pretty quickly (read: polynomial-time), although this time it won't be so fast. Although that's just me being lazy to think; I'm sure there's a way to get a fast enough program to find the optimal solution.
12. One of my favorite optimizers. Got the right idea, but couldn't figure out how to get one line only. I predicted the winning score to be 1 or 2; apparently there are so many of them.

I put the points for puzzles 11 and 12.
I and Deb discussed the post of Denis. The April Contest participants can check the answers twice, not in a hurry. I will consider offers of Denis in the future.

Preliminary results were published. Max scored seven participants. I congratulate Christian, Dmitry, Ken, Stefano, Takuma, Tomoaki and Tomoya!

En réponse à Anne pour le #11 voici comment j'ai procédé : je trace tous les chemins possibles sans placer les marques, si possible avec des couleurs différentes pour bien les distinguer. Puis je marque toutes les intersections de ces différents chemins deux à deux. C'est a priori sur ces intersections qu'il va falloir placer les trois marques pour rabouter entre eux les chemins les plus longs. Bien sûr on regarde prioritairement les chemins les plus longs et on constate que les intersections se situent fréquemment vers le milieu, ce qui ne sera pas très intéressant car il faudra choisir une direction et l'on aura donc perdu la moitié de la longueur environ. Mais en y regardant de plus près on constate que deux des grandes chaînes possèdent une intersection quasiment à une de leur extrémité. Il n'y a alors plus qu'à regarder si les chemins qui en sont issus se recoupent, ce qui se vérifie et permet donc de positionner les trois marques . . .

Thanks Riad for this wonderful contest. I had a lot of fun as usual.
Could you please check something. I think I also have the max score of 99 points. In puzzle 10 I had 105 names and 561 letters, but I received no points.

i couldnt see what is wrong in my solution below,







Attachments
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q1.png (21KB - 1 downloads)

@duran :
in the green corner at the bottom on the right, there are more X than O...

You're right Hugo, we have eight winners and you're one of them, sincerely congratulations!