Before I get to the rules and the puzzle itself, I’d like to say this first. I understand this puzzle is not for everyone, with some very complex rules and an absolutely enormous level of challenge. But if you’ve come here to enjoy puzzles, you would be missing out by avoiding this one. The solution to this puzzle is a sequence of pure logic, probably with more variety than almost any other grid-based logic puzzle there is, involving virtually no thinking ahead at all. I believe that anyone who perseveres to the end of this puzzle will feel very well rewarded for their efforts. Best of luck.

Now, puzzle 200:

This is a Sunday Nikoli Octathlon puzzle, a unique type. Eight different puzzles have been crunched together and interlocked in a cycle. Each puzzle’s clues are disguised somehow, and only by knowing the solution of the previous puzzle can you figure out the puzzle’s true state. Note that this “true state” may not be uniquely solvable itself, and it may be that you have to use constraints from the next puzzle in line to determine the solution. Detailed rules follow below the image.

Here is the same image, with some helpful extra grids and almost all of the rules written in brief notes outside the grids. Since these rules are kind of long and intimidating, you may wish to get started right away by using this image. The text is not comprehensive and not a full substitute, so you can use the rules below as a reference for the places where the image’s annotations are somewhat ambiguous. Thanks to Alan Curry for the idea of making the image, and also for testsolving the puzzle.

Akari (depends on Hitori, dependee of Shikaku)

See here for the rules to Akari.

The walls are not given to you in this puzzle. The black cells in the solution to the Hitori puzzle are exactly the locations of the walls. Any wall with a number represents a typical numeric clue in Akari. Any number without a wall is a fake clue and should be ignored. Light bulbs are allowed to be placed on top of fake numbers.

Shikaku (depends on Akari, dependee of Heyawake)

See here for the rules to Shikaku.

A lot of extra numbers are given in this puzzle. Overlay the light bulbs in the Akari solution on this puzzle. Only those numbers which have a lightbulb on top of them are true clues in this puzzle. All other numbers should be ignored; they may or may not denote the correct size of the rectangle that contains them.

Heyawake (depends on Shikaku, dependee of Nurikabe)

See here (flash) and here (better English) for the rules to Heyawake.

The rooms are not given to you in this puzzle. The rectangles in the solution to the Shikaku are where the rooms are. Only those numbers appearing in the top left cell of a room should be used as clues. All other numbers should be ignored.

Nurikabe, featuring Kurodoko (depends on Heyawake, dependee of Fillomino)

See here for the rules to Nurikabe. See here and here for the rules to Kurodoko (which is sometimes called Kuromasu).

A Nurikabe and a Kurodoko puzzle have been superimposed on each other. The solution to the Heyawake puzzle and the Kurodoko puzzle are identical. Each number in this puzzle is the location of a clue in both the Nurikabe and Kurodoko, and the number is the sum of the clues in each of the puzzles (i.e. if there is a Nurikabe 1 and a Kurodoko 6 in the same space, a 7 will appear in this puzzle).

Fillomino (depends on Nurikabe, dependee of Country Road)

See here for the rules to Fillomino.

A lot of extra numbers are given in this puzzle. Overlay the Nurikabe solution on this puzzle. All numbers covered by a black cell in the Nurikabe solution are liars and are not the correct number. All numbers covered by white cells are truth-tellers.

Country Road (depends on Fillomino, dependee of Corral)

See here for the rules to Country Road.

The rooms are not given to you in this puzzle. Overlay the Fillomino solution; it gives the shape of all of the rooms. Each room will contain no number or one number, which functions as a standard Country Road clue for that room. The number can appear in anywhere in the room.

Corral, featuring Masyu (depends on Country Road, dependee of Hitori)

See here for the rules to Corral. See here for the rules to Masyu.

The grid is filled with Corral clues in black or white circles, but not all of the Corral clues are correct. Overlay the solution to the Country Road puzzle on this one. Cross off all of the circled numbers for which that colored circle would not be a valid Masyu clue in the Country Road solution. All of the numbers that are left are the clues to the Corral puzzle. (the numbers that are crossed off may or may not be correct)

Hitori, featuring Slitherlink (depends on Corral, dependee of Akari)

See here (flash) and here (better English) for the rules to Hitori. See here for the rules to Slitherlink.

A Hitori and a Slitherlink puzzle have been superimposed on each other. The solution to the Corral puzzle and the Slitherlink puzzle are identical. The Slitherlink puzzle gives a number in every square, just as the Hitori does. All of the Hitori clues are numbers from 1 to 10. Each number that appears in this puzzle is the units digit of the sum of the Hitori and Slitherlink clues. For instance, in a space where the Slitherlink has a 3 and the Hitori has an 8, a 1 would be written in this puzzle.

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Tags: game, logic, nikoli, problem, puzzle