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Theme: The Magic of 23

Author/Opus: This is the 31st puzzle from our contributing puzzlemaster Serkan Yürekli.

Rules: In this variation of Nurikabe, the no 2×2 ocean rule is removed and instead all ocean cells must belong to a single closed loop.

Specifically: Divide the grid into regions called “islands”, each containing exactly one of the given numbers and with the same area as that number. Islands can only touch diagonally. A single closed loop (without intersection or crossings) must be drawn in all remaining cells.

Answer String: Enter the length in cells of the horizontal loop segments from left to right in the marked rows, starting at the top. If the loop only has vertical segments in the marked row, enter 0. Separate each row’s entry with a comma. This example has the key “12,3”.

Time Standards (highlight to view): Grandmaster = 4:45, Master = 6:30, Expert = 13:00

Solution: PDF

Note: Follow this link for classic Nurikabe puzzles on this website and this link for other variations on Nurikabe puzzles. If you are new to this puzzle type, here are our easiest Nurikabe puzzles to get started on.

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or solve online (using our beta test of Penpa-Edit tools)

Theme: An Odd Introduction

Author/Opus: This is the 30th puzzle from our contributing puzzlemaster Serkan Yürekli.

Rules: In this variation of Nurikabe, the no 2×2 ocean rule is removed and instead all ocean cells must belong to a single closed loop.

Specifically: Divide the grid into regions called “islands”, each containing exactly one of the given numbers and with the same area as that number. Islands can only touch diagonally. A single closed loop (without intersection or crossings) must be drawn in all remaining cells.

Answer String: Enter the length in cells of the horizontal loop segments from left to right in the marked rows, starting at the top. If the loop only has vertical segments in the marked row, enter 0. Separate each row’s entry with a comma. This example has the key “12,3”.

Time Standards (highlight to view): Grandmaster = 0:45, Master = 1:20, Expert = 2:40

Solution: PDF

Note: Follow this link for classic Nurikabe puzzles on this website and this link for other variations on Nurikabe puzzles. If you are new to this puzzle type, here are our easiest Nurikabe puzzles to get started on.

(View image directly for larger form.)

PDF

or solve online (using our beta test of Penpa-Edit tools; use Tab to alternate between number entry and shading)

Theme: String Lengths

Rules: Variation of Nurikabe and Scrabble/Criss-Cross puzzles.

Place the 12 number strings into the grid, reading from left to right or from top to bottom, so they are all connected criss-cross style and also form a valid Nurikabe ocean. No unlisted string can appear anywhere, not even two-character ones, and the strings do not occupy any 2×2 area. The remaining white cells are part of islands as in a Nurikabe puzzle. Each island is represented by one number in the grid which equals its size in cells.

Or see this example from the 22nd WPC instruction booklet.

Answer String: For each column from left to right, enter the total count of zeroes from the entered strings. Enter the result as a single string (eg “401120…”)

Time Standards (highlight to view): Grandmaster = 7:00, Master = 15:00, Expert = 30:00

Solution: PDF

PDF

or solve online (using our beta test of Penpa-Edit tools)

Theme: Logic

Rules: Hybrid of Nurikabe and Sashigane, originally created by Grant Fikes. Standard Nurikabe rules are in place for the “ocean” (connected and no 2×2 squares) but the island rules have changed as follows:
1. All islands must be L-shaped and one cell wide. Islands cannot share an edge.
2. An arrow clue points from an end of an island towards the bend in the middle.
3. A circle clue indicates the bend in the middle of an island; if a number is also present, this is the size of the island in cells.
4. An island can have 0, 1, or more of these clues given.

Also see this example and solution by Thomas Snyder:

Answer String: Enter the length in cells of each of the black segments (the unnumbered, connected “ocean”) from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.

Time Standards (highlight to view): Grandmaster = 5:00, Master = 6:30, Expert = 13:00

Solution: PDF

PDF

or solve online (using our beta test of Penpa-Edit tools; use Tab to alternate between letter entry and shading)

Theme: Hidden words (each row of letters forms an English word like SERF.)

Rules: Put each number (given as a word) into the grid, one letter per cell, as a snakelike strip which does not touch or cross itself. Some letters of the words are given. The remaining cells should be painted black to form a continuous wall as in a Nurikabe puzzle with no 2×2 shaded regions. Or see here.

Answer String: Enter the contents of each marked column from top to bottom, using X (capital letter) for each blackened square and capital letters for each island cell, and separating the columns with a comma.

Time Standards (highlight to view): Grandmaster = 2:30, Master = 3:30, Expert = 7:00

Solution: PDF

PDF

or solve online (using our beta test of Penpa-Edit tools; use Tab to go between number entry and shading modes)

This is a “Franken-Friday” puzzle variation.

Theme: Crypt-oceanography

Rules: Standard Nurikabe rules, except the size of each island has been encrypted. Each letter in this puzzle stands for a different positive integer, which must be determined while solving the puzzle. (Formatting note: space has been left in the cells for you to write the actual number values beneath each letter.)

Answer String: Enter the length in cells of each of the black segments (the unnumbered, connected “ocean”) from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.

Time Standards (highlight to view): Grandmaster = 10:00, Master = 15:00, Expert = 30:00

Solution: PDF

PDF

or solve online (using our beta test of Penpa-Edit tools)

This is a “Twisted Tuesday” puzzle variation.

Theme: Unique Islands

Rules: Standard Nurikabe rules. Also, each island shape must be unique. This means that no two islands, including rotation and/or reflection of the shapes, can be superimposed.

Answer String: Enter the length in cells of each of the black segments (the unnumbered, connected “ocean”) from left to right for the marked rows, starting at the top. Separate each row’s entry from the next with a comma.

Time Standards (highlight to view): Grandmaster = 4:15, Master = 6:00, Expert = 12:00

Solution: PDF

In addition to FoxFireX’s incredible sudoku gift that he made for someone’s birthday (some puzzles are meant to keep more private), we got three other submissions for our first Hidden Contest. We’re posting them here in increasing order of difficulty.

First up is an “Anti-Symmetry” Nurikabe from Giovanni P. where every clue that is odd/even has an even/odd clue in the corresponding symmetric place. Standard Nurikabe rules are all you need for this challenge.

Solution image

Next up is a real RARITY for this website, a Shakashaka. For the general rules, we’ll direct you to Nikoli.com where the puzzle originated. Here, Bryce Herdt has made a cipher version of the puzzle. The letters AIRTY each stand for a different number from 0 – 4 which the solver must determine.

Solution image

Finally, the hardest of the bunch, is an intriguing variation called “Sudoku Slitherlink” by its designer Scott Handelman. In addition to standard Slitherlink rules, a different number from 0-3 must go into each green cell. No number in a green cell can repeat in that row or column. As Scott warns, this is one of the hardest puzzles he’s constructed and, from his original post, he’s “still kinda shocked that the middle just kinda ‘works'”.

Solution image

All of these puzzles are grouped in this single PDF.

If you enjoy these puzzles, please comment here and say so, thanking each of the authors. As contest entries, these didn’t go through editorial review (except making sure there was a single answer), but we found them all quite interesting and worthy of being some of the first puzzles from other authors to appear on this web-site. We’re considering keeping Sunday open for “guest” submissions each week from new puzzle authors. And once we get through a stack of puzzle submissions for The Art of Puzzles, more authors will be appearing throughout the week too.