Best of luck and skill to all competitors in Kraków, Poland this week at the World Sudoku and Puzzle Championships (WSPC).

PDF

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

Theme: US Team for 2022 World Sudoku and Puzzle Championships

Author/Opus: This is the 424th puzzle from Thomas Snyder, aka Dr. Sudoku.

Rules: This puzzle from the US team t-shirts for the world championships is originally being released in an “instructionless” mode. It combines a common sudoku variation and a common puzzle type. More info is now available below.

Identity of the two rule sets: (highlight to view): This puzzle combines Thermo-Sudoku and Skyscraper styles. The combination of this style with no givens was first constructed by Thomas Snyder for the 2013 United States Puzzle Championship.

Solution: PDF; the puzzle was featured in a Cracking the Cryptic solving video here.

Prasanna is celebrating two milestones this week and we will have two special large puzzles. The first one here recognizes Prasanna’s 200th submission on GMPuzzles, and combines three of the styles where Prasanna has written books for our e-store.

(view directly for a larger image)

PDF

or solve online (using our beta test of Penpa-Edit tools; while solution checking is not enabled, if you are comfortable with the different tool selection options you should be able to fully solve the puzzle in this mode too.)

Theme: Linking 200 cells

Author/Opus: This is the 200th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules:

Grids 1-2: Follow regular LITS rules. Between the two LITS grids, the corresponding white cells can never both be shaded, while the corresponding gray cells must be identical in the three 200-shaped regions.

Use the LITS solutions and your ingenuity to discover the needed constraints for Grids 3-4. For Grid 3, you will find that some gray circles must change color to white or black.

Grid 3: Follow regular Balance Loop rules. Additionally, the loop must cross itself if it passes through a gray circle. The loop must go straight throught the gray circle both times; in one direction the path behaves as if the circle is white with equal loop lengths, and in the other direction the path behaves as if the circle is black with unequal loop lengths. It is not required that the loop pass through all of the gray circles (but it must pass through all white and black circles). (See also the image below.)

Grid 4: Follow regular Yajilin rules.

When taken together, the grids yield a short final answer! Send this (less than five character) string to hiddencontest at gmpuzzles dot com by March 14th, 2021 to be eligible to win an e-book by Prasanna Seshadri. The contest is now closed and results summarized here.

Difficulty: 5 stars?

Solution: PDF

(View image directly for larger form.)

(After solving the puzzle (or before, if you desire) look at this additional image for another challenge.)

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the linex mode where left click+drag draws lines and right click marks X’s. Note that the default puzzle info is too long — even for an url shortener — so copy and paste all the text in this file into the “Load” option in the upper-right of the penpa-edit interface to access. You can then also open a new tab and copy in all this file for the final additional challenge.)

Theme: Clue Symmetry and Logic

Author/Opus: This is the 100th puzzle from our contributing puzzlemaster Prasanna Seshadri.

Rules: This puzzle combines styles that involve shading cells. All rules are standard for the given puzzle types (Tapa, Light and Shadow, Nurikabe, Kurotto, and Cave) which appear in the indicated spots of the grid (see below).

Tapa: Shade some empty cells black to create a single connected wall. Numbers in a cell indicate the length of consecutive shaded blocks in the neighboring cells. If there is more than one number in a cell, then there must be at least one white (unshaded) cell between the black cell groups. Cells with numbers cannot be shaded, and the shaded cells cannot form a 2×2 square anywhere in the grid.

Cave: (The inside of the cave with the numbered cells is shaded here!) Shade some cells to form a single connected group — the cave — with no enclosed, unshaded cells. In other words, all unshaded cells must be connected by other unshaded cells to an edge of the grid. All numbered cells must be a part of the cave, with each number indicating the total count of cells connected vertically and horizontally to the numbered cell including the cell itself.

Additionally, there are two diamonds made out of cells in each grid. Each cell in the smaller diamond corresponds to two cells in the same position in the larger diamond (see example below). The corresponding cells must differ in their shading (i.e., if a cell in the smaller diamond is shaded, both corresponding cells in the larger diamond are unshaded; if a cell in the smaller diamond is unshaded, both corresponding cells in the larger diamond are shaded).

Answer String: Enter the answer to the additional challenge in ALL CAPITAL LETTERS (no spaces)

Time Standards (highlight to view): Grandmaster = 25:00, Master = 32:30, Expert = 1:05:00

Solution: PDF

Serkan finished this “Giant” puzzle shortly after we started our break. We figured this Gapped Kakuro would be a fun, challenging Sunday Surprise that might take several Sundays to complete.

(view directly for a larger image)

PDF

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

Theme: Sum Time

Author/Opus: This is the 72nd puzzle from our contributing puzzlemaster Serkan Yürekli.

Rules: Standard Kakuro Rules. Also, some cells may remain empty but empty cells cannot share an edge with other empty cells.

Answer String: Enter the values in the white cells in the marked rows from left to right, ignoring all black cells, and separating the rows with a comma. Use a capital ‘X’ for any blank cell.

Time Standards (highlight to view): Grandmaster = 50:00, Master = 1:30:00, Expert = 3:00:00

Solution: PDF

Note: Follow this link for other Kakuro puzzles.

For those who thought there would be no special puzzles on Sundays in 2014: SURPRISE!

This very creative submission comes from Nikolai Beluhov. And like his earlier Matryoshka Fillomino, this is a gift that keeps on giving. Starting with a challenging Fillomino puzzle, erasing all of the 4s leaves a Slitherlink. Then erasing all of the 3s leaves a Tapa. Then erasing all of the 2s gives a Simple Loop (treating the 1s as blackened cells).

PDF

Fillomino

Slitherlink

Tapa

Simple Loop

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between a Composite Edgesub mode for Fillomino and Slitherlink, a shading mode for Tapa, a number entry mode for Fillomino, and a line drawing mode for Simple Loop.)

Rules: Standard Fillomino rules.
Then standard Slitherlink rules.
Then standard Tapa rules.
Then Simple Loop rules (draw a single closed loop, without intersections or crossings, through all empty cells; cells with 1s cannot be visited by the loop).

Answer String: None for this puzzle; simply click solved if finished.

Solution: PDF

I’m sure many of you were expecting ANOTHER version of the Christmas Tree puzzle from the last two weeks. I mean, I did get a very nice Double Back from Robert Vollmert (which cannot be confused as a Star Battle or a LITS). But posting such a puzzle wouldn’t be a surprise.

No, today’s Sunday Surprise comes from the pile of submissions I’ve received over the year from Hans van Stippent, who played with the usual rules of Skyscrapers a bit by hiding some of the cells from consideration. It yielded a very interesting puzzle which is Hans’ gift to you this Sunday.

PDF

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

Theme: New Variation/Logic

Rules: Standard Sudoku rules. Also, standard Skyscrapers rules. Additionally, the cells in gray are “underground” and cannot be seen for any of the outside skyscraper clues (think of them as starting with a negative sign if necessary). As an example, the 4 in row 2 refers only to seeing four buildings in columns 3 through 7, even if there is a 9 in column 1 or column 2 as that 9 cannot be seen.

Answer String: Enter the 1st row from left to right, followed by a comma, followed by the 9th row from left to right.

Solution: PDF

Today’s Surprise originated from an unintended mistake. Despite a puzzle labeled “Star Battle” and a graphic with a “2 star” label at the top, Friday’s puzzle was attempted by first one and then many solvers out of curiosity as a LITS. While I’ve seen a Star Battle that can double as a LITS, this was not originally one of them and it is not a typical property to have.

Undaunted by the challenge, Tapio Saarinen (ArDeeJ) sent along a modification of my puzzle into a LITS. After some tweaks by me, we have a Christmas Tree LITS puzzle with very few changes from the original (see this crude sketch). Enjoy the gift that keeps on giving!

PDF

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

Theme: Christmas Tree LI(gh)TS

Rules: Standard LITS rules.

Or, if you prefer to treat this as a Star Battle for some unknown reason, use these rules: In this variation of Star Battle, place the indicated number of stars in each row, column, and region. Then shade exactly four connected cells (without stars) in each outlined region, to form an L, I, T, or S tetromino, so that the following conditions are true: (1) All shaded cells are connected with each other; (2) No 2×2 group of cells can be entirely shaded black; (3) When two tetrominoes in adjacent regions share an edge, they must not be of the same type (L, I, T, or S), regardless of rotations or reflections.

Answer String: Enter the length in cells of each of the shaded segments from left to right for the marked rows, starting at the top. Separate each row’s entry with a comma.

Solution: PDF

Today’s surprise comes from Nikolai Beluhov, a graduate student of mathematical logic who has been sharing some creative puzzle ideas with me recently. Some of them have ended up on his new puzzle blog Puzzled By Titles. This puzzle has become a Sunday Surprise.

Much like a set of Matryoshka dolls, this Fillomino is a puzzle with many layers. Remove the outer border and a new valid Fillomino arises. Keep doing this all the way down to the very center where a 2×2 puzzle awaits. The layers have a wide variety of difficulty and required logical strategies. Can you solve them all?

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between a composite mode for line/edge drawing and a number entry mode.)

Theme: Matryoshka (nesting property) across 5 puzzles

Rules: Standard Fillomino rules.

Answer String: For each puzzle from largest (10×10) to smallest (2×2), enter the numbers placed in each cell along the upper-left to lower-right diagonal in order. Separate each puzzle’s entry by a comma (Your answer will be of the form AAAAAAAAAA,BBBBBBBB,CCCCCC,DDDD,EE).

Solution: PDF

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

Today’s surprise originally comes from Hans van Stippent, with some edits by me (Thomas Snyder) to increase the challenge and rewards of the solve. Together, we present this creative “Mystery Tapa” where all the clues (any value from 1-8) have been replaced with ?’s.

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to shift between shading mode and the composite Yajilin mode where left click marks cells, right click marks dots in cells or X’s on edges, left click+drag draws lines.)

Theme: Clueless?

Rules: Variation of Tapa rules. All clue numbers (1 and above) have been replaced with question marks.

Answer String: Enter the length in cells of each of the shaded segments from left to right for the marked rows, starting at the top. Separate each row entry from the next with a comma. A double-digit number should have both digits entered.

Solution: PDF

Editor’s Note: While our Sunday Surprises are meant to be unexpected, today’s surprise should be a double surprise for you. Besides the bonus puzzle, it is my great pleasure to announce that one of the world’s best puzzlemakers and the inventor of Tapa, Serkan Yürekli, is joining us as a regular contributor. (If you haven’t yet, you should check out his Tapa Variation Contests that are starting again this weekend and his Classic Tapa Contest that starts next week.)

I asked Serkan, for his debut week, to provide some of the puzzle styles I know him best for and I hope you will enjoy what is in store. Today brings a “The Persistence of Memory” puzzle that Serkan wrote with GMPuzzles in mind.

(View image directly for larger form.)

(PNG with extra lines for solvers who want to flood-fill the path)

or solve online (using our beta test of Penpa-Edit tools using a composite mode where left click inside cell shades square, left click + drag draws line segment, right click inside cell adds dot, and right click on cell edge adds an x.)

PDF

Theme: GMPuzzles

Rules: Find a path from one dot to the other by moving horizontally or vertically between adjacent squares. The path cannot touch itself, even diagonally. All highlighted regions must be used, and may be re-entered. If two or more highlighted regions have the same shape and orientation, then how the path passes through those shapes must be identical. Or see here.

Answer String: For each marked row, enter the size of each group of cells used by the path from left to right. Separate each row with a comma.

Time Standards (highlight to view): Grandmaster = 7:30, Master = 10:30, Expert = 21:00

Solution: PDF