PDF

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

Theme: Surprise Sudoku

Rules: Standard Sudoku rules. Also, there is a mystery rule that must be determined by looking at the example at the top of the puzzle.

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

Time Standards (highlight to view): Grandmaster = 6:15, Master = 8:30, Expert = 17:00

Solution: PDF

Editorial Note: While this is an original sudoku for GM Puzzles, this particular “surprise” gimmick from Serkan first appeared on the SudokuCup 10 test with a different puzzle.

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)

Theme: Dominoes — in both the clues and the variation rules

Rules: Standard Cave rules. Also, the exterior of the cave (the cells not seen by the numbers) must be divisible into dominoes (1×2 rectangles) in at least one way.

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

Time Standards (highlight to view): Grandmaster = 4:15, Master = 9:00, Expert = 18:00

Solution: PDF and solving animation.

Note: Follow this link for other classic Caves. If you are new to this puzzle type, here are our easiest Cave Puzzles to get started on.

(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: T

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’s entry with a comma.

Time Standards (highlight to view): Grandmaster = 2:45, Master = 5:30, Expert = 11:00

Solution: PDF

PDF

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

Theme: Clue Symmetry and Logic

Rules: Variation of Skyscrapers rules. Place digits 1-6 into the grid so that no digit is repeated within a row or column. Digits outside the grid indicate the number of buildings that can be seen from the corresponding direction. The buildings form two-digit numbers and the relations between some numbers are shown with a greater than/less than sign.

Or, see here.

Answer String: Enter the 3rd row from left to right, followed by a comma, followed by the 4th column from top to bottom.

Time Standards (highlight to view): Grandmaster = 5:15, Master = 7:30, Expert = 15:00

Solution: PDF

PDF

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

Theme: Trapped in A box

Rules: Either shade or add a single letter (A, B, or C) to each square so that each row and column contains exactly one A, one B, one C, and the rest shaded squares. Cells in the grid already marked with a letter can be shaded or remain unchanged.

Letters outside the grid indicate the first letter seen from that direction.

Numbers outside the grid describe the size of groups of consecutive shaded squares in that row or column in order. There must be at least one unshaded square between groups.

Or, see here.

Answer String: Enter the number of the column where the B is placed in each row, starting with the top row and proceeding to the bottom.

Time Standards (highlight to view): Grandmaster = 4:30, Master = 5:45, Expert = 11:30

Solution: PDF

PDF

or solve online (using our beta test of Penpa-Edit tools in edgex mode where left click+drag draws lines and right click marks X’s)

Theme: Unfriendly Neighbors

Rules: Standard Slitherlink rules. Also, there are some sheep (marked S) that must be inside the loop and some wolves (marked W) that must be outside the loop.

Answer String: Enter the length in cells of each of the internal loop segments following the arrows for the marked rows, starting at the top. Separate each row’s entry with a comma.

Time Standards (highlight to view): Grandmaster = 2:15, Master = 3:00, Expert = 6:00

Solution: PDF

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between ship placement, shading, and number entry modes. In ship placement mode, right click gives sea, left click gives circle/square, left click and drag for rounded ships.)

Theme: Logical

Rules: Hybrid of Battleships and Criss-Cross (Nansuke) puzzles:

Place the given fleet into the grid so that no two ships touch, even diagonally. In the remaining unused cells, place the given numbers criss-cross style so that they can be read from left to right or from top to bottom. All possible entries with two or more connected digits are given.

Answer String: Entry the contents of the two marked columns from top to bottom, using a capital X for any cell with a ship segment.

Time Standards (highlight to view): Grandmaster = 4:00, Master = 10:30, Expert = 21:00

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)

Theme: Clue Symmetry and Logic

Rules: Variation of Skyscrapers rules. Place digits 1-6 into the grid so that no digit is repeated within a row or column. Digits outside the grid indicate the number of buildings that can be seen from the corresponding direction. The buildings form two-digit numbers and the relations between some numbers are shown with a greater than/less than sign.

Or, see here.

Answer String: Enter the 2nd row from left to right, followed by a comma, followed by the 4th row from left to right.

Time Standards (highlight to view): Grandmaster = 2:15, Master = 3:15, Expert = 6:30

Solution: PDF

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