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.

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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!

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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?

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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.

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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

I had not intended to have a repeat author for a Sunday Surprise so soon, but Craig Kasper sent along a really nice surprise sudoku to mark the US National Championship we’ve been focusing our attention on all weekend. See if you can find your way through to the very end.

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Theme: That US national championship happening this weekend; speaking of which, congratulations to the top finishers at the US Puzzle Championship, whomever you turn out to be.

Rules: Standard Sudoku rules. Also, the regions are irregularly shaped; instead of numbers, use the letters in “I’D GOLF, MAN” once in each row, column, and region.

Answer String: Enter the letters in the third column, from top to bottom, followed by the letters in the seventh column, from top to bottom. USE CAPITAL LETTERS.

Solution: PDF

Today’s surprise comes from Hans van Stippent, who sent several creative submissions in for The Art of Puzzles. For this book I’m mostly avoiding “variations”, but I found this puzzle to be a surprising twist perfect for this spot.

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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: Diagonals

Rules: Variation of standard Fillomino rules. Some clues are not fully specified, and must simply follow the inequality value given in the cell.

Answer String: For each cell in the marked rows/columns, enter the area of the polyomino it belongs to. Start with the 2nd row, followed by a comma, followed by the 8th row.

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 comes from Tyler Hinman, five-time winner of the American Crossword Puzzle Tournament and author of Winner’s Circle Crosswords. I’ve had the pleasure of co-solving with Tyler — whom I call “Kid Crossword” when in “Dr. Sudoku” mode — on many puzzle hunts in recent years and we’ve had a number of good conversations on puzzle design. Total Masyu, which appeared again this Tuesday, for example was an idea that came up in one such chat from Tyler that I constructed for my blog.

As I heard from Tyler a few months ago: “Here’s a weird idea I had the other night while unable to sleep. … It’s inspired by the Spy piece in Stratego, which wins a battle if it attacks the highest-ranked piece (the Marshal), but loses under all other circumstances.” The concept was for Spy Futoshiki, the subject of today’s surprise, where the lowest value (1) is considered greater than the highest value (5), but all other inequalities obey normal ordering. It’s a clever idea and Tyler’s provided a very nice puzzle to demonstrate the change.

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Theme: Spies among us

Rules: Insert a number from 1-5 into each square so that each number appears once in every row and column. Inequality signs between the boxes indicate the larger/smaller numbers, with the single exception that the number 1, the “Spy”, is considered larger than the number 5 if in adjacent cells.

Answer String: Enter the 1st column from top to bottom, followed by a comma, followed by the 5th column from top to bottom.

Solution: PDF

This past week, another doctor made the mistake of appearing here. It seems trouble follows him everywhere, as puzzle creator Craig Kasper reveals here.

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Theme: Dalek Invasion

Rules: Standard Sudoku rules except that instead of the numbers 1-9 this puzzle uses the letters in “END MATRIX”. Also, clues in the grid represent typical “Seek and Spell/Kanaore” clues; specifically, it must be possible to read each of the words/phrases listed below the grid by starting at the indicated number, moving one cell in the direction indicated by the arrow, and then continuing to move one cell at a time up, down, left, or right to complete the word/phrase. No cell may be used more than once in a single path, but the same cell can appear in the paths of different words/phrases.

Answer String: Enter the 2nd row from left to right, followed by a comma, followed by the 6th row from left to right. Use all capital letters.

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.

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Theme: Guess the author?

Rules: Variation of standard TomTom rules. In these puzzles, the five numbers to enter are not 1-5. In each grid, there are five unknown integers that the solver must determine.

Answer String: Enter the 3rd row from left to right in the left puzzle, followed by a comma, followed by the 3rd row from left to right in the right puzzle.

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

Solution: PDF

**While this was initially not a numbered opus in this author’s work, we are calling it #47 for our site count.