[This is a repost from our archives with new notes at the top (original post here): A good sudoku variant adds a small amount of new thinking on top of the basic Sudoku (three-way no repeat) rule; Arrow Sudoku fits that description perfectly with a few arithmetic deductions added on top of standard sudoku, and the potential for graphically interesting themes. This Arrow Sudoku puzzle should break apart easily once the “new” Arrow rule is properly considered.]

PDF

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

Theme: Diagonals (two more than yesterday!)

Rules: Standard Arrow Sudoku rules. Range is 1-6.

Estimated Difficulty*: 1 star

Time Standards (highlight to view): Grandmaster = 0:40, Master = 1:15, Expert = 2:30

Solution: PDF

Note: Follow this link for more Arrow Sudoku. If you are new to this puzzle type, here are our easiest Arrow Sudoku to get started on. More Arrow Sudoku puzzles can be found in The Art of Sudoku 2 and Masterpiece Sudoku Mix 3.

[This is a repost from our archives with new notes at the top (original post here): One of my favorite “underappreciated” puzzle styles is Cave, a genre that began as BAG from Nikoli (with rules consistent with other loop puzzle styles). The style passed through other names like Corral in the United States Puzzle Championship before being recast as a shading puzzle as Cave which is the GMPuzzles name. While the shading approach feels most natural to me, it does have one slight disadvantage from the loop version which is solvers need to learn an anti-checkerboard rule for themselves (i.e., you cannot have a 2×2 square which alternates between inside/outside cells as on a checkerboard). In the “loop” version of the rules, that grid state would require drawing four edges through a point and would violate the non-intersecting loop rule.

However you want to refer to this puzzle style, we hope that you enjoy this look back at some of the first Cave puzzles on the GMPuzzles site starting with this one featuring a long diagonal of clues.]

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: Ascending/Descending Diagonal

Rules: Standard Cave rules.

Estimated Difficulty*: 1.5 stars

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

Solution: PDF

Note: Follow this link for classic Caves and this link for Cave variations. If you are new to this puzzle type, here are our easiest Cave Puzzles to get started on. More Cave puzzles can be found in Roger Barkan’s Colossal Cave Collection, in The Art of Puzzles, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

[This is a repost from our archives with new notes at the top (original post here): This very tough Star Battle from our early 2013 posts had an unusual grid layout. If I were to revisit this theme, I might use tools/different ideas to avoid the shaded cells which are not very common in our Star Battle puzzles. But even with these markings the logical path is a great example of human-designed puzzles with intriguing Aha moments.]

PDF

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

Theme: Boxed In (but it plays out differently than yesterday’s “Boxed In”)

Rules: Standard Star Battle rules. Two stars per row, column, and region.

Estimated Difficulty*: 4.5 stars

Time Standards (highlight to view): Grandmaster = 6:45, Master = 13:30, Expert = 27:00

Solution: PDF and solving video.

Note: Follow this link for other classic Star Battles and this link for Star Battle variations. If you are new to this puzzle type, here are our easiest Star Battles to get started on. More Star Battle puzzles can be found in The Art of Puzzles, in the books Star Battle and Star Battle 2, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

[This is a repost from our archives with new notes at the top (original post here): Taking the thermometer shapes to an extreme, “clueless” puzzles like this one are often some of the most interesting Thermo-Sudoku puzzles and require carefully considering the interplay of shapes and digit ranges. Our first week of Thermo-Sudoku puzzles ended with this “Boxed In” challenge with 5 main thermo shapes and no given numbers.]

PDF

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

Theme: Boxed In

Rules: Standard Thermo-Sudoku rules.

Estimated Difficulty*: 3.5 stars

Time Standards (highlight to view): Grandmaster = 5:00, Master = 9:00, Expert = 18:00

Solution: PDF and solving video.

Note: Follow this link for other Tight Fit Sudoku puzzles on this website. If you are new to this puzzle type, here are our easiest Tight Fit Sudoku to get started on. More Tight Fit Sudoku can be found in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli and in Masterpiece Sudoku Mix 2.

[This is a repost from our archives with new notes at the top (original post here): In this Star Battle, the second posted on the site, a common cage shape theme is used multiple times to lead to a logical solving path.]

PDF

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

Theme: Crossed Crosses

Rules: Standard Star Battle rules. Two stars per row, column, and region.

Estimated Difficulty*: 2 stars

Time Standards (highlight to view): Grandmaster = 1:15, Master = 2:30, Expert = 5:00

Solution: PDF

Note 2: Follow this link for other classic Star Battles and this link for Star Battle variations. If you are new to this puzzle type, here are our easiest Star Battles to get started on. More Star Battle puzzles can be found in The Art of Puzzles, in the books Star Battle and Star Battle 2, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

[This is a repost from our archives with new notes at the top (original post here): Symmetrically marked cells are one of the easier themes to achieve with Thermo-Sudoku, and in this puzzle the double zeroes highlight a few different kinds of logic to get to the unique solution.]

PDF

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

Theme: Double Zeroes

Rules: Standard Thermo-Sudoku rules.

Estimated Difficulty*: 2 stars

Time Standards (highlight to view): Grandmaster = 2:15, Master = 3:30, Expert = 7:00

Solution: PDF

Note: Follow this link for more Thermo-Sudoku puzzles. If you are new to this puzzle type, here are our easiest Thermo-Sudoku to get started on. More Thermo-Sudoku puzzles can be found in The Art of Sudoku 2 and in Masterpiece Sudoku Mix 2.

[This is a repost from our archives with new notes at the top (original post here): Star Battle, which was originally designed by Hans Eendebak for the 2003 World Puzzle Championship, is one of our favorite object placement styles. The region constraints and no touching constraints lead to a lot of different logic. While there are computer-generated versions of this style in major newspapers now, the hand-crafted themes and logical flows of this puzzle are what we look for with any Grandmaster Star Battle.]

PDF

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

Theme: Downward Spiral

Rules: Standard Star Battle rules. One star per row, column, and region.

Estimated Difficulty*: 1.5 stars

Time Standards (highlight to view): Grandmaster = 0:45, Master = 1:15, Expert = 2:30

Solution: PDF

Note 2: Follow this link for other classic Star Battles and this link for Star Battle variations. If you are new to this puzzle type, here are our easiest Star Battles to get started on. More Star Battle puzzles can be found in The Art of Puzzles, in the books Star Battle and Star Battle 2, and in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli.

[This is a repost from our archives with new notes at the top (original post here): Greater than/less than constraints can lead to good forcing chains in different number puzzles. However, I’ve never been a fan of using lots of < and > shapes (particularly when rotated 90 degrees) as that notation only works well across pairs of cells and not across chains of connected cells. I created Thermo-Sudoku as a new presentation method to make multi-cell constraints more easily seen and allow for graphically interesting themes. I first developed the style and name while planning for the book Mutant Sudoku with Wei-Hwa Huang, with imagery of a “melted thermometer in the boiling sudoku solution being poured out on paper” as the first mutation caused by Dr. Sudoku’s mistakes in the lab.]

PDF

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

Theme: Grandmaster Puzzles (the G and P shapes in the corners)

Rules: Standard Thermo-Sudoku rules. Range is 1-6.

Estimated Difficulty*: 1 star

Time Standards (highlight to view): Grandmaster = 0:40, Master = 1:00, Expert = 2:00

Solution: PDF

Note: Follow this link for more Thermo-Sudoku puzzles. If you are new to this puzzle type, here are our easiest Thermo-Sudoku to get started on. More Thermo-Sudoku puzzles can be found in The Art of Sudoku 2 and in Masterpiece Sudoku Mix 2.

[This is a repost from our archives with new notes at the top: This Tight Fit Sudoku (original post linked) goes to eleven! While most Tight Fit sudoku use the range of 1-9, these larger grids — in this case one that has already filled all the “big cells” and only has Tight Fit cells left — can stretch your mind and your notation in interesting ways.]

PDF

or solve online (using our beta test of Penpa-Edit tools; use tab to alternate between Sudoku = big digits and Number candidate = small entries in the corners of cells.)

Theme: The patterned digits in this Tight Fit Sudoku set up an interesting logical solve.

Rules: Standard Tight Fit Sudoku rules. Range is 1-11.

Estimated Difficulty*: 3 stars

Time Standards (highlight to view): Grandmaster = 3:45, Master = 7:30, Expert = 15:00

Solution: PDF and solving video.

Note: Follow this link for other Tight Fit Sudoku puzzles on this website. If you are new to this puzzle type, here are our easiest Tight Fit Sudoku to get started on. More Tight Fit Sudoku can be found in our beginner-friendly collection Intro to GMPuzzles by Serkan Yürekli and in The Art of Sudoku 2.

[This is a repost from our archives with new notes at the top: The final Nurikabe (original post) of week two was one of our “best of” puzzles in our launch year 2013, with an interesting visual clock theme and again a different kind of use of wide open white spaces for that unexpected number (if it was going to be anything, it had to be a 13! There might come a time you might need a clock that can point at that).]

PDF

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

Theme: Nurikabe Time; don’t wait for the 13th hour to figure out where all the clock islands go.

Rules: Standard Nurikabe rules.

Estimated Difficulty*: 3 stars

Time Standards (highlight to view): Grandmaster = 2:00, Master = 5:00, Expert = 10:00

Solution: PDF and solving video; advice on solving this puzzle has also been posted in “Ask Dr. Sudoku #2“.

Note: Follow this link for classic Nurikabe and this link for Nurikabe variations. If you are new to this puzzle type, here are our easiest Nurikabe puzzles to get started on. More Nurikabe puzzles can be in The Art of Puzzles, in our beginner-friendly book Logic Puzzles 101, and in the e-book Nurikabe by Ashish Kumar.