Puzzles on this page may require a bit of thought and some comfort with variant techniques. Puzzles are added in reverse chronological order so newer puzzles are at the top. This collection includes puzzles from April 2022 - current. For earlier puzzles, explore Indigestion Collection 1.

This one is all about finding the break-in.

Estimated difficulty: 3/5

*Rules*

Normal sudoku and killer cage rules apply. Every row, column, and box must contain a complete set of the digits 1-9.

Digits along arrows must sum to the value shown in the attached circle. Digits can repeat along arrows if allowed by other rules.

For once, no fog and no killer cages!

Estimated difficulty: 2.5/5

*Rules*

Normal sudoku and killer cage rules apply. Every row, column, and box must contain a complete set of the digits 1-9.

Little killers: Numbers outside the grid give the sum of all digits along the indicated diagonal. Digits may repeat along the little killer diagonal if permitted by other rules.

Despite the plethora of thermometers, this is a rather difficult puzzle requiring advanced solving techniques for the break-in.

Estimated difficulty: 2.5/5

*Rules*

Normal sudoku rules apply: every row column and 3x3 box must contain a complete set of the digits 1 through 9.

Normal killer cage rules apply: the digits in a cage cannot repeat and must sum to the number in the top left corner of the cage.

Normal anti-knight rules apply: cells separated by a chess knight's move cannot contain the same digit.

Path construction, fog of war, and modular lines ... what a delicious combination! This puzzle was featured on Cracking the Cryptic as *The Drunkard's Walk** *on 23 November 2022. It inspired this lovely limerick by Amos Wittenberg in the comments on the video, included here with permission from the author:

A drunkard whose brain lacked all clarity

Walked home with bizarre regularity.

It may sound impossible,

As the fog was an obstacle

But his path had perfect modularity!

Estimated difficulty: 2.5/5

*Rules*

After a night of celebrating, our hero leaves r1c1, through the fog, trying to get home to r9c9. With each step, they move to an orthogonally adjacent cell, forming a modular line as they go. (That means any set of three contiguous digits along their path must include one each from {147}, {258}, and {369}.)

They stagger from streetlamp to streetlamp as they go, each represented by a yellow disk in a cell. Some of the streetlamps are visible from the start but others are hidden by the fog and will only be revealed when correct digits are placed nearby. Their path must lead them to every streetlamp. All streetlamps are from the same modular set and whenever a number from that set is on the path, it appears as a streetlamp. Numbers from that modular set which are not on the path are not streetlamps.

If our hero enters a killer cage, they must completely traverse the cage before exiting it. Some killer cages may be avoided entirely.

Normal sudoku and killer cage rules apply. Every row, column, and box must contain a complete set of the digits 1-9. Digits inside cages indicated by dashed lines cannot repeat and must sum to the value in the upper left corner of the cage, if given.

Examining the intricate interplay of thermometers, Hot Cycles also appears in Indigestion Collection 2.

Estimated difficulty: 2/5

*Rules*

Standard sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9.

Digits on thermometers must increase from bulb to tip.

The purest of knights gives the title for this puzzle, which also appears in Indigestion Collection 2.

Estimated difficulty: 2/5

*Rules*

Normal sudoku rules apply: every row column and 3x3 box must contain a complete set of the digits 1 through 9.

Normal anti-knight rules apply: cells separated by a chess knight's move cannot contain the same digit.

Originally published as part of the CTC Fan Discord 8K Archive Puzzles Milestone Pack curated by BenceJoFul. It also appears in our GAS Collection 2.

Estimated difficulty: 1.5/5

*Rules*

Normal 8x8 sudoku rules: every row, column, and box must contain a complete set of the digits 1-8.

Normal killer cages: digits within a cage cannot repeat and must sum to the number shown in the upper left (in this puzzle, always to 8).

Digits on thermometers must increase from bulb to tip.

A follow-up to Residual Skylines, this puzzle uses hidden modular lines instead of an entropic condition for building skyscrapers. It also appears in our Indigestion Collection 2.

Estimated difficulty: 3/5

*Rules*

Normal sudoku rules apply: every row, column, and box contains a complete set of the digits 1-9.

The value of each cell gives the height of the skyscraper occupying that cell. Taller skyscrapers hide smaller skyscrapers. Clues outside the grid indicate the number of skyscrapers seen along that row or column from the direction of the clue. The skyscrapers between the clue and the tallest skyscraper in that sightline form a modular line, including the tallest skyscraper and hidden buildings as part of the modular line.

On modular lines, every set of three contiguous cells contains one digit from {147}, one from {258}, and one from {369}.

Solve in the Sudokupad app with solution checker

We set this puzzle to highlight a particular mathematical property and stunning pattern that emerges from a simple constraint. It was featured on Cracking the Cryptic as *A Modular Miracle* on 31 August 2022. It also appears in our Showcase Puzzles.

Estimated difficulty: 3.5/5

*Rules*

Normal sudoku rules apply: every row, column, and 3x3 box must include a complete set of the digits 1-9.

Killer cages: digits within cages marked by dashed lines must sum to the number shown in the upper left corner of the cage.

Every diagonal of length 7, 8, or 9 is either modular or unimodular. On modular lines, every set of three sequential digits contains one digit from {147}, one from {258}, and one from {369}. On unimodular lines, all digits are from the same class (all from {147} or all from {258} or all from {369}).

A harder version of Box Twist, Starburst first appeared in the Caging Constraints puzzle pack by BremSter.

Estimated difficulty: 3/5

*Rules*

Normal sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9.

Normal killer sudoku rules apply: digits inside a cage marked by dashed lines cannot repeat and must sum to the number shown in the upper left corner.

Modular lines: every set of three sequential digits along a line must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}. Digits may repeat on a line if allowed by other rules.

This puzzle was set for, and initially appeared in, the Caging Constraints puzzle pack curated by BremSter. You can find the entire puzzle pack here.

Estimated difficulty: 2.5/5

*Rules*

Normal sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9.

Normal killer sudoku rules apply: digits inside a cage marked by dashed lines cannot repeat and must sum to the number shown in the upper left corner.

Normal disjoint groups rules apply: digits in the same relative position within different 3x3 boxes must be different.

When this puzzle was set, temperatures across the globe were hitting record extremes (high or low depending on location). It combines modular line logic with thermometers. This puzzle also appears in Indigestion Collection 2. We were quite pleased to have it featured on BremSter's channel on 9 August 2022.

Estimated difficulty: 2.5-3/5

*Rules*

Normal sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9.

Modular lines: every set of three sequential digits along a modular line must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}. Since all modular lines in this puzzle are on thermos, digits may not repeat along the modular lines.

Thermometers: Digits on thermometers must increase from bulb to tip, not necessarily consecutively. Each thermometer is also a modular line running from bulb to tip. Thermometers extending from the same bulb are distinct modular lines; that is, modular lines do not necessarily cross over bulbs from one thermometer to the next.

A mix of German whispers and modular lines that will make your eyes go fuzzy as you try to keep track of which is which along the rows.

Estimated difficulty: 2.5/5

*Rules*

Normal sudoku rules apply: every row, column, and box must contain a complete set of the digits 1-9. *XV*: Digits separate by a V sum to 5. Digits separated by an X sum to 10. Not all possible or Vs are given (no negative constraint). *German whispers*: The green flag stripes starting in rows 4, 6, and 8 of the flagpole in column 1 are German whispers lines. Adjacent digits along these lines must differ by at least 5. *Modular lines*: The teal flag stripes starting in rows 5, 7, and 9 of the flagpole in column 1 are modular lines. Each set of three adjacent digits along these lines must contain one digit from each of the residues classes mod 3; that is, one digit from {147}, one digit from {258}, and one digit from {369}. The flagpole is a separate modular line.

What better constraint for a Bastille Day puzzle than fortress cells? We sent this in to Cracking the Cryptic on a whim and were delighted to have it featured on 14 July 2022.

Estimated difficulty: 2.5/5

*Rules*

Standard sudoku constraints: each row, column, and box must contain a complete set of the digits 1-9.

Fortress cells: shaded cells are fortress cells and must be larger than any orthogonally adjacent unshaded cell.

Standard thermometer constraint: digits on a thermometer must increase from bulb to tip.

Watch a solve of the puzzle by Mark Goodliffe on Cracking the Cryptic

This puzzle was initially published in the Modular Lines Competition Pack for Cracking the Cryptic. It is republished here with permission from CtC. The complete pack is available to CtC Patreon members.

Estimated difficulty: 2/5

*Rules*

Normal sudoku rules apply.

Modular lines: every set of three sequential digits along a line must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}. Digits may repeat on a line if allowed by other rules.

XV constraint: Digits separated by an X sum to 10. Digits separated by a V sum to 5. Not all possible X's or V's are necessarily shown.

This puzzle was initially published in the Modular Lines Competition Pack for Cracking the Cryptic. It is republished here with permission from CtC. The complete pack is available to CtC Patreon members.

Estimated difficulty: 3/5

*Rules*

Standard sudoku constraints: each row, column, and box must contain a complete set of the digits 1-9.

Modular Lines**:** Every set of three sequential digits along a line must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}. Digits may repeat on a line if allowed by other rules.

Kropki dots: The digits on either side of a peach dot are in a k:1 ratio, where k is a whole number to be determined by the solver. Different kropki dots may have different values of k.

This puzzle was initially started in response to a prompt in a Speed-Setting Contest. We had 77 minutes to set a complete puzzle in which one or more aspects of one or more constraints were not given. Our initial set was broken but this is the cleaned up version. This puzzle also appears in Indigestion Collection 2.

Estimated difficulty: 2.5/5

*Rules*

Standard sudoku constraints: each row, column, and box must contain a complete set of the digits 1-9.

Standard killer cages: Digits in a cage indicated by a dashed line cannot repeat and must sum to the total shown in the upper left corner of the cage. In this puzzle, not all cage totals are given.

Modular Lines**:** Every set of three sequential digits along a line must contain a complete set of residues modulo 3, i.e. one digit from {1,4,7}, one from {2,5,8}, and one from {3,6,9}. Digits may repeat on a line if allowed by other rules.

Kropki dots: The digits on either side of a peach dot are in a k:1 ratio, where k is a whole number to be determined by the solver. Different kropki dots may have different values of k.

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