#6: Cracks on Glass (Sudoku variant)

I was really big on Sudoku-based puzzles back then, huh.

Rules

Classic 6x6 Sudoku rules apply. Additionally, connect pairs of orthogonally adjacent cells with straight lines between their centers, so that all cells form one connected network. Also:

• Cells with digits 1 and 2 should be directly connected to 1 neighbour each.
• Cells with digits 3 and 4 should be directly connected to 2 neighbours each.
• Cells with digits 5 and 6 should be directly connected to 3 neighbours each.

Here is an example of a valid grid with lines drawn in:

#5: Boxer (Tapa)

As far as I can tell this was the first non-variant puzzle I've set.

Classic Tapa rules.

Difficulty (select to make visible): ★★⯪☆☆

Solve in puzz.link

#4: Tring-Tring

This is my first genre that took off somewhat. It's an adaptation of the classic Nikoli's ring-ring for a hex grid, with triangles replacing rectangles. There's quite a bit of new interesting logic arising from this.

After sharing several puzzles at CtC server, I've discovered that Esther (echo) had previously created something very similar at the very same server. Subsequently, Pedro PSI has implemented this genre in his Kudamono project, as well as a few variants, and it's also been featured at PuzzleSquareJP.

UPD (2026/09/09): unfortunately since the time of this post, the Kudamono project died, and ultimately the website was taken over by scammers. For this reason the Kudamono links have been removed.

Puzzles below are the very first ones I've shared at CtC. They're all fairly challenging, and the genre itself is very tricky, so feel free to have a go at easier ones using links above.

Rules:

Draw lines between pairs of cells with common sides to form triangular loops. Each cell must be covered by some part of a loop.

Loops may intersect each other, as long as the intersection is not a corner of any loop. Loops may not overlap or share corners.

Here's a small example by Pedro:

Solve in Penpa

#3: Parity Falls (Sudoku variant)

My first full-size sudoku puzzle. Partially inspired by Parity Islands by yttrio.

The parity rule may take some time to figure out, and even then the logic isn't easy (but hopefully fair). Enjoy!

Rules

Classic Sudoku rules apply.

Each digit is orthogonally adjacent to at most one greater digit of the same parity as itself, and to at most one smaller digit of the same parity as itself. E.g. a 5 can't be adjacent to both a 7 and a 9, or two 3s, but can be adjacent to a 3 and a 7.

Difficulty (select to make visible): ★★★⯪☆

Solve in Penpa

Solve in SudokuPad

#2: Sudoku-Slitherlink hybrids

I'm a big fan of loop genres, and even more so when they are neatly combined with other rulesets. If one tries to combine Slitherlink with Sudoku, it's natural to treat digits as clues, but numbers 4 and larger quickly break the Slitherlink. Here's a pair of my attempts to make it work: a 4x4 that ignores the 4s, and a 6x6 with a "sheep and wolves" mechanic.

#1: Skyscrapers (Rooftops)

These are the very first puzzles I made, and shared at the Cracking the Cryptic Discord server. I'm still mostly happy with them.

To my knowledge this exact variation is novel, although similar rulesets had certainly been flirted with many times over.

I really wanted to make a sudoku with this ruleset, but that will have to wait for some other day.

Rules

Skyscrapers variation. Place a number from 1 to N in each cell (N being the size of the grid), without duplicates sharing a row or a column. Some numbers may already be given.

Number in each cell represents a building of the corresponding height located in this cell. Corner clues in cells specify the number of other cells visible "from the rooftop" of the building, looking in the four orthogonal directions. Buildings lower than your current height are not visible, and higher buildings block lower buildings behind them.

Formally, a cell y is visible from a cell x if:

• x and y are in the same row or column,
• y has higher number than x,
• there is no cell with a number higher than y between x and y.

First post

I created this blog primarily to document and share puzzles I made, starting in October 2023. There may be some other things I'd like to post occasionally, although algorithm- and competitive programming-related stuff is more likely to end up on Codeforces.