Puzzle No. 521: Cross The Streams

Edit: I posted the wrong version. Apologies. Corrected now.

Yay, a big puzzle!

Rules: Shade some empty cells black to create a single group of black cells that are all connected to each other through their edges. No 2×2 cell area within the grid contains all black cells. Numbers to the left/top of the grid represent the groups of consecutive black cells which are in that row/column in order, either from left to right or from top to bottom. For example, a clue of “3” means the row or column has three consecutive black cells, and a clue of “3 1” means that the row or column has a group of three consecutive black cells followed by a single black cell, separated by at least one white cell. A question mark (?) represents a group of consecutive black cells whose size is unknown; an asterisk (*) represents any number of unknown groups of black cells, including none at all.


Penpa link: https://git.io/JEEke


Puzzle No. 520: Country Road

I have a lot of pending things to get to, which I hopefully do by the end of the month, including some more elaborate blog posts.

For now though, this is a puzzle.


Draw a non-intersecting loop through the centers of some cells which passes through each region exactly once. A number in a region represents how many cells in the region are visited by the loop. Orthogonally adjacent cells across a region border may not both be unused. The black cell just means it’s a hollow, I.e., not part of the grid.

Penpa: https://git.io/J0jfE

Puzzle No. 517-519: Nikoli! (Tribute to Maki Kaji)

I haven’t posted in a while. There are a bunch of reasons for this, including travel and a bad reaction to my first vaccine dose.

Anyway, today’s post is a tribute to Maki Kaji, who passed away last week from cancer. I was going to elaborate on my thoughts more, but honestly this post by Thomas pretty much says exactly what I wanted to, perhaps in a better way.

I got into Nikoli.com pretty late, and just had a year of solving before the online solving portion had to close. I do purchase their books from time to time and I absolutely love the giants series.

Like Thomas, my note of thanks will be for his broader contribution to the puzzle community via Nikoli, influencing me and so many other puzzlers positively.

As a tribute, I have written 3 Nikoli style puzzles, and by that I mean ‘Nikoli style’ – I’ve tried to keep look, difficulty and dimensions as I remember them from Nikoli.com.



  1. Place light bulbs (circles) according to the following rules.
  2. Light bulbs may be placed in any of the white squares, the number in the square shows how many light bulbs are next to it, vertically and horizontally.
  3. Each light bulb illuminates from bulb to black square or outer frame in its row and column.
  4. Every white square must be illuminated and a light bulb can not illuminate another light bulb.


  1. Place black “triangles in squares” (see 2) in the grid under the following rules.
  2. There are four kinds of black triangles you can put in the squares (shown below)
    . You cannot place black triangles in the black squares.
  3. The parts of the grid that remain white (uncovered by black triangles) always form a rectangle or a square.
  4. The numbers indicate how many black triangles are around it, vertically and horizontally.


  1. A rectangle, bordered by bold lines, is called a “room”. Fill in cells under the following rules.
  2. The numbers indicate how many painted cells there are in a room. Rooms with no number may have any number of painted cells.
  3. White cells cannot stretch across more than two rooms in a straight line.
  4. Painted cells cannot be connected horizontally or vertically. White cells must not be separated by painted cells.

Rule credits: https://www.nikoli.co.jp/en/puzzles/index.html

Penpa links

P517: https://git.io/J0aKg

P518: https://git.io/J0aP0

P519: https://git.io/J0a1f

Puzzle No. 514-516: Tapa, Tapa [Palindrome], Tapa

I got a bit late when it comes to keeping my alternate day schedule so here are 3 puzzles to make up for it.

Only the last one is “fresh”. The first one is a bit silly but also probably nice, I was experimenting with an idea, some people on discord have seen it already. The second one, the variant, is from a speedsetting contest quite a while ago. We had an hour to construct a Palindrome variant. This one took me about 35 minutes if I recall correctly. The third one is just a vanilla Tapa.

Tapa Rules: Shade some empty cells to create a single connected wall. Numbers in a cell indicate the length of consecutive shaded blocks in the neighboring cells. If there is more than one number in a cell, then there must be at least one unshaded cell between the shaded cell groups. Cells with numbers cannot be shaded, and the shaded cells cannot form a 2×2 square anywhere in the grid.

Palindrome variant additional rules: There are one or more palindrome lines drawn in the grid. The pattern of shaded and unshaded squares will be the same when read from either end of a line.

Links to solve each one:

Puzzle 514https://git.io/JR6hN

Puzzle 515https://git.io/JR6hH

Puzzle 516https://git.io/JR6hj

Puzzle 514:

Puzzle 515:

Puzzle 516:

Puzzle No. 513: Shakashaka

Lets start with an unrelated self-plug – https://www.gmpuzzles.com/blog/2021/08/japanese-sums-by-prasanna-seshadri/ Check this out!

Now to today’s puzzle. This is a “fresh” puzzle, i.e. only 2 or 3 people have seen it before.

Rules – Shade a right triangle in some empty cells, each of which occupies exactly half the cell it’s in. Each unshaded area must be rectangular in shape. A number in a cell represents how many of the (up to) four cells orthogonally adjacent to the clue contain triangles.

Penpa link to solve: https://git.io/JRCdn (Click+drag slightly to a corner to draw in that corner’s triangle, just click for dot)

Puzzle No. 512: Kurotto

Since I’ve just been back here recently, I should note that sometimes, I won’t be posting “fresh” puzzles. Mostly this is because I also want to use the blog to organize some of these puzzles better.

I have been participating in “speedsetting” contests lately over on the CTC discord server. I’ve seen that this may seem unappealing to some more experienced puzzlemakers, but honestly, its a lot of fun. Also, mostly it allows me to put together something without overthinking about “where will it get published” and “what are the requirements”, while being in a limited time setting that makes me “feel” like I am doing something different.

What about the quality of the puzzle then? I’ll let you be the judge, with today’s puzzle, which is from a speedsetting event that took place just 6 or 7 hours ago. The constraints given were to construct a Kurotto with the only clues being in sets of 3 orthogonally connected cells, of the same shape (allowing for rotations and reflections). Basically, either a puzzle with only L trimino sets of clues or a puzzle with only I trimino sets of clues. The time given was 40 minutes but I forgot about it and joined late. Fortunately, its Kurotto, probably as comfortable for me as Tapa, so I could whip this up in 5-6 minutes. It won 2nd place!

I have more puzzles from earlier speedsetting contests that I’ll be posting in the future, but for now, here is the Kurotto!

Rules: Shade some cells so that each circled number represents the total count of shaded cells in connected groups sharing an edge with that number. Cells with circles cannot be shaded.

Link to solve on Penpa: https://git.io/JRqze

Puzzle No. 511: Arrow + Between 1 & 9 Sudoku

I want to call the variant a lot of people now know as “Sandwich” by what it used to be called, including in past posts on this very blog. This is a puzzle I’d worked on a while back, for a speedsetting contest that I was too late to submit to.

In other news, the WPF Sudoku Grand Prix final results are here – https://gp.worldpuzzle.org/content/wpf-gp-sudoku-results-2021

There could be a minor change or two since the round 8 results are still “preliminary” but I’m confident that my final placement won’t change. So I’m 6th! Considering I started the year targeting a top 10 finish, I’m pretty happy with this. I had a really strong finish in the last 2 rounds.

What else.. oh ya, I just wanted to note that this is the vague schedule I’ll be going for (every alternate day). I’ll branch out on topics as I go I think.

Rules –

Insert a digit from 1 to 9 into each cell so that no digit repeats in any row, column, or bold region.

Additionally, the number in a circle is the sum of the digits which are covered by its arrow. Digits may repeat along arrows.

Also, the clues outside the grid are the sum of the numbers that are between the digits 1 and 9 in that row or column.

Penpa link to solve: https://git.io/JBj0a (You can tab with surface and Sudoku, the answer check is just for correct digits)

Puzzle No. 510: Akari

So… I’m back.

I wondered what I could possibly say along with starting to post here after such a long hiatus (from here anyway).

I do plan to start posting here regularly again though. Why? I guess we may or may not find out.

So after a lot of thought on what to post as my return puzzle, I decided, I just want to keep things simple.

So here’s a vanilla Akari.


Place lights in some cells so that every cell is illuminated. Lights illuminate the cell they’re in as well as all cells seen in a straight line horizontally or vertically, not obstructed by a black cell. Lights may not illuminate each other. Clues represent the number of lights in the (up to) four cells surrounding the clue.

We have penpa links now! Why penpa over some other platforms for this blog? I’ll probably write about that in a future post. I’ll also write about someone doing some nice work to make links out of some of the older puzzles of this blog. All that and more to come. For now, link to solve: https://git.io/JBSYU

The link is set to composite mode specialized towards solving Akari, and drawing in the bulbs correctly will trigger the answer check.

Puzzle Ramayan – Loops


If there are some very very patient individuals who still keep tabs on this blog (and thanks for sticking around), I do plan to make it active again. This doesn’t necessarily mean I’ll start posting puzzles (I have too many other places to submit to these days), but there are some long overdue recaps for WSC-WPC 2015 which I plan to do, after which I’ll also review other contests which happen.

However, I expect all of this to happen only from April. The reason for this is I fell significantly behind schedule with my projects in 2015 for many different reasons, and I’ve been making ground in 2016 to get back to a position where I’m up to date with everything I’m doing. I estimate this to happen by the end of March, after which I’ll have more time for recaps and reviews.

The reason I’m posting this, other than acting as a random update, is to notify the readers about a Puzzle Contest happening this weekend on LMI. Its the 7th round of the ongoing series, Puzzle Ramayan. It is based on Loop puzzles, authored by me. We’ve targeted this tournament for newcomers and beginners, so in this round I’ve spent some time on the Instruction booklet and experimented with providing steps for solving the types appearing on the contest. We’re constantly looking at ways to encourage new solvers to participate, so if you’re new to puzzles and think this is a good way, let us know, by participating! 😉

Contest Submission page with Instruction booklet – http://logicmastersindia.com/PR/201602/

Forum discussion – http://logicmastersindia.com/forum/forums/thread-view.asp?tid=1236

F.A.Q. – http://logicmastersindia.com/forum/forums/thread-view.asp?tid=381

I hope everyone participates and enjoys the contest!



Puzzle No. 509: Triomino Sudoku [Daily League]

I’ve got wayyy too much to do these days, so I’ve pretty much stopped any regularity on this blog. I might make the rare post though, like this one. I was a little bored of work and had some time so quickly explored this variant that’s part of the Indian Sudoku Championship which will be held online on LMI in about 13.5 hours. This one is pretty difficult (as are all variants I randomly and quickly post here when bored), but has some nice steps to get started.

Remember that you can solve the puzzles from the League online on the Sudokucup Guest League page with a 24h delay (though I’m not yet sure if this one can be supported there, but take a leap of faith, maybe it will be!).

Rules – Place a digit from 1 to 6 into each empty cell or blacken the cell so that each digit appears exactly once in every row, column, and outlined 3×3 region along with three black(shaded) cells. Each black(shaded) cell should be part of an orthogonally connected group of three blackened(shaded) cells (a triomino). No two triominoes can share an edge.