How to Solve a Picross Puzzle

Read on or skip to the video to brush up your picross skills.
 
 
The object of a picross puzzle is to darken all the correct squares in the grid to reveal a hidden image.

The numbers on the sides of each row and column represent continuous blocks of darkened cells. Note that every block of darkened cells must be seperated by at least one blank cell. (There may be many more than one blank cell between continuous filled squares, but there must be at least one.)

It’s also important to pay attention to the order the numbers are listed in. The order in which they’ll appear in the grid will match the order they are listed.

Start out by filling in cells for rows and columns with only one possible configuration of darkened cells. It is just as important to mark off the cells you know cannot be darkened as it is to color in the darkened cells. Marking blank cells with an x or a dot works well.

In this example, one blank space is needed to seperate the blocks of 3 in the center row, making the configuration of 3 dark, 1 blank, 3 dark the only possible sequence that will meet the requirement. In the same way the 1, 1, 1, 1 sequence must have at least 3 blank squares to keep the 4 single darkened cells seperate from one another.

picross puzzle, example 1, step 1

Next, fill in the squares you can logically deduce must be darkened for every possible configuration in that row or column. For example, the rows and columns with a block of 5 darkened squares in this picross must have their center 3 cells darkened because all possible placements for the block of 5 use these same 3 cells.

picross puzzle, example 1, step 2

As you darken cells, this will also reveal which cells must be empty. In this example, we know the cells with the bold orange x’s are empty for two reasons. First, the only darkened cell for each of the outermost rows and columns is identified, so we know no other cells in those rows and columns are darkend. Second, one of the cells in the block of 3 is identified. We know the most cells adjacent to this cell that could be darkend is 2, and the cells with bold orange x’s are 3 cells away from those cells.

picross puzzle, example 1, step 3

By the same token, as you rule out cells and mark them with an x, this will reveal more information on which cells must be darkened. In the example, all the remaining empty cells in the rows and columns with blocks of 5 must be darkened to allow the blocks to be a full 5 cells long.

picross puzzle, example 1, step 4

These strategies were enough to complete this simple puzzle.

picross puzzle, example 2, step 1

Let’s look at a different puzzle to demonstrate a couple of additional strategies. In this example, one row has a block of 7 darkened squares, since 7 is the full width of this grid, all the cells in that row will be darkened.

picross puzzle, example 2, step 2

Since we know the second cell from the bottom is darkened and the block of 5 in the center column must be continuous, we can count 5 up from the bottom of center column and darken all the cells from the second to the fifth cell in that column. The same technique can be used on the columns with blocks of 3.

picross puzzle, example 2, step 3

In the case of the column farthest to the right, we know all remaining cells will be blank, because we’ve identified the single darkened cell in that column. For the column to the far left, we know the cells below and above the single darkened cell must be blank becuase the lowest block in that column is 1 cell long. We know it cannot be the bottom-most cell becuse darkening that cell would make the last block in the column at least 2 cells long. We can also deduce with a previously mentioned technique 2 cells of the block of 3 in the left-most column.

picross puzzle, example 2, step 4

Any time we have a cell filled in on an edge of the grid (and sometimes when we have a cell immediately against another one we know must be blank), we can count out the full span of the block we know comes next in the sequence. In the case of the cells we have in the left-most column, we know the top one must be the first in a block of 2. We can fill in one cell and rule out the cell that comes after it. In the case of the lower cell, we know the first cell in this row is only 1 cell long, so we can rule out the cell immediately next to it.

picross puzzle, example 2, steps 5-7

Now we can employ techniques we’ve already used to keep darkening and ruling out cells in the grid until we reveal the full image.

And finally, this video will show you a few more advanced techniques (as well as a review of the basics).

These strategies should be enough to get you started solving picross puzzles on your own.  If there’s anything in the examples you find confusing, put your question in the comments below.

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This Post Has 3 Comments

  1. Arman Dezfuli-Arjomandi

    Hmm, this is pretty good, but I’m wondering if it could be explained more clearly with animated gifs or fewer words.

    I’ve been trying to figure out the right way to explain how to solve picross puzzles for my picross game (https://www.falcross.com) but every time I try, I fail to come up with something that seems concise enough to keep a mobile gamer’s attention.

    Specifically the wording around blank spaces or “grouped tiles” or “sequential pixels” is really hard to figure out how to distill. Any ideas?

    1. Heather Newton

      For our purposes, and since puzzle tutorials are not our main focus, we needed something quick and dirty that wouldn’t take a huge time investment to create.

      I can see how GIFs could be a good way to demonstrate these concepts. It’s worth a try if you are looking for a good teaching method.

      I could also see doing a step-wise led tutorial if you have an app platform to work with. I’m thinking maybe an arrow pointing at a good row/column to start with and a written message like “There are X cells you could fill in for this row/column using the ___ technique. Touch the cells that must be filled in.” Then, after they do that correctly, point to a new row/column, and repeat the process.

      For another example, if you go through the Puzzle Quest this post is meant to assist with, and you don’t solve Stop #3 or Stop #10 within 2 days, our system will deliver a hint sheet to you where you will see another method I’ve used to walk people through when they are feeling stuck.

      I’m unsure if you watched the video on this page, but I would say the language I naturally used as I was walking through it would be the best suggestion I personally could come up with as far as how to word things. Beyond that, I would say the Wikipedia article for Nonograms is a great place to look for “standardized” technique names.

      I personally have been working my way through the picross puzzles in an app called Picross Luna. If it’s not already on your radar, it would probably be useful to try it out as a bit of market research. I tried out your app as well (on iOS), and I saw both pluses and minuses in comparison. I like that yours has a timer and seems to give you a rating which you can try to beat. I also like that the filled in cells show up as multi-colors and that your pricing model seems to be in-app purchases of hints rather than display or video ads.

      As for minuses, I don’t like that if I accidentally touch a cell, the app assumes I have made a logic mistake, and there appears to be no way for me to un-fill a cell that I have touched while using the blocking-in tool (as opposed to the X tool). Picross Luna has a toggle setting that I have switched to “don’t warn me of mistakes” — which I highly prefer. Warnings of mistakes are irruptive to the meditative state I want to be in while doing these puzzles. The other thing Picross Luna does that I much prefer is filling in the Xs in a row or column for me once I have blocked out the correct number of filled cells. Because of my no-warnings setting, the app’s logic can even fill in Xs that might not be correct, but it has an ever-present Undo button, which I make frequent use of.

      I agree that it would be nice if picross puzzles could grow in popularity. I think it’s a good brain exercise, and it definitely works a different part of the brain than the much more ubiquitous Sudoku. I’ve had many people tell me that it appears a picross is unsolvable or that the only conceivable way to solve it is to guess (neither have been true). I think it takes patience and concentration to get the logical techniques required to stick in your mind and become easy to identify when working a picross. Both of these things seem to be a little hard to come by in today’s world. I think that’s part of the reason it’s taking a while for picross puzzles to become more popular.

      Much luck with your app! I hope you can get a lot of people using it.

  2. Casey

    I’m still really confused I did the tutorial and I can do that but any of the other puzzles I get confused on

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