In Which I Review Puzzle Apps #1: Shirodoko

I was browsing /r/puzzles when I saw a post by someone, stating that en had created a Kurodoko-related app called Shirodoko. For those of us who clicked the link above and are about to complain that I've linked you to an article about Kuromasu instead, they are the same thing.

Now, the first thing that ticked me off was the name. For those of us not in the know, "Kurodoko" is often translated as "Where Is Black Cells?", so Shirodoko would be "Where Is White Cells?". I was rather annoyed, therefore, to notice that in none of the screenshots for the game were there any white shaded cells.

I also saw that in one of the screenshots, there were differently-coloured cells instead of a sea of black (or white) cells. "Oh no," thought I to myself, "Perhaps this is a 12-year-old who firmly believes that en's design choices are brilliant." The reason this is a problem is because it looks annoying, takes up more code, and serves no purpose. You don't need to put it in your code. Take it out so that the game will run faster on slow devices (like BlueStacks App Player).

But still, perhaps the screenshots were merely not representative of the game as a whole. So I downloaded it. After all, it was free.

I opened it up and discovered that it was connected to Google Play Game Services. The authorization screen for Google Play Game Services is extremely annoying. If possible, I would suggest to turn off the requirements of it wanting to know who's in my circles, and turn off the ability to post to my page.

The first thing I looked for when playing it was an option to turn off coloured squares. It was THERE that I found an option to turn the squares white as well. So that mystery's solved then.

The app's page said ""Translated" in over 30 languages. The language option in the app, though, only allows switching between English, French, and Spanish. Celui qui a créé cette application est un sale menteur. Én probablemente debe tomar un momento para pensar en sus palabras.

I wanted to see how well the creator had entered the rules. En had done so very well (besides the use of "coloured" instead of "shaded"). Then I checked the tutorial.

Here is a sample screen from the tutorial. (Did I forget to mention that this app is ad-supported? Because it is.)

The app says that the 9 and 10 at the bottom are both already solved, and that the 11 and 12 are solved because of this.

However, there are no black dots at R6C9, R7C9, R8C5, R8C6, and R8C9, which implies that some of those squares COULD be shaded. Therefore, the tutorial is contradictory and/or inconsistent.

Not only that; there is more than one solution to the tutorial problem.

I can forgive the fact that there were coloured blocks. I can forgive the screenshots not reflecting the title. I can forgive the Google Play Game Services screen, and all of the tiny little bugs, inconsistencies, and bad UI choices (why on earth would you not program the "tap twice to pencil-mark a square" option instead?!) that annoy me.

But this is an abomination. Logic puzzles should only have ONE solution, or else they cannot be solved using logic! It doesn't matter if they can all be accepted as a correct answer, the fact is that there is no longer a fully logical path to the solution, and that one is required to guess somewhere! Puzzlemaster Grant Fikes stated it well (you should probably read the comments, too): "How am I, as a logic puzzle connoisseur who wishes to keep his blog PG-rated, supposed to respond to such an atrocity? There is no appropriate invective-free response to this kind of horror. You simply do not bill something as a logic puzzle with only one solution, and have it actually have multiple solutions."

This is why I have subtracted 10 points from its original rating. Please, take your app back to the drawing board, and don't return until each puzzle has exactly one solution.


Verdict: -8/5. Do not get this app until it has updated accordingly.

(Note: if you would like me to review your Android puzzle app, please contact me at the email found in the About page.)


  1. Thanks for the review! Just so you know it is translated in over 30 languages, it just allows you to choose 3 currently depending on what region is detected. I didn't bother implementing a full language picker.

    And I decided midway through the project to have the colored squares the default, hence the name. I wanted the name to be vaguely like sudoku. In China the app is called Shidu (试独). Sudoku in Chinese is Shudu (数独).

    Lastly this game can have multiple solutions for a given game board, that's normal! It is rare for it to be a tile where it affects a number. So it's perfectly fine that the tile you circled could be both colored or uncolored.

    See the top of page 7 on this document if you don't believe me about multiple solutions!

    1. The problem with marketing this as a logic puzzle is that well-constructed logic puzzles have only one solution, whereas the puzzles in your app do not. That particular paper talks about general logic puzzles, not well-constructed logic puzzles.

      In any case, I do not consider the strategy at the top of page 7 to be a valid one, as it is dependent on the fact that each puzzle only has a unique solution. If the puzzle did have a unique solution, then one could deduce that those cells would be white by a different method; e.g. showing that a neighbouring cell were black, or that it would be required for connectivity.

      Also, you may say it is "rare" for it to be a tile that affects a number, but on my very first level, I bumped into such a situation. I should have taken a screenshot, but I'm not about to go diving back into this mess to prove to you that you really should fix this. Many people have commented on the linked Grant Fikes review detailing ways to fix this, so you may as well do so in order to stick with your claim that it is a logic puzzle and not a guessing game.

      Finally, I am Chinese, so I am fully aware that the translation for "试独" is "Test Is Alone", which doesn't make much sense with regards to the game.

  2. Forgot to mention, in Japan and Korea the game is called IRODOKO :)

  3. In my old age, I've had a harder and harder time ripping apart apps like I did in the days of yore, because I guess I appreciate that these apps are these people's babies, and I assume that someone might be more interested than I am. But I downloaded the iPad version, and disliked it. The colored squares don't annoy me, for some reason, but they are unnecessary, as you pointed out, and would annoy many pencil-and-paper solvers. The tutorial didn't teach how to actually use the app, merely how the puzzles work; it took forever to figure out that the pencil icon is how you make dots. Also, Simon Tatham's Javascript app ( generates puzzles that are more challenging, have unique solutions, and have symmetrical givens.

    The app's maker wanted me to review it. He wrote the following:

    Hopefully unlike a big fan of yours ( ) you can get over the nonsensical names I picked for my app. It's called IRODOKO in Japan/Korea and 试独 in China. His other criticism was blaming me for puzzles having more than one solution, even quoting your review corner volume 2, when you take someone to task who wrongly said a puzzle has one only solution. I never claimed there was only one but I still got an eyeful of those same words of yours :)

    I'm sure you understand the concept of multiple solutions better than your fan, of don't care cells in Karnaugh maps and that a NP-hard problem such as kuromasu makes it impractical to make an algorithm to create "better" games. Puzzle crafting masters such as yourself fill this gap better.

    So please review my app, even if you lay it on me for going with puzzle quantity over quality.

    I have no quibbles with the app's name whatsoever. I do have qualms about the multiple solutions thing, given that Tatham's app easily generates puzzles with unique solutions, and something that's supposed to be the next Sudoku should have unique solutions. At least the app's creator didn't have the audacity to claim the solutions are unique in the description, thereby telling a blatant lie. I don't know what a Karnaugh map is, although I could probably Google it to find out.

    When I review an app with computer-generated puzzles, I try to keep an open mind and focus on whether the interface facilitates a fun solving experience or not. My reviews of a few Everett Kaser games, for example, were positive. But I'd rather use the Conceptis apps than this one, for whatever reason.

    1. The notification email I got from you commenting on my post appearing in my inbox gave me a shock this morning.

      I think the most annoying thing about this interface is the fact that one has to click a separate button to switch from placing black cells to white cells, thus requiring one to move their fingers more (or in my case, my whole mouse). The better design choice, of course, would be "tap once for white, twice for black" or vice versa (like Conceptis). Even if all the other bugs were fixed, and each puzzle had only a unique solution, it would still only be 3.5/5 purely because of this design choice.

      My issue is with the words "logic puzzle" in the app's description. I would think that the fact that it's described a logic puzzle would instantly imply that it has a unique solution, or that (at least) the creator of the game has tried to make each level have a unique solution (and may have slipped up somewhere). I still go by your old opinion, then, that logic puzzles with non-unique solutions are not solvable, and therefore are bad.