Requirements for a proper iPhone sudoku app

2008-07-12 14:05:38 -08:00

  • A sudoku generator. The game should not cap me at x-hundred or x-thousand puzzles. Give me all the sudoku the iPhone OS’ PRNG can create for me.

  • Proper sudoku puzzles, not Number Place puzzles. The difference is that a sudoku puzzle is rotationally symmetric: if you turn the puzzle 180°, it still looks the same.

    Starting with a proper sudoku puzzle, → 180° → rotation gets you the same layout of starting numbers.

    Many sudoku generators actually generate Number Place puzzles, which don’t have this constraint. (In particular, all the Will Shortz puzzles are like this.)

  • Obvious input method. A row of numbers at the bottom doesn’t work because I can’t tell whether the game is prefix (tap number first, then cell) or postfix (tap cell first, then number). I could get used to either way, but a good interface doesn’t make me guess.

    • Ambrosia’s Mr. Sudoku uses handwriting recognition.

    • Platinum Sudoku is clearly postfix, because its input method is a ring of numbers around whatever cell you tap on.

  • The ability to set pencilmarks, to keep track of what numbers are viable for a cell (helping to avoid wrong numbers, especially at higher difficulty levels).

  • Simple, usable interface. This means two things:

    • No excessive artwork like Big Bang Sudoku has. I only have 16 GB of flash memory—don’t waste it!

    • No garish colors. If your sudoku game is in CGA, then I don’t want to look at it, which means I don’t want to play it, which means I don’t want to buy it.

17 Responses to “Requirements for a proper iPhone sudoku app”

  1. Grady Haynes Says:

    Wow, CGA.

    Big Bang Sudoku doesn’t look too heavy to me: the Platinum Sudoku you also listed is 52 MB, though, nearly 19 times bigger! Still, just the size of an album. I don’t mind that for a great app, but 100 MB is pushing it.

    What if the tiles are at the bottom and you drag them? That avoids the prefix/postfix problem and seems far more iPhone-appropriate / non-modal than prefix, postfix, or handwriting. Advanced Tile Sudoku does that, is only 1.5 MB, and is more visually appealing to me than the others you listed. iTunes link:

    I haven’t played any of these (the one I linked has 5 stars; just 3 reviews), not much of a Sudoku player, just interested in UI design and convention on this new platform.

  2. Patrick Burleson Says:

    I’ve been enjoying EA’s SUDOKU:

    It looks great, has good sound effects. The only thing I think might annoy you is needing to tap the space to enter the number. It’s small at 6.6 MB ( I bought and downloaded it over EDGE ) and keeps statistics (i.e. average time, best time, etc )

    I also don’t quite understand the 180 degree thing. Is that on initial placement of the “given” numbers?

  3. Pierre Bernard Says:


    I am the author of Houdah Software’s ACTSudoku for iPhone. I believe you are going to love it.

    1. A sudoku generator: CHECK: virtually unlimited fresh games, not plain transformations applied to existing boards
    2. ACTSudoku generates symetrical puzzles. They are symetrical along one axis: horizontal, vertical or diagonal
    3. Obvious input method: Watch the screencast at I think you’ll like it
    4. The ability to set pencilmarks: CHECK: ACTSudoku calls them markers. OPTIONALLY, ACTSudoku may help you by automatically blocking excluded values. Great at higher difficulty levels
    5. Simple, usable interface: Matter of taste. I say CHECK

    Pierre Bernard
    Houdah Software s.à r.l.

  4. Peter Hosey Says:

    Grady: I’ve seen Advanced Tile Sudoku. The dragging idea is intriguing, and though a row of numbers is non-obvious no matter what you do with them, at least the product page tells you up front.

    It’s also one of the few that generates rotationally-symmetric puzzles.

    Patrick: Postfix doesn’t bother me. I prefer it, actually. I like RPN, too. ☺

    Yes, rotational symmetry applies to the given numbers. Those are the black cells in the diagram.

    Pierre: I did like ACTSudoku‘s input method (which I thought similar to the ring of numbers) based on the screenshot, but I’m more dubious after watching the screencast. It’s more complex than it looks. I suggest swapping number-placement and pencilmarks, so that changing the number color is what takes the longer tap. That said, I’m willing to give it a shot the way it is.

    More importantly, ACTSudoku does not generate rotationally-symmetric puzzles. All other forms of symmetry don’t count.

  5. Pierre Bernard Says:


    The concept of rotational symetry is interesting. I’ll see I’ll add it as an option in an update.

    How come you like this so much? Are there any advantages to solving such a puzzle? Or is it just a matter of taste?

    Pierre Bernard
    Houdah Software s.à r.l.

  6. Peter Hosey Says:

    For me, yes, taste.

    Nikoli argues that this changes (they would say improves) the gameplay, and I don’t disagree with them. Of course, we should keep in mind that they sell their own sudoku, including one of your competitors. ☺

  7. Pierre Bernard Says:

    Hi Peter!

    I am about to wrap up development on an update to ACTSudoku.

    It adds rotational symmetry!
    It also adds a bookmarking feature as well as the ability to start over with a given game.
    The interface has also been fine-tunes.

    Did you get a chance to try ACTSudoku? I’d love to hear your feedback.

    P.S: Apple is currently very slow in pushing updated applications to the App Store. I have no idea when the new version will become available for sale. But it will be a free update.

    Pierre Bernard
    Houdah Software s.à r.l.

  8. Peter Hosey Says:

    I have not. Please post another comment when Apple approves the update; I shall download it then. ☺

  9. Pierre Bernard Says:

    I have just downloaded “Sudoku Unlimited”. Hey, got to see how the competition is doing!

    I am baffled how this can be so popular with customers. It falls short on my no. 1 criterion for a Sudoku game: the boards are not solvable by logic. They require guessing and backtracking. IMHO this is just unacceptable. Instead of a Sudoku generator, one buys a plain random number generator!

    P.S: ACTSudoku 1.1 is in the hands of Apple’s reviewers…

    Pierre Bernard
    Houdah Software s.à r.l.

  10. Pierre Bernard Says:

    Good news: ACTSudoku 1.1 is now available for sale at the iTunes App Store. It features symmetrical puzzles!

    Pierre Bernard
    Houdah Software s.à r.l.

  11. Peter Hosey Says:

    Pierre: I saw it and played a game even before your comment. Good work. ☺

  12. Pierre Bernard Says:

    Peter: If you like what you see, I’d appreciate if you could leave a review on the AppStore.

    ACTSudoku has been dragged down by negative comments. Most by people to dumb to read the description which tells them

    – to use long taps to commit a value
    – go to the Settings application to switch off negative markers

    Pierre Bernard
    Houdah Software s.à r.l.

  13. Peter Hosey Says:

    Pierre: Done.

    Thanks for all your effort. I posted a review of ACTSudoku here on my blog, as well (a few minutes before seeing your latest comment here, actually).

  14. Chris Says:

    Hi Peter,

    Have you had a look at Sudoku Grab? I put it on the app store a couple of weeks ago.

    I don’t know if it covers all your criteria – it doesn’t have a puzzle generator. What it does have is the ability to take a picture of a puzzle and then play it on your phone! It’s really cool (even if I do say so myself).

    The UI is pretty clean. I’ve just submitted a new update – should be live sometime next week that adds a lot of new features.

    The next updates will be all about improving the puzzle playing interface – I’ll definitely be using your criteria to drive that.


  15. Peter Hosey Says:

    Chris: That’s certainly nifty. Not too useful to me, though, as I have an iPod touch, so no camera. But for someone with an iPhone, that practically counts as infinite sudoku, since you can buy enough books and magazines and download enough online sudoku to set yourself up for life.

    I hope there’s a way to build up a cache of sudoku. For example, you could load an entire book of sudoku into the phone before a trip, in order to play the contents of the book while in transit.

    I would also suggest using the solver to check puzzles, if possible. At the least, it could only present the “please check the puzzle” screen if the solver can’t find a solution to the puzzle as initially scanned; even better would be if your recognizer can provide alternate numbers to try.

    The next updates will be all about improving the puzzle playing interface – I’ll definitely be using your criteria to drive that.


  16. David Ross Says:

    Hi Peter,

    Based on your criteria I think you’d enjoy checking out my newly released Uni Sudoku for the iPhone/iPod Touch. For several years I’ve sold a popular Mac application that is now an iPhone app. I believe the only criteria in your list not satisfied is unlimited puzzles. There are 100,000 in Uni Sudoku. First, I challenge you to complete that many, second I challenge you to remember puzzle 1 when it comes around again after 100,000.

    More seriously, by not including my puzzle generator in the iPhone app I’m able to make sure all of my puzzles satisfy my criteria for being interesting and appropriately rated. Finally I update the puzzles list when I submit a new update.

    If you do check it out I’d love to hear any feedback you have.


  17. David Ross Says:

    Correction: Uni Sudoku comes with 10,000 puzzles. I apologize for the error but the challenge stands. :)

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