iPhone sudoku follow-up: ACTSudoku

2008-07-29 23:29:13 -08:00

A couple of weeks ago, I posted a list of requirements for an iPhone sudoku app. At the time, no app satisfied all of the requirements, but one did come close.

Pierre Bernard of Houdah Software posted a comment that his sudoku app, ACTSudoku, satisfied all but one of the requirements I listed. The only one remaining was rotational symmetry, which he asked about.

In response to our dialog on that post, he added rotational symmetry in ACTSudoku 1.1, which Apple has now approved. You can download it now for $2.99 USD (or free if you bought one of the earlier versions).

UPDATE 2008-08-01: As of yesterday, there’s now a free version of ACTSudoku, which only generates easy puzzles. This is good if you’d like to try it for yourself, but you don’t want to spend $3 just yet.

The interface is simple enough:

ACTSudoku's interface is a sudoku grid on a wooden background, with the difficulty below it on the left and the timer below it on the right. At the bottom is a toolbar with three items: A + button, an Info button, and an X button.

Notice that there’s no row of numbers for input. The obvious thing to try is tap on a cell, and it works:

Tapping on a cell brings up a square pop-up containing nine numerals, possibly colored by pencil-marks.

In other words, the interface is obviously postfix. The key word there is “obviously”: One of my requirements was that it must be obvious how to input numbers.

The input method is not perfectly obvious, however. One thing that stumps a lot of people (going by Bernard’s response to some iTunes reviews) is the fact that simply tapping on a number in the pop-up enters a pencil-mark, rather than locking in the number. You must hold down briefly to set a number in the cell. In the comments on the previous post, I suggested swapping these behaviors; I maintain that suggestion. (UPDATE 2008-10-29: ACTSudoku 1.5 added a preference to do this. It does, indeed, make a tremendous difference in the app’s usability.)

You may be wondering what all the green dots are. Those are pencil-marks, filled in automatically by the game. This is optional; you can turn it off in the settings, if you want to be completely free to make mistakes.

ACTSudoku's settings are in the Settings app; the only control there, as of 1.1, is a light-switch controlling the automatic pencil-marks.

With the automatic pencil-marks turned on, the game will not let you enter a wrong number. With them turned off, the game will let you enter a wrong number. Either way, you can clear the cell by tapping again on the cell and holding down on the giant number.

If you tap on a cell with a number filled in, the pop-up has only that number, and it fills the entire size of the pop-up. Holding down on it clears the cell (and, if automatic pencil-marks are turned on, restores the marks). In this screenshot, the cell has a 4 filled in.
Hold down on that giant 4 to clear it from the cell.

Of course, ACTSudoku is not perfect. It has some minor problems:

  • The interface confusion that I noted above. A long tap sets the number, whereas a short tap sets a pencil-mark. This arrangement makes no sense with automatic pencil-marks turned on—and they’re on by default. It would make much more sense to have the tap lengths the other way around.
  • The northern, eastern, southern, and western blocks are have dimmed-looking gray backgrounds, for no apparent reason. This is slightly distracting (but not enough to qualify as “garish”). I would prefer if all the blocks were uniform white.
  • I’d like to be able to turn off the timer. Again, I find this distracting.

However, it satisfies all of my requirements, so I declare ACTSudoku the winner of the iPhone sudoku race. Congratulations to Houdah Software!

12 Responses to “iPhone sudoku follow-up: ACTSudoku”

  1. Pierre Bernard Says:

    Hi Peter!

    Thanks a bunch for both the review on the blog and iTunes.

    Feedback is always welcome. Keep it coming. I have already started working on the next version. User feedback is usually a major factor when taking future directions.

    Pierre Bernard
    Houdah Software s.à r.l.

  2. efaith Says:

    I’ve been playing and encountered a few puzzles with non-unique solutions. I mentioned my experience at the forum and provided a photograph showing an example. I like this application quite a bit and I really hope they can fix this. I’m not really all that put off by it, but looking at the comments for Satori Sudoku back when they had the same problem, apparently a lot of gamers are. I’m surprised, actually, that Peter didn’t include it among his criteria. So, technically, even with this problem, ActSudoku satisfies all Peter’s criteria as is.

    One thing I really like about this game is that it allows savegames – multiple savegames no less, saving the puzzle and your state of play. You can apparently do this for more than one puzzle and for the same puzzle multiple times. This is useful for a variety of reasons – for example, you might be stuck and want to try another puzzle for now but want to save your current game so you can try again later. Or, something else that often comes up, the logic of the remaining squares can be highly indirect (it might take, say, ten steps before you arrive at a logical contradiction), and in these cases it is useful to try the board one way, and then try it another way, to see where the logic leads. With other iPhone puzzles I found myself working it out on actual paper because they didn’t provide any facility for testing possible solutions. But with ActSudoku you can save your game, then play it through one way, and then reload the game and play it through another way. This is actually how I was able to generate the alternative endings that I photographed.

  3. Peter Hosey Says:

    efaith: I’ve never used sudoku software much, so multiple solutions has not been a problem for me since I wrote my own generator (which I long ago abandoned, for this and other reasons). I’d been playing the Medium puzzles from the Daily Sudoku on paper on a small clipboard.

    So that’s why it wasn’t on my list of requirements: I hadn’t had that problem in years, so it wasn’t on my radar. Sorry for omitting it; it definitely is a requirement.

    Also, I don’t have much time for sudoku anymore, so I’ve only played ACTSudoku lightly (enough to assemble a review of its features); moreover, I’ve been playing on Easy (next time will probably be Medium). As such, I haven’t encountered this problem; otherwise, I’d surely have mentioned it.

  4. Pierre Bernard Says:

    I agree with efaith that non-unique solutions are definitely a major issue. I will work to fix that ASAP and release another update.

    Pierre Bernard
    Houdah Software s.à r.l.

  5. efaith Says:

    wow – quick responses from Peter and Pierre. If I were to guess, I would guess that there was no problem initially and it cropped up when ActSudoku switched to rotational symmetry. Picking the wrong squares to blank out can create non-uniqueness, and rotational symmetry is about which squares to blank out, so I see a possible relationship here.

  6. Pierre Bernard Says:

    Found the bug! It was a one letter typo in the “hidden pair in block” algorithm. This only affects a limited number of “hard” Sudoku puzzles.

    The fix will be submitted to Apple today.

    Pierre Bernard
    Houdah Software s.à r.l.

  7. efaith Says:

    That’s great! Thanks. I have the fixed one now.

  8. Pierre Bernard Says:

    Hi Peter!

    ACTSudoku has just received a major update. The most important addition are smart hints.

    I hope you will like it!

    Pierre Bernard
    Houdah Software s.à r.l.

  9. Pierre Bernard Says:

    The free version is back! It is now named ACTSudoku EASY and shares the exact feature set of ACTSudoku UNLIMITED. The only difference being that the UNLIMITED version adds “medium” and “hard” games.

  10. Pierre Bernard Says:

    ACTSudoku is now available for FREE:

  11. Peter Hosey Says:

    Is that the full version? If it is, and if that’s a permanent change, you should strike the word “FREE” from its name; otherwise, it looks like a light version.

  12. Pierre Bernard Says:

    Just noticed that the latest release of ACTSudoku addresses yet another of your concerns. The game board now has a uniform color.

    Regarding your above question: The FREE version WAS a full version. It differed from the regular version in that it showed ads. As of now, that version is no longer distributed. It just might return some day.

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