Review: Senkai Puzzle for iPhone and iPad

Senkai Puzzle is a well presented puzzle game for iPhone and iPad which was originally released a couple of months ago. The first version left me a bit cold because after solving the puzzle for the first time, which isn't too difficult, it lacked a clear objective to motivate playing again. An update has just been released, and the game is now a lot more interesting, in a Spinpossible sort of way.

At its core, Senkai is another group theory, sequential movement puzzle. It is played on a 2x2 arrangement of cubes, and this is the start position:

A move consists in turning a pair of cubes around their common axis, like this:

Of course the goal is to return to the start position after shuffling.
The user interface is very well done and uses swipes to turn the cubes. An excellent detail is that you can move the cubes just a little, to see what's on the side faces, without actually making a move. You can do that also to see what's on the back face, but that's not needed because the back face is the same as the front face, except that one is white and the other is red. The solved state uses only the white faces.

The update which has just been released adds an introductory 2x1 puzzle, which is much simpler to solve:

As I said at the beginning of the review, the initial version of the game lacked a purpose: it just showed a counter of the number of moves made, without any objective to meet.
This is fixed now because a "belt" grading system has been added:

after shuffling the cubes, you are shown not only the number of moves you made, but also the optimal number of moves needed. As the table above (for the 2x1 puzzle) shows, you need to solve the puzzle with no more than 5 extra moves to earn an orange belt, and so on; solve it 30 times with the optimal number of moves, and you'll earn the black belt. The requirements for the 2x2 puzzle are more relaxed to account for the higher difficulty.

I don't know what the theoretical maximums are; it looks like the optimal solution usually requires 5-6 moves for the 2x1 puzzle and 8-10 moves for the 2x2 puzzle. This should mean that earning the black belt in 2x1 shouldn't be too difficult, while for 2x2 it will be a lot harder.

Well done to Grifia for implementing such a slick interface and for recognizing the shortcomings of their initial release and quickly addressing them.

Summary

Nontrivialness	★★★★☆
Logical Reasoning	★★★★☆
User Interface	★★★★☆
Presentation	★★★★★
Loading Time	★★★☆☆
Saves Partial Progress	✘
Status Bar	✘

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