Review: FlowDoku for iPhone and iPad

Just when you thought that Sudoku had been beaten to death, here comes FlowDoku by HapaFive Games, which turns the concept on its head to produce an excitingly original new puzzle.

To be clear, the only thing this game shares with Sudoku is the basic premise of placing symbols on a grid so that certain requirements are met on every row, column, and box. That's pretty much the end of similarities.

In Sudoku you have 9 different symbols, which must not be repeated; in FlowDoku, you have a smaller number of symbols, some of which must be repeated a given number of times.

The second rule is the stroke of genius: the symbols that appear multiple times in a box, must be next to each other.

This second rule makes the solving strategies very different from Sudoku, and allows for a great variety of logic deductions.

At the beginning of each puzzle you have a number of givens; it goes without saying that there is only one way to fill the grid following the rules. So e.g. you need to get from this:

To this:

As you can see, graphically the givens are only slightly different from the shapes that you enter yourself. I found this a bit confusing initially, but quickly got used to it.

I was particularly impressed by how carefully the user interface has been designed. The basic way to put a symbol in an empty cell is to tap it multiple times, which makes it cycles through the available shapes. This could get tiring quickly, especially with the circle which requires 3 taps, but there is a very clever alternative way: just drag from a symbol which is already on the grid and you'll duplicate it. Cells that already contain a symbol aren't affected, so you can e.g. drag a circle to the opposite side of the grid, if the cells you slide over are empty. This works very well once you get used to it, and reduces tapping to a minimum.

There's a total of over 700 puzzles in the game; 250 can be played for free, the others can be unlocked using several different kinds of in-app purchases, including a single one which unlocks everything.
The puzzles are split across 4 sizes, and for each size they are split in packs of varying difficulty.

The size of the grid affects the type and number of symbols you have to use. Note that the circles are special because even if you have to place more than one in a box, they don't need to be next to each other like the other symbols.

12x12 is a bit too crowded for the small iPhone screen, but the controls are precise enough and, if you need to, you can zoom in on every box by holding your finger on it.

The game is very well designed. Great attention was given to many detail: it saves partial progress on every puzzle, tracks statistics, has a good tutorial that introduces the rules interactively, explains wrong moves, and so on.

Worth mentioning is a novel "roll back" function which doesn't simply undo your last move, but all the moves until your first mistake. This is a brilliant idea for this kind of logic puzzle.

Included is also a strategy guide, explaining some of the logic deductions that can be used to solve the puzzles. I encourage you to find them by yourself, however; it's a lot more fun that way. The rules are so original that they require some deductions very different from anything you might be used to.

The only issue I had with the user interface is that scrolling the lists isn't as responsive as native iOS apps: it looks like the lists scroll slower than you move your finger. But this is a minor thing and doesn't detract from the puzzle solving fun.

This is clearly one of the best logic puzzles released this year. Don't miss it.

Summary

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

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