Concretely, there are numbers around the gate for each row and column around the grid. They represent the number of boxes to be colored. For example if the line 4-2 indicates, we know that there will be in this line a set of 4 and a set of at least two, separated by at least one blank. When filling the grid, the image appears and numbers are barred to progressively to indicate that we are on track.
This is a puzzle game and clearly addictive logic. If the first levels are very easy to guide us, all thickens quickly. The game is divided into 9 levels each of which proposes a very different number of gates (8 to 48) is more than 300 in all grids; what you care for long, long hours ...
Note that the game is only in English and that the tutorial is not easy to get to if you do not master a few basics of the language even if you soon figure playing. The only flaw of the game is in these increasingly large screens (up to 50 boxes) that will force him to zoom in regularly to fill them. Even with a 10-inch tablet, it can not properly fill the boxes without the zoom (so I do imagine a smartphone with 3 inches!). This is clearly a handicap for very large screens, even if they are not systematic. This is not because we exchange level as the grids will all necessarily large. One of the puzzles of the hardest level for example, offers a minimalist grid (6 squares). More boxes can also be filled with a single finger swipe remaining press box and dragging the finger which prevents eg click 30 times when you have to fill 30 boxes of the same line.
In summary, a very good game if you like the genre. The biggest wasting a bit fun The only regret is the readability of the grids to play forcing zoom and lose the overview of the image to draw.