Simple, calming, head scratching and challenging. Four words that shouldn't have much in common but one game matches all of those terms: Puzzle Restorer.
Players are tasked with the role of restoring old works of art. These works of arts have been damaged in a way that means, frequently, the outline remains but nothing else. Players must fill these gaps in by drawing lines across them all. It sounds simple, because it is, but there are a couple of catches. For one thing, players are limited in the number of strokes that can be used and these strokes are quite rigid in how they can be moved. Only so many squares can be filled in too, meaning it's vital to not overlap too much. They can only paint a line that starts and ends with the color they want to use, too. Such simple stipulations can quickly turn this puzzle game into quite the challenge.
At first, Puzzle Restorer is quite easy to run through. The first couple of levels teach the basics in a way that the tutorial struggles to fully communicate. This sense of ease doesn't last long, though, as the presence of challenges such as the need to mix colors arise. The mixing itself is simple enough with red and yellow making orange and so forth. Trying to get things lined up correctly is the tricky part, especially with some more expressive paintings.
Puzzle Restorer does a good job of keeping the player interested though. Relaxing music and a convenient undo button maintains the interest, although a lack of a full scale example of how the image should look does make things harder and slightly unfairly so.
Despite such flaws, Puzzle Restorer is still well worth its $0.99 price tag. With 64 levels, plus a series of secret stages, it's going to take a while to finish the game but it'll be good fun getting there.