One of the best *casual* puzzles I have ever played. Simple, fair, don't require much to enjoy. A perfect timewaster.
The reason why I call this Casual is because anyone who already played a hardcore puzzle knows that there is a lot of room in this game for traps, enemies, shuriken etc. The dev was very kind not to put any of that so that casual players can have fun too.
The one and only downside is the apparent lack of challenge for completionists (ex. Bonus levels), given that it is rather easy to acquire all medals in a single run. There could also be time limits, too - ninjas have to be fast, right? But then again, paint takes so much time to dry out it wouldn't make sense to paint fast.
This is not enough to pull stars, because the rest of the game more than makes up for it.