TL;DR - it's fun, unless you're doing the challenges it isn't that hard.
So I might have lied a little when I said it was simple. Often it is simple to beat the level, but if you want to earn three shurikens on each level you may find yourself playing any given level dozens of times on repeat.
But that of course is why I love this game. It is not the easiest plat-former, but it also is not really challenging until you're combing the speed and score aspect.
Because of that the "difficulty" of the specific challenge you set for yourself allows for a really nice curve. Finally, it is interesting to listen to (at first, of course all repetitive music gets old), and the large point globes that are hidden allow you to play through a level slowly and methodically to try to find where they are hidden.
That is a wonderful mechanic to get people to notice all the little aspects that have went into making this game.
If you like this sort of die, rinse, repeat games at all, you will like this one.