Games that are this polished never feel quite long enough because you want to play them forever. They've released new levels in the past, which are worth the extra gameplay. We may want new levels, but we also want those levels to be unique and distinct enough from all of the levels that have come before it, so that's the tradeoff.
Apart from the obvious MC Escher influence, this game has simple characters with cryptic personalities. There's a subtle tendency to use white and black to demonstrate good and bad, but to get caught up in that would be missing the point. Not only is the dunce cap provocative and seems to lend itself to magic, but it also allows the silent princess and the crow to ultimately share the same silhouette.
You can feel that every scene was given a generous amount of care. Each scene has a deliberate awareness of its own space. Sliding objects on the screen uses the strum of instruments to provide brilliant audio cues. This level of interactive detail makes you feel smarter.
When you finally put this game down, you can pick it up later without having to relearn it again. Monument Valley doesn't ask a whole lot of the user. It works very seamlessly with your sense of wonder, and that contributes to the magic.
While the navigation between levels, some icons and parts of the gameplay are unexpected and confusing at first, the confusion manages to add to the mystique. The game encourages you to play around and explore the environment before the real gameplay even begins, and when you create an environment that people want to explore, your users become more forgiving, and you can afford to be less intuitive. The interaction with the movable game pieces feels natural, and the simple tap-to-move gameplay is delicate, in a sense.