This game has an amazing premise. The game has two platforming worlds on each of the two 3DS screens. Your character can only exist on one screen at a time, with the other screen having a ghost form, and pushing R switches which world your physical form is in. You switch instantly and you'll be bouncing between the two screens a lot due to the creative design that derives from the amazing premise. This change-up breathes new life into the platforming genre similar to how Vanquish had a gameplay premise that switched up the third person shooter genre.
When this game is good, it's phenomenal. When it is bad, it is intensely frustrating. For some reason they put in quite a lot of stages that are just memorization challenges. These stages take way more time than the fun stages and are not satisfying at all. There are also a few challenges that are just too demanding. There are some pixel perfect jumps required and the late game is intensely brutal.
And just one suggestion for the future with that switch mechanic: instead of having the character bounce between the top screen and bottom screen, why not keep the physical form on one of screens and switches the worlds with R instead? It would be a good option for the future anyway. I found myself getting mixed up at times, and I don't think that difficulty should derive from wrapping your head around the control.
So please EndGame, make a sequel but maybe re-evaluate some of your design choices.