I finally saw some demo of the gameplay.
Very novel and interesting mechanic. However, I think I can already see a potential fatal flaw...
Once you reach the top of the building, you are at the "near" complete mercy of the "random" guests/ghosts you will be given. Since it is not possible to see more than a few blocks ahead, you can be put into a situation that is unwinnable even if you have played a "perfect" game up until that point.
For scoring, I suspect that, as the levels get more difficult, you will need to stack up combos in order to get the required scores for the 3 stars. This can be done, for example, by having more than +3 ghost points per level. However, this stacking can easily go bad if you are given a string of unsuitable blocks. Again, because you have no controls of what is given to you, whatever clever strategy you are using can be easily ruined randomly.
This type of mixture of strategy and randomness is like Tetris. No matter how expert you may be as a player, you can still lose a level because you just got a bad run of blocks. This worries me a bit as, if the game is not "properly" tuned, the game can easily turn into a frustrating mess.