Hi, I solved with the guardians: it was enough press on the symbol as fast as possible and not to wait for it to go in the final location.
But I read that someone asked if it is a demo or not. No matter for me: it's a BORING game repeating itself and just tapping on the screen without any combo! I played God of War 3 just few days ago and I must say that Kroll is not at the same level at all! Even Onimusha 1 and 2, which were 2D games and not 3D, they were much better than Kroll.