You should have two choices at the waterfall. You should come out of a door and see the waterfall. In fact, there is another door that is symmetrical to the one that comes out. This level is the last level. I found a task prop in a small room in the library. (Later, you can use this prop to revive some previous gyroscopes). Wait, you won't see the fire corridor on the third floor. You are wrong. Level 3 should not be able to play gyro. Besides, (it won't be in the ice and snow) enter the hall, enter the corridor from the door on the left side of the hall, enter the door on the upper left side of the map (the door closest to you in the U-shaped corridor), destroy a few puppets, then come to the second floor of the hall from the spiral staircase, use grab all the way to the second floor of the hall, bypass the waterfall outside the castle from here (stuck here), enter the door on the other side of the symmetrical plane and bypass the other side of the second floor of the hall to attack the plane.