Check the circular object on top of the elevator door.
Tap on it and drag, You'll see 2 rings with 1 clear layer in the middle.
For every 1 clear layer that is equal to 1, so drag the 1 clear layer to number 1. Drag another one, you will see there are 2 clear layers, drag it to number two. Drag another one, still 2 clear layers put it on the number 2 on the other side. Drag again, 1 layer, put it on the other number one. Drag again, 3 clear layers, put it on top of number 2 (blank space on top). Drag again, now you have 4 clear layers. In the mean time put it on top of the 3 clear layers. Drag again, 3 layers, put it on the other side above number 2. Get your 4 clear layers and put it on top of the elevator.
Elevator opens. Welcome to level 28.
