Large slimeblock staircase

This is a 15 block tall expandable hidden staircase that pops up out of the ground and can be retracted again. It mainly consists of a bunch of slime block flying machines and redstone activated stops. It is a bit slow (see times below) and does cause a little bit of lag but other wise works smoothly. The door used is the 4x4 flush door I previously designed (see link below) but without the built in staircase.

Thought behind build: cool base entrance

Opening time: ~23 seconds
Closing time: ~16 seconds


Minecraft Version: 1.11.2

http://www.planetminecraft.com/project/4x4-flush-piston-door-with-staircase/