Shell as Hard as Steel

You are an elevator repair technician sent out on a night shift to restore service to the elevator of the tallest office tower in the city. The task seems simple: calibrate the elevator, climb floor by floor and repair the traction system at the very top. But nothing inside the building adds up. Every floor sits at a different height and the official blueprints are useless. To keep climbing, you'll have to reconstruct each missing measurement from the clues left behind by those who were trapped inside.