In floor 81 in 100 floors you will see a number of math symbols and the numbers 6s. You will also see an equal sign on the left side of the door. To be exact, you have 2 X signs and 3 + signs and 4x 6 infinity numbers. These are all on the square in the middle of the door in which you need to find the answer to.
There is no current solution, comment below if you know. We will update live as solutions are found.
Solution was graciously contributed by Mattie
You must turn your device upside down then press 6 x 6 then the door will open. This is a motion sensor stage.