You can use this function to check that whether the floor is level or not when buying a new house.

Click Level Measure in the menu and you can find an emulational gradienter within a bubble on your phone screen. Put your phone on the surface of which you want to check and you can conclude the result by the bubble's shift.

One direction the bubble moved to indicated that side is higher than other sides. If the bubble moved to the center of the gradienter finally, that tells you the surface is extremely level.