curved active bed level

I prefer an active level before large prints and i could not find anything that took up the whole perimeter of the bed but also had continual curved surfaces.

Active bed level, Set X/Y size to be ~20-30mm smaller than bed size.
set z height to layer thickness.
default is 180x180x0.2
Monitor and adjust level as it prints.
Can help with small errors that don't pop up with square shapes.

Uses a very small amount of filament and only takes a few minutes.