refactor umbraAboveBelowOrOnScreen into umbraBehavior object
refactor umbraAboveBelowOrOnScreen into umbraBehavior object

nlevitt/brozzler,internetarchive/brozzler,internetarchive/brozzler,nlevitt/brozzler,internetarchive/brozzler,vonrosen/umbra,nlevitt/brozzler,internetarchive/brozzler,vonrosen/umbra,internetarchive/umbra,nlevitt/brozzler,nlevitt/brozzler