It's a Fog of War effect using MMF2 HWA, and Muddy Mole idea of Substractive layers. In other words you've got engine for FOW with 20k fog areas.
Issue I got is that MMF is not always Adding Backdrop Which is quite irritating.
Everything is commented!
It uses 3 Active Objects, 1 List Object, 1 String Parser and 4 Layers, and 2 backdrop Objects.
Any comments and modifications are welcome in this thread!