manic pollen
I think I like the idea that building auras (shield, clean pollution) should be limited/fueled, so I added the feature that cleaning pollution requires a specific building with fuel in it. This fuel is depleted each time a clean event occurs.
Having limited auras maintains tension in the game and gives the player a reason to continue to "dig" the map.
One issue appears to be that there is a deadlock where if you have no fuel for the cleaner, you can't "dig" to get more fuel.
There is a main spawner building that spawns fuel and can help prevent this - maybe the idea is just that this also needs to be kept clean. That building being covered by pollution is already a lose condition, so maybe that's just how it has to be...