Minenfelder verfallen jeden Zug und werden dadurch kleiner.

Mine_units_after_decay =
   Trunc(Mine_units * (100 - MineDecayRate) / 100)
                     ...bei normalen Minenfeldern
   Trunc(Mine_units * (100 - WebMineDecayRate) / 100)
                     ...bei Fangminenfeldern
This is a testing version.
It may be incomplete, and have more bugs (or features) than the public live version at planetscentral.com.