[Classic rules]
Life = 3
DestroyBombsAfterExplosion = false
LockedByBombs = true

[Ground]
Damage = true
Destroy = false

[Bridge]
Damage = true
Destroy = true

Update 02.12.2002
-----------------
Right now, each theme already contains OOP-style options, just like:

[desert]
Name=Desert
Name[de]=Wüste
bomb.frames=10

This could be extended:
ground.damage=true
ground.destroy=true
rules.lockedbybombs=true
rules.destroybombs=true
rules.life=2