You can clone with
HTTPS or Subversion.
We can have:
-> Simple attack zombie (Does damage to humans/town)
-> Converter Zombie ( Converts Humans but does no damage to barriers or towns)
-> Destroyer/Heavy Zombie (Can destroy barriers or breakable walls)
so there should be some widgets like:
Simple attack zombie , that get decreased when choosing it and applying it to a zombie?
so this info how many zombies of a kind one can get needs to go to levelfile too
ya, a min_zombies_left_to_succeed is needed