Cats and dogs interaction (on the streets). Agents(cats, dogs) have a few traits like age, energy and age of death. Cats can kill dogs if dogs' age more then 40 and take their energy. There are birds that can be eaten by cats and then by dogs if all cats are already dead.
Also there is a house, what cats can enter(basically they are deleted after collision with the house) and dogs can't.
Cats and dogs get weeker and older, birds just exist...
The model stops working when there are no dogs or no birds.