Can you give an explanation about what each type of unit does?
Fighters target bombers and fighters. Satellites target ICBMs. Bombers and ICBMs target factories, cities, bases, and defcon. Bombers target in that order; ICBMs seem to target randomly.
Game over when defcon is destroyed.
Launching an ICBM requires defcon Defcon changes to 4, 3, 2, and 1 if a bombers crosses the circular boundaries (radar?) around the center. You can see this happen when the boundary flashes.