1. Didive map into zones.
2. Set (and show) zombie limit in a zone. "980/1000zombies in zone X"
3. Grow rate of zombies for set zone (100%, meaning in 1 day zombie amount wil grow back to 100% of that zones limit (1000zeds for zone X).
4. Supress grow rate by
- Targeting zone with mortar team*(base facility for first base, which you'll have to scavange parts for/attack a militairy base). (Munitions upkeep)
- Sent "Troops" (characters) on patrol. The more troops/the better the skills of those troops, the more growth supression. (Less munitions upkeep than mortar, but more food).
5. If said zone has 0 grow rate, and bring total amount to 0. You can claim a small forward base (needs to be manned, or growth will be >0)
6. Same with adjacend zones, (but they are increasingly harder. Higher limit/higher grow rate). (So before you can get a next zone, you need to recruit/train more, loot more, have a stronger base etc).
7. After some zones, be able to attack a zone with a military base, after securing being able to make Artillery support from there(mortar became to weak), and more soldier room etc.
8. After some zone's Artillery becomes to weak. So you have to attack a zone with an airbase for airstrikes...
You'll slowly change the zombie map to a map controlled by patrolling soldiers. Every zone increases difficulty, and provides something of strategic value. A suburb zone gives more recruits, a factory zone more ammo(more mortar teams). A militairy zone gives artillerybase or later airfield (small base just weapons) farm zone food etc. So you need to scavange parts for those good base upgrades you need to get to further zones. This way you're always expanding/growing"PROGRESSING".