Now we have a single-player mode where each chapter you can play with a soldier, and you need to use his skills in order to finish the chapter. For now, only the chapter 1 is available.
Campaign has different rules:
1. Character has infinite ammo, but you still need to recharge;
2. Zombies has a lot less life;
3. Zombies dealt a lot more damage;
4. There is no checkpoint;
5. Movement is reducced by a half;
6. Grenades insta kill zombies and give damage to players;
7. Grenades bounciness and friction works different;
8. Granades and shoots damage everyone including you and NPCs;
9. Grenades has less explosion range;
10. Barricades has 190 seconds life span;

Chapter 1:
I don't want to release any spoiler, but with the gunner you'll need to blow walls, barricade doors, and of course, kill zombies.