Information is definitely out-dated, and you shouldn't really take it to heart.
The Zombie Levelling System was a small system for normal zombies. This was replaced by the Deadvelopment Center.
They do not save each round, but they do carry over in each wave of Arena. Each time you get killed as any mob or use Claw to damage a survivor, you earn experience to level up further. You still get points if you claw a survivor with a forcefield or a dead survivor. Levelling up earns you 3 Skill Points.
Skill Points were used to improve your statistics. Underneath the health and stamina bar contains your XP bar. Once it reaches 100%, three buttons will pop-up. You can select to upgrade your health, damage or speed.
125 Base HP (+10 HP for every skill point)
10 Base Damage (+1 Damage for every skill point)
19 Base Walkspeed (+1 Walkspeed for every skill point)
|Level Zero||0 Experience|
|Level One||5 Experience (5 total)|
|Level Two||8 Experience (13 total)|
|Level Three||12 Experience (25 total)|
|Level Four||17 Experience (38 total)|
|Level Five||23 Experience (61 total)|
|Level Six||30 Experience (91 total)|
|Level Seven||38 Experience (129 total)|
|Level Eight||47 Experience (176 total)|
|Level Nine||57 Experience (233 total)|
|Level Ten||68 Experience (301 total)|
|Level Eleven||The apparent maximum level, reaching it will causing you to earn zero experience points. Thus, never being able to level up.|
- When you reach Level Five, Upgrade Climb is free, but its really only useful if the map supports it to begin with.
- You only get points for clawing survivors as a Normal Zombie, Ticker, Edgar, Swarmer and Digger.
- Any other attack will not net you any points.
- Each time you level up, you get EXP.
- For example, levelling up once gets you 15 EXP, the next level gets you 25 EXP, the next gets you 35 EXP and so on.
- Skill Points used to carry over to the next round, to use as a zombie, while this feature was being tested in Debug. As this aspect of the system was easily abusable, this was removed.
- In v1.2.0, the GUI for this feature was overhauled.
- Upgrading damage affected the damage of Diggers too.