A long time ago, I thought I'd worked out the system that determines when zombies spawn and how often they spawn in the original PvZ.

Basically, what I thought was this:

Each zombie has its own threat rating, and every wave (huge or otherwise) would have a difficulty rating. The combined threat rating of all zombies in the wave must add up to the difficulty rating, no more, no less.

I determined that the difficulty ratings for the waves in a normal level were this: 1, 1, 1, 2, 2, 3, 3, 3, 4, 10 (1st Flag), 5, 5, 5, 6, 6, 7, 7, 7, 8, 20 (2nd Flag), and so on.

There ARE exceptions, like conveyor-belt levels and mini-games, and in some normal levels, a zombie will be guaranteed to spawn in a wave where it can't normally (example: in 5-8, a Garg spawns at wave 11).

I also worked out some of the zombie's threat ratings:

  • Zombie/Flag: 1.
  • Cone/Newspaper: 2.
  • Vaulter/Snorkel/Dolphin/Balloon: 3.
  • Bucket/Door: 4.
  • Garg: 10.

Also, I realized certain zombies were prevented from spawning in early waves. For example: Ducky Tubers spawn at about wave 5 at the earliest, while Snorkellers and Dolphin Riders can't spawn until wave 10.

Now, here's the big discovery, and the reason I finally decided to tell people this. I found PROOF.

The developer documentation section at the bottom of the page not only confirm my theory, but also include info I didn't think about, like zombie "weights", AND they prove that PvZ2 uses the same system (although I think the wave's difficulty ratings are VERY different).

The whole point of this blog is that this info is very important, and should be added somewhere on the mainspace. Also, using this knowledge of PvZ1's wave "difficulty ratings", we can all try to work out the threat ratings of the other zombies too.