Take a look at some of the earliest designs for Plants vs. Zombies

The original Plants vs. Zombies, a charming tower defense game that spawned a prolific and still-running series, has turned 10 years old. To commemorate the release, the game’s creator George Fan has shared some of his early design doodles.

His notes offer a quick but interesting look at what ended up becoming an iconic game of its generation. Fan shared those design sketches in a thread on Twitter, running through how different character types and small mechanics appeared and evolved in the early days of planning for the game.

For instance, he says at one point a prototype of Plants vs. Zombies was a Magic: The Gathering-inspired deck building game. Another early idea of the game had plants fighting off aliens, specifically those from another PopCap-published game called Insaniquarium, but that idea was scrapped once Fan says he sketched the perfect zombie.

A peek at the rest of his notes can be found in the full twitter thread and, for another look at Fan’s process for creating Plants vs. Zombies (specifically the delicate business of teaching game mechanics to players), take a look at his talk from GDC 2012.