Board Thread:Plants vs. Zombies 2: It's About Time/@comment-24725728-20140512192458/@comment-5505065-20140602103829

1. http://www.tfaw.com/Profile/The-Art-Of-Plants-Vs.-Zombies:-A-Visual-Retro-Retropsee-Book-HC___444251 (Click "Preview this title now!")

http://www.insidemobileapps.com/2013/08/14/insider-qa-plants-vs-zombies-2/ (Scroll down)

http://www.gameinformer.com/b/features/archive/2013/08/14/looking-back-on-the-development-of-plants-vs-zombies-2.aspx (Scroll down)

And many more.

2. I agree.

3. The Stone Age!

4. Maybe it was a concept art for the Stone Age?