1. Scroll all the way up
2. Look at the sides of your monitor screen and notice the grass + trees and stuff
3. Scroll down slowly until you are at the bottom, still looking at the sides
4. Look at the bottom, it's the core
I JUST noticed this and I have been actively on the forums since about june / july of last year, and I think it is very clever.
Woah... Jeez I'm blind.
If only it were open. But then that'd be a spoiler.
:(