This article describes design decisions that will be rediscussed before their implementation in the future, and as such are not final.
Sandbox Mode will be unlocked once your species has reached Ascension. You will basically be able to do whatever you want, from controlling a fish to creating a planet. It is your area for unrestricted creation.
You will have your own little section blank space where you can create many things and troll animals to hearts content. (Come on, who's not gonna use this to annoy organisms. I am.)