Question about online challenge system

[zGeneral]

Hi

I had Gratuitous Space Battles and it is one of my favorite games.
sharing fleets as a challenge was very addictive.

how does this game compare to it?

From what I have understood, this is a tower defense RTS. i.e. it is not like GSB where u just sit back and watch the simulation.

if I submit a defense challenge, how do my defenses play? I mean, do I have to script the AI reactions. or is it just static defenses.

I watched few youtube about the game but the online challenge system is still not clear to me, anyone?