I really enjoy the wide variety of the 24xx you've designed. I'm wondering if you have a little guidance on what an opening Is as you've imagined it for the game Codebreakers. Does this follow Hollywood inspiration for telephones and mirrors, ingesting substances or finding tricky glitches in the outside world or what? 

Thank you for your kind words, and yes—my inspirations are not subtle!

The character creation process in Codebreakers implies everybody in the group starts the game already aware of the truth of the simulation, already members of a cell. The presumed default scenario setup is a contact giving the group the details of an operation, with a nod to either of a couple other contacts the group might hit up next. It makes for easy one-shots and episodic series/campaigns. 

My personal preference is to go much more bonkers, though: Don't start anybody with the "Simulation" skill—and perhaps even make characters in some other 24XX game entirely. Make their entry into Codebreakers feel weird and jarring as they realize they're in a simulation. One adventure I wrote (yet to be transcribed online from a notebook!) transitions from a wizard's tower, trying to open a portal to another world, to an office building with a computer monitor where messages from Mothman urge you to get out right now.