How to work on a project from 2 different computers at the same time ?

I will soon attend a game making contest with my friend (It’s a 2 person team contest) and we’ll use Unity. The contest will start in the morning and last 12 hours, that being the time-limit for us to create the game. We’ll be told what the game is about on the spot.

So basically, 2 persons need to create a game in 12 hours. We’ll use 2 laptops, so I ask how can we link them in order to work on the same project from our 2 different machines at the same time ?

This
It does what you want, for free. Some restrictions do apply but it’s completely GIT integrated and such.

Just use Git or Mercurial or SVN or some other versioning system you are comfy with. In the versioning ignore (don’t share) everything except for Assets folder and Project Settings, the rest is generated locally from those data (also it’s huge).