Hey! my name is Sahar and I've worked on this project along with PouYad.
I think that the most important thing that we did that helped us in regards to team size was consistently doing voice chats and not relying on occasional texts, it was hard even doing that because we come each from a different place and time zone; but it was in my opinion crucial to maintain between us a common understanding of ever-changing ideas and to keep track of tasks and timing. I doubt that we would have been able to do so much with so "little" trouble in 10 days if each of us hadn't made compromises to be present and active!
another benefit of active discussion is that we were our own checks and balances system. we all came up with some good and some not so good ideas, and it was important that as a group we redirected each other when needed, to keep expectations from each other and the project realistic.
that is my experience at least, and GitHub also helped.