We started with a single developer and an artist. And two weeks ago a GUI developer joined the team. The team has been working full time on this.

How we did it? Well, we came up with a few leap of faith questions, like : "Nowadays most football games are too complicated to play and if we build what feels like arcade, people would enjoy playing it" and we started building minimum thing which we can test if we were right or not. This is where we are by the end of the 5th week :)