GMail and Google Now were also prototyped in one day, as was Linux. The hard part is the years of refinement that come after that.<p>I guess the lesson to take is that <i>big working systems are built on small working systems</i>. You don't get a big system by envisioning the final result, finding someone to fund you, and getting lots of people to build it for you. You take the smallest possible first step, see if it works, and then learn from it and expand it.