Of course, there is a difference between a demo focusing on implementing new features then the software that we are shipping. But yes, it was extremely impressive and it's no surprise that he is leading much of our engineering team (beyond software, as well) today.
On a side note, what are higher ups looking for in a young applicant? I'm graduating in the fall with a CS Undergrad and don't have any startup contacts (I live in a smaller town in Missouri) and am trying to get my foot in the door somewhere that is doing interesting work.
Projects. Contribute to open source as much as possible and build as much stuff as possible that you can show off. Then you should have no issue finding something interesting. Might have a better chance searching outside your hometown though.
Passion. Engagement. Curiosity. Being the absolute best possible at something - I don't really care what, but being mediocre at lots of things is a turnoff. Ability to learn new stuff, more so than any specific skill (although YMMV with this one).
Any interview I walk out of thinking I've had a 2-way meeting of minds, a genuinely engaged conversation as if we're already peers, rather than an attempt to simply answer a list of questions is going to do well.
I am curious if the demo app was built using some pre-existing libraries/frameworks or even UI widgets. Because, based on the info available on the demo site, even if the author knew exactly what he was going to develop and the tech behind it, the sheer amount of coding required to build such an app from scratch would take way more than 3 days.
Of course, there is a difference between a demo focusing on implementing new features then the software that we are shipping. But yes, it was extremely impressive and it's no surprise that he is leading much of our engineering team (beyond software, as well) today.