Don't overrate the skill of writing assembly, sure. But don't underestimate the software craftsmanship. Looking at the code, it's obviously expertly written. I'm not sure if I've ever had the pleasure of working with such a well thought out and documented code base.

And don't underestimate the skill of putting together the entire product: being able to create behavior that is relatably live-like for millions of people on such a limited Plattform may not be Apollo-Level genius but is exceptional nontheless.