Hundreds of games get released on Steam every month, and tens of thousands are released every year. Some of those are major blockbuster productions; most are the work of small studios. It's hard to stand out from the crowd, especially if you're an Australian studio with a small staff, and even smaller marketing budget.
But amongst the tens of thousands of games filling up Valve's content servers, there is one that sits at the very top. And that game happens to be Australian.