I was originally rejected before even getting to an interview, but after a bit of back and forth with the recruiter, I was able to get a first-round interview (Valve is generally looking for 5+ YoE, and I had 3).

The interview was great. I had two interviewers who were both very personable and seemed to know their stuff very well. We discussed each of our work histories and some info about projects, like most interviews. There was one primary technical question: implementing atoi.

After going through the implementation, we had some time to discuss. During which, I asked a number of questions about Valve's unique structure and the work culture there.

After the interview, I received a response that I did well on the technical interview, but they are generally looking for more experienced developers due to Valve's flat structure. It was recommended that I apply again when I get more experience.

Implementing atoi in the language of choice (C++ preferred).