Interns have worked on various components of our open source game engine project and its supporting libraries. They've developed data structures that beat C++'s standard library on performance, and created the C++ string class that fully supports both UTF-8 while remaining compatible with std::string. They've laid the groundwork for a programming language, an educational content engine, and a vector animation engine.
The most amazing part of this for me is watching first- and second-year CS majors come in with minimal knowledge of, say, Java, and become skilled C++ developers as time goes on.
We typically bring on interns from the local area because, although we're remote, I believe in the value of the team being able to meet in person from time-to-time. However, we do have a few completely remote workers. We're also an open source company, so even if someone doesn't join as a formal intern, they can still get some experience by being a regular contributor.
Also, we don't require students to come from the universities. We have good working relationships with the faculty at two of the biggest, which means we can offer college credit to their students for the internship, so most of our interns come from there. However, we've been known to bring on folks from elsewhere.
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