We're actually going to release something that we're not talking about yet that will give a little bit of the story of the interim time," Erik Wolpaw, one of the writers on Portal 2 told me at PAX East today. "We're doing that before release.

'Portal is after Half-Life 1 and before Half-Life 2,' Wolpaw said. 'Without getting into it too much, Portal 2 is further down the line.' I asked if that meant that Portal 2 is, say, after Half-Life Episode 2. He didn't want to get into that.

The Portal and Half-Life games co-exist, but they won't crossover too much, Wolpaw said. 'We tried to keep as light a touch about it as we did in Portal 1. Fans of Half-Life will notice some things, but if you haven't played Half-Life they'll just kind of pass right by you. You're not going to see Gordon tromping through the facility.' He likened it to how the X-Files had an overarching plot but then also standalone episodes that were a little looser. 'Aperture Science is kind of this fun-house of science, this bubble in the otherwise serious Half-Life universe.'