GS: Will vehicles return in this episode? Half-Life 2 featured the dune buggy and the air boat, but Episode One took place entirely on foot. Will either of those vehicles return, or is there something new to look forward to?

EJ: There will be a new vehicle in Episode Two. The buggy from Half-Life 2 was built by a group of rebels that was clearly skilled at welding together a tube frame but was a bit lacking in the horsepower department. In this episode you'll be driving a car built by someone with a lot of knowledge of older American hot rods.

GS: Computing power has increased substantially since Half-Life 2. PCs now have dual-core CPUs, and the Xbox 360 and PS3 are powerful multicore systems. Will Episode Two support multicore CPUs for better physics or AI?

EJ: We've built a system for dealing with multiple cores and threading called hybrid threading. As opposed to using coarse- or fine-grained threading, we take the approach of building a system into the engine that makes the right decisions about how to deal with multiple cores on the CPU.

In Episode Two this will translate in a number of ways, benefiting not only systems that were traditionally CPU based, such as artificial intelligence and physics, but also systems that are on the graphics side. We went with this approach because it scales well over time. Desktop processors are going to have more cores over time for us to take advantage of, so we took the route that requires more work up-front so we can keep pace with our customers' hardware as we move from dual core to quad core and beyond.