Older promo-videos, light on detail but similarly-relevant:

Networking: https://www.youtube.com/watch?v=GqhhFl5zgA0

Level design: https://www.youtube.com/watch?v=ExZtISgOxEQ

Smoke physics: https://www.youtube.com/watch?v=_y9MpNcAitQ

Rankings: https://www.youtube.com/watch?v=s6BNHro0vSg