These are the demo reels posted on YouTube by Gray Horsfield, a former Valve employee. Among Valve titles that we know and love, like Half-Life 2: Episode 2 and Left 4 Dead 2, some interesting things are shown. Like the "Swarm Dynamics" test and the (SOB related?) space stuff in the main reel. Original sources: https://www.youtube.com/watch?v=zW6FtY6XrJM https://www.youtube.com/watch?v=9mS4-2cIHpg