Incredibly cool concept. Put in a seed (or roll randomly) and fall into an old sourcemod community map. You can come across other people on the same seed as yourself. High chance to spawn into the void, you have to keep rerolling.
Make sure HL2 and CS:S are installed. TF2 as well if you can help it
Just tried this, and for whatever reason I get a black screen with crosshairs and nothing else...
I figured it out. I had to run the game as Admin for some reason so it could download the assets. It's a real vibe for sure!