Universe[]
My theory is that all valve games are in the same universe and i have proof in portal glados says the word "Black Mesa" Now black mesa is in the orginal Half-Life so they must be in the same universe and in portal she says something "reanimating the dead maybe" guess what game that has undead charcters "Left 4 dead" it was all caused beacuse of glados and now zombies roam the city attacking and killing humans and in Half life 2 it happens after Half-Life and i think Portal 2 happens after Half-Life 2 In the ending of Portal 2 we see chell go outside guess what game you are actually outside Garry,s Mod so i have a lot of questions but i think this is a pretty good theory.