Lazymanzoid18hHalf-LifeI just finished Half-Life 2, it was fantastic. I am now onto the episodes which for some reason are located at tools.
Episodes has been delisted from Steam, they are present in tools if you want to use mods from before the 20 year anniversary update. You don't need to use those in tools to play the episodes now, they are included in the base Half-Life 2.