HL2's 20th Anniversary - Everything I Learned about Half Life 2 YouTube · 2kliksphilip Half-Life 2's 20th Anniversary Update Is Pretty Cool YouTube · Radiation Hazard Free Community Mods
You no longer need separate downloads for the episodic sequels; they are now accessible from the main menu .
If you are downloading the game today, you are likely getting the definitive version. Key "deep" improvements include:
Updates to lighting, shadow map resolution, and "radial fog" for better horizon blending .
Once you own the base game, a vast library of "free to play" mods becomes available: Half-Life 2 RTX on Steam