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Half-Life 2 is currently 100% off for its 20th anniversary, plus a major update
(store.steampowered.com)
Bonus: it also seems that the episodes have been rolled into the base game. Full details of the anniversary update.
Not unless they had some special bundle for HL2 I can't remember.
Ep1 had to be purchased. Ep2 came with The Orange Box (which also contained TF2 and Portal 1 as well as Richochet, though it wasn't advertised).
Pretty sure when Orange Box was released, it included HL2 and HL2 Episode 1 in addition to HL2 Episode 2. Hard to remember because there were so many good games that came from that one purchase.
I probably just remember EP2 only because it was released then and how I got it. I already had HL2 and ep1 at the time.