The promotion is timed to coincide with the 25th anniversary of the series.
Valve has launched a free distribution of the first Half-Life on Steam. To get the game, just go to it store page and add to your account. The promotion will last until November 20.
The game has also been updated to include Steam Deck compatibility, gamepad support, and other features.
In addition, Valve released a documentary dedicated to Half-Life. And other games in the Half-Life series received discounts on Steam.