You can play Valve’s classic Half-Life series on PC for free through March, as Valve rolls out promotion in preparation for Half-Life: Alyx.

Valves classic narrative shooter series Half-Life is now free on Steam, and will stay free for the next two months.
With the launch of virtual reality shooter Half-Life: Alyx set for March, Valve is opening up the 2004 digital remaster of 1998s Half-Life for free, as well as DLC missions Opposing Force and Blue Shift. Half-Life 2 is also part of the package, as well as follow-ups Half-Life 2: Episode One and Episode Two. The value of the separate items on offer is around $56.
A Valve statement on the deal said that the promotion is designed to pave the way for Half-Life: Alyx which is set before the events of Half-Life 2 and its subsequent episodes. The games share characters and story elements, Valve said. The Half-Life: Alyx team believes that the best way to enjoy the new game is to play through the old ones, especially Half-Life 2 and the episodes, so we want to make that as easy as possible.
The Half-Life games center on scientist Gordon Freeman who must escape locations where mutants and aliens roam, making use of weapons and solving puzzles. The first games expansions feature other protagonists Black Mesa security guard Barney Calhoun and military specialist Adrian Shephard and were developed by Gearbox Software. In Half-Life: Alyx VR players will take on the role of Freemans ally Alyx Vance, as she once again does battle with enemies, making use of a gravity gun. The Half-Life games are available for Windows PC, Mac, and Linux.