https://www.gamespot.com/articles/free-steam-game-to-keep-forever-but-hurry/1100-6462001/

When it comes to getting free games, no platform is better served than PC. While all platforms these days are home to free-to-play games like Fortnite, it's mainly PC gamers who regularly get to scoop up free copies of games that normally cost money. Such is the case right now with The Tiny Bang Story. This PC and Mac game from 2011 is currently free for anyone to download and keep forever--provided you add it to your library before 10 AM PT (1 PM ET) on Tuesday, September 25.

The Tiny Bang Story is a puzzle/adventure game about a small planet that gets hit by a meteor. The impact destroys many of the machines that keep the planet going and disrupts life for the inhabitants. Naturally, it's your job to help put things back together.