Action puzzler Magrunner: Dark Pulse is free on Steam (opens in new tab) from right now until August 27 at 1 pm Pacific. Released in 2013, Magrunner is developer Frogwares' combination of cyberpunk sci-fi and Cthulhu mythos. It's a very much a post-Portal 2 action-adventure puzzle game: You use a magnetic glove to polarize objects and manipulate them.
Also, there are Cthulhu monsters to avoid, of course.
I remember it being decent fun years ago, and I'd recommend it at the price of free. It's a great weekend binge game, since it only takes about nine hours to beat, though as I recall the back half isn't quite as good as the front half. You can claim a free copy of Magrunner: Dark Pulse on Steam.
It's also Frogwares' 20th anniversary, which is why Magrunner is free, and a ton of their adventure and mystery games are on sale. Most of their Sherlock Holmes games are 75-90% off on the developer's Steam page, if that's your jam. The sale lasts until September 1st.
Frogwares has been in headlines recently due to a legal dispute with publisher Nacon, who funded 2019 game The Sinking City. For now, The Sinking City isn't available on Steam, although you can still get it on Frogwares' website (opens in new tab).