Action puzzler Magrunner: Dark Pulse is free on Steam 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.