Not sure how long it goes for. They have flash deals like steam used to as well
https://www.greenmangaming.com/
Purchased Surviving Mars, at 44% off. The random tech tree and maps intrigued me, also a growing mod support on the Steam workshop, so bought it.
If anyone watches 'Worth a Buy' reviews he has a link to GMG on his videos that will give money to charity. I'm not affiliated with that channel at all, just thought it was a nice touch. And find his reviews a good laugh.