Poland is one of the most prominent countries for game development in Europe. Studios like CD Projekt Red, Techland, 11 bit Studios, Bloober Team, Flying Wild Hog, The Astronauts, CI Games, and many others are very highly regarded. To celebrate the 100th anniversary of Poland regaining its independence, digital retailer GOG decided to discount many awesome titles. As you may be aware GOG provides DRM-free PC titles via its storefront and serves as one of Steam's main competitors.
A full list of games in the promotion can be found here. The offer is valid until November 12, so you still have a lot of time to think about your purchases. There's plenty to choose from... including some more recent releases like Frostpunk, Phantom Doctrine, and My Memory of Us.