Play Europa Universalis IV for Free

Europa Universalis IV is currently playable for free on Steam, offering the chance to try your hand at ruling a nation in Paradox Interactive's grand strategy sequel for Windows, macOS, and Linux. If you enjoy the game, it is also on sale for 75% off. This is presumably part of the 20th anniversary of Europa Universalis that included a giveaway of Europa Universalis II earlier this week (thanks SteamDB via Ant). Here's a quick outline:
Paradox Development Studio is back with the fourth installment of the award-winning Europa Universalis series. The empire building game Europa Universalis IV gives you control of a nation to guide through the years in order to create a dominant global empire. Rule your nation through the centuries, with unparalleled freedom, depth and historical accuracy. True exploration, trade, warfare and diplomacy will be brought to life in this epic title rife with rich strategic and tactical depth.