It's been a while, but a different game is being given away for free on the Epic Game Store.
The name of the game is Axiom Verge, a metroid-like game launched in 2015.
I don't know much about the game, but looks really good (if you like those type of games at least) and, well, it's free right now.
All you have to do is download the Epic Game Store from their website, log in or create an account if you don't have one, go to the "Store" menu located on the left, and click on the Axiom Verge image at the top of the screen.
And that's it. If you've been getting all the games they gave away for free, you should have 5 games in your library.
Hope you enjoy the game!