Lego-themed action-adventure The Lego Ninjago Movie Video Game is free for a limited time on Steam. The game normally costs 29.99 euro but for the next seven days you can get it for free. The offer ends on Friday, May 22.
To get the game, just go to The Lego Ninjago Movie Video Game page on Steam, and click the "Add to Account" button. Once you get the game, it will be yours forever.