Happy's Humble Burger Farm is free to claim & keep forever until June 15, https://store.steampowered.com/app/1433340/Happys_Humble_Burger_Farm/ all you need to do is go to the store page, scroll down & click the "Add to Account" button, no immediate install is required, this is a promotional decision due to their new game Happy's Humble Burgatory to release on June 16 https://store.steampowered.com/app/3453910/Happys_Humble_BURGATORY/
which has been expanded to a co-op experience of 1-4 players