Graveyard Keeper 2 was announced this month at the Triple-I Initiative, and to celebrate that the original was made available free for a limited time. It's a sensible way to get people familiar with the series and to build anticipation for the sequel, but there's another upside to this kind of giveaway. As Alex Nichiporchik, CEO of publisher Tinybuild explained on Twitter, it's earned "almost 250k usd from selling DLCs for the original."
And that's just on Steam, where the DLC is currently 80% off. (The giveaway for the base game has ended, I'm afraid.) The main purpose of the giveaway is to draw attention to the upcoming sequel of course, and that seems to have worked as well. In a followup tweet, Nichiporchik announced Graveyard Keeper 2 was in Steam's top 100 most-wishlisted games, having been wishlisted 450,000 times.
