While Fallout 76 grabbed most of the headlines, it wasn't the only game in Bethesda's post-apocalyptic series to get some attention at E3 2018. The studio also surprisingly released their popular mobile hit Fallout Shelter on both PlayStation 4 and Nintendo Switch. The best part? It's absolutely free.

Originally released for iOS and Android in 2015, Fallout Shelter is a management simulation that has players managing their own Vault. Players have to balance the happiness of inhabitants with needs such as food and power. In 2016, it saw a PC release, and then an Xbox One port was released in February of last year thanks to Microsoft's Xbox Play Anywhere program. It's been a huge success for the studio having been played by over 120 million people (which is more than every other Bethesda game combined).

Related: Fallout 76 Trailer: A Prequel 4 Times Bigger Than Any Other Fallout

Since it originally released in 2015, Fallout Shelter has received a number of free updates that added new features. Additions include a photo mode, cloud saving, a survival mode, a crafting system, and seasonal events. The PS4 and Switch versions will feature the current version of the game, and will have all of the enemies and features that were added post-launch.

While Fallout Shelter is free-to-play, it's worth noting that there are plenty of potential microtransactions and DLC itmes to buy. Some of the most expensive purchases include a truck of Nuka-Cola Quantum for $99.99, a bundle of 40 lunchboxes for $19.99, and 40 pet carriers for another $19.99. There's also a bunch of smaller items starting at $0.99, and this pricing scheme is how Bethesda makes money off the game despite the nonexistent entry cost.

While some of the monetization schemes are undeniably gross in Fallout Shelter, it's still a quality management sim. If one can overlook the issues with microtransactions (and they are optional), then they'll find a highly satisfying game. Plus, the admission price really can't be beat.

The fact that Fallout Shelter of all games (rather than their critical successes in The Elder Scrolls and Fallout role-playing games) is Bethesda's most played game by a huge margin is also quite telling. Free-to-play titles (especially on mobile) have a far higher potential player base than any other type of game. 120 million players is an incredible number for the studio, and it doesn't take much thought to figure out how huge the potential revenue is from the free-to-play title. It's one of the key reasons why Bethesda is going back to mobile with the upcoming The Elder Scrolls: Blades.

More: Every Video Game Trailer From E3 2018

Source: Bethesda