What just happened? The idea that Gears of Wars, the third-person, cover-based shooter, could work as a turn-based tactics game might have raised eyebrows when it was first suggested, but Gears Tactics has proved the naysayers wrong. The new title releases later today, and it’s already topping Steam’s ‘Top Selling’ chart.

Developed by Splash Damage in conjunction with The Coalition, Gears Tactics borrows heavily from the XCOM series. It’s set 12 years before the first Gears of War and puts players in the boots of Gabe Diaz—the father of Gears 5 protagonist Kait Diaz. You must recruit, develop, and command squads as they hunt Ukkon, leader of the Locust army, who is making monsters.

Gears Tactics unlocks on Steam in about six hours (at the time of writing), but the number of preorders has already pushed it to the top of the best-seller list. What’s slightly surprising about this is that it’s part of the Xbox Game Pass for PC, so those who subscribe to Microsoft’s service can play it for free. It seems plenty of people still prefer to buy their games outright on Steam.

Pre-release reviews have been mostly very positive, with the majority of sites awarding it between 8 and 9 out of ten.

Gears Tactics is also having to compete with a surprise new entry in the XCOM franchise. Released last week, XCOM: Chimera Squad is a standalone follow-up to XCOM 2. It’s also gained mostly positive reviews from critics and players, and it costs just $9.99. It's certainly a great time for fans of the genre.