A mysterious new Forza series spin-off is in development for Xbox 360, Microsoft revealed at its Spring Showcase. What Forza Horizon will actually bring is a mystery, though, as Microsoft had nothing to say about it and simply showed a tone-setting trailer made from stock footage. Come, let's watch it together and guess what the game's about.

Canny viewers will notice that an awful lot of the video focuses not on cars driving fast, but rather festivities with DJs, fairground rides, crowds of people waving their hands, and ladies in bikinis.

Forza 4's 'car culture' aspects were purely mechanical, with a car showroom for those who get a bit sweaty looking at chrome and carbon fiber to leer at automobiles. Judging by the teaser trailer, Horizon may be hoping to grab a wider range of people wot like it when the brum-brum goes zoom-zoom, which could likely involve taking a less sim-y, more arcade-y approach.

Development is being handheld by Playground Games, a fledgling English studio formed by Codemasters veterans. In 2010, Dirt developer Codies accused Playground of poaching its staff to jump-start its own racing team. Evidently, it was staffing up to make Horizon.

Forza Horizon is getting a retail release on Xbox 360 this fall.