Infinite Crisis developer Turbine is developing Batman: Arkham Underworld, a new spin-off for iPhone and iPad.

The app will let you build a hideout, recruit henchmen and command super-villains such as Riddler, Killer Croc and Harley Quinn.

The aim of the game is to take on Batman himself - when you're powered up enough. You can sign up for the game's beta now via Arkham Underworld.com.

Meanwhile the game's bigger brother, Rocksteady's Batman: Arkham Knight, is due to land on PC, PlayStation 4 and Xbox One worldwide on 2nd June.

Turbine is also working on a new, as-yet-untitled Game of Thrones game. Described as a combat strategy affair based around the franchise's TV series, the game's aim is to let you raise an army of soldiers and spies to dominate Westeros.

Both titles will be published by Warner Bros. - but there's no word yet on when.