If you're a fan of iOS and Android shoot-'em-up Shadowgun, you'll be pleased to read that you now have the chance to influence the game's storyline. Oh, and win a T-shirt while you do it.

Madfinger Games is currently running a competition over on its Facebook page which invites you to invent a new "badass" for Shadowgun protagonist John Slade to face off against.

You'll need to think of a name and some powers and abilities, as well as a brief backstory. The three best entries will all win one of the T-shirts in the photo below.

To participate, simply head on over to the Shadowgun Facebook page and let your imagination run wild.

Shadowgun is available on iOS for £2.99 / $4.99 [buy], and on Android for £3.49 [buy].