Unstoppable Gorg has got out of control. Not only is it destroying all aliens and humans, it's turned on its own price tag.

That means this Gold Award-winning tower defence game and satire of B-movie sci-fi is currently free on iOS.

Yep, if you download it now you'll save yourself £2.99 / $4.99. Not bad.

If you're wondering what it's all about, it's simple: aliens are invading so you've got to bolster defensive positions across the solar system.

Our reviewer called it a "clever and challenging spin on the tower defence genre, overlaid with an elaborate science fiction schtick which doesn't outstay its welcome".

Presumably, the game isn't going to be free forever, so be quick and pick Unstoppable Gorg up and save those precious pennies (and humans, I guess).