Zen Studios' hybrid tower defense game and physics puzzler CastleStorm is making its iOS and Android debut later this spring as a free-to-play game.

Rechristened CastleStorm: Free to Siege, the upcoming mobile port features four playable nations, each of which boasts its own campaign across a total of 150 included levels. Free to Siege includes new spell types not seen in the game's previous console and Steam releases, and offers a redesigned control scheme suited for touch screens.

Players looking to join the siege early can sign up for a private beta on Android platforms.

[Image: Zen Studios]