This games full title is "Chess Challenges for Clever Minds!" and it's the latest game from RavelMatic. The concept is beautifully simple: Destroy the bad kings castle by blowing away all the bricks holding it up.
To do this you complete chess challenges. The more skulls on the brick (level) you select, the harder it is. They start off nice and easy, just sliding one piece into place for example, but quickly escalate into real challenges.