From Wikipedia:
Crystal Defenders: Vanguard Storm (クリスタル・ディフェンダーズ ヴァンガード・ストーム Kurisutaru Difendāzu Vangādo Sutōm) is a turn-based strategy/defensive simulation game that requires players to defend their position on the right from monsters that are invading from the left side. It was released for the iOS platform as part of the App Store in May 2009. As with the original Crystal Defenders, it features jobs from Final Fantasy Tactics A2: Grimoire of the Rift.
Vanguard Storm is the first Square Enix game to be designed especially for the iPhone touch-screen. The objective of the game is to prevent enemy monsters from successfully moving from the left side of the screen to the right through the strategic placement of the player's combat units. The game is turn-based; each turn the enemy monsters advance one or more spaces and attack the player's units if they are in range. Players must adjust the positioning of their units to either block the monsters from advancing and/or attack. There are different unit types that are provided for the player at the beginning and at various points of each map, each having different attacking capabilities and stats.