Back when Nintendo first made the announcement, there was a bit of confusion as it was suggested that it could be launched on Android first, but Nintendo later clarified by saying it would launch on both platforms simultaneously. The game is free-to-play but there are in-app purchases so do take that into consideration when playing the game.
According to Nintendo’s description, “Take part in strategic turn-based battles streamlined for on-the-go play with maps that fit in the palm of your hand! You’ll need to think hard about the advantages and disadvantages of each Hero’s weapon—and even evaluate the map itself as you battle. Lead your army with easy touch and drag controls, including the ability to attack by simply swiping an ally over an enemy.”