にゃんこ大戦争 (Nyanko daisensō, Nyanko Great War) is a Tower Defense and Casual game published by PONOS. It's a basic free-to-play game. Since the start of the iOS version in November 25th, 2012, the game reached 22.22 million downloads in February 2016. The game also has 2 alternate versions in Korean (냥코 대전쟁 nyan-ko dae-jeon-jaeng, Cat Catastrophe) and English languages. There is a Nintendo 3DS version of the game: とびだす！にゃんこ大戦争 (Tobidasu! Nyanko daisensō) was released in May 2015.
The gameplay is quite simple. Just tap the unit on the bottom of the screen and it will send out that unit to face the enemy units.