Find out the platform of the game "Final Fantasy XIII-2".
platform of the game refers to platform_name; "Final Fantasy XIII-2" refers to game_name = 'Final Fantasy XIII-2';
SELECT T4.platform_name FROM game AS T1 INNER JOIN game_publisher AS T2 ON T1.id = T2.game_id INNER JOIN game_platform AS T3 ON T2.id = T3.game_publisher_id INNER JOIN platform AS T4 ON T3.platform_id = T4.id WHERE T1.game_name = 'Final Fantasy XIII-2'