On which platform was Panzer Tactics released in 2007?
platform refers to platform_name; Panzer Tactics refers to game_name = 'Panzer Tactics'; released in 2007 refers to release_year = 2007
SELECT T5.platform_name FROM game_publisher AS T1 INNER JOIN publisher AS T2 ON T1.publisher_id = T2.id INNER JOIN game AS T3 ON T1.game_id = T3.id INNER JOIN game_platform AS T4 ON T1.id = T4.game_publisher_id INNER JOIN platform AS T5 ON T4.platform_id = T5.id WHERE T3.game_name = 'Panzer Tactics' AND T4.release_year = 2007