In which platform does the game titled 15 Days available?
platform refers to platform_name; the game titled 15 Days refers to game_name = '15 Days'
SELECT T1.platform_name FROM platform AS T1 INNER JOIN game_platform AS T2 ON T1.id = T2.platform_id INNER JOIN game_publisher AS T3 ON T2.game_publisher_id = T3.id INNER JOIN game AS T4 ON T3.game_id = T4.id WHERE T4.game_name = 'Counter Force'