Write SQL query to solve given problem: What is the genre of the game titled '999: Nine Hours, Nine Persons, Nine Doors' ?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T2.genre_name FROM game AS T1 INNER JOIN genre AS T2 ON T1.genre_id = T2.id WHERE T1.game_name = '999: Nine Hours, Nine Persons, Nine Doors'