What is the genre of the game "Mario vs. Donkey Kong"?
genre refers to genre_name; game "Mario vs. Donkey Kong" refers to game_name = 'Mario vs. Donkey Kong'
SELECT T1.genre_name FROM genre AS T1 INNER JOIN game AS T2 ON T1.id = T2.genre_id WHERE T2.game_name = 'Mario vs. Donkey Kong'