user: Question: What type of 3D game did Valve Corporation release?
Columns: ['Developer(s)', 'Release date', 'Required OS', 'Genre', 'Type']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['Robot Entertainment , Gas Powered Games', 'August 16, 2011', 'Windows', 'MMORTS', '3D']
SQL:

assistant: SELECT "Genre" FROM "Table" WHERE "Type" = '3D' AND "Developer(s)" = 'Valve Corporation';