What was the minimum operating system required by Stunlock Studios' game?
CREATE TABLE table_name_91 (
    required_os VARCHAR,
    developer_s_ VARCHAR
)
SELECT required_os FROM table_name_91 WHERE developer_s_ = "stunlock studios"
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What was the minimum operating system required by Stunlock Studios' game? ### Input: CREATE TABLE table_name_91 (
    required_os VARCHAR,
    developer_s_ VARCHAR
) ### Response: SELECT required_os FROM table_name_91 WHERE developer_s_ = "stunlock studios"