Complete the indicated task to unlock the corresponding difficulty setting.

All Episodes (Impossible and Legendary): Complete Episode 6 under the Very Hard difficulty setting.
Episode 1 (Hard): Complete Episode 2.
Episode 1 (Very Hard): Complete Episode 6 under the Hard difficulty setting.
Episode 2 (Hard): Complete Episode 1 under the Hard difficulty setting.
Episode 2 (Very Hard): Complete Episode 1 under the Very Hard difficulty setting.
Episode 3 (Hard): Complete Episode 5.
Episode 3 (Very Hard): Complete Episode 2 under the Very Hard difficulty setting.
Episode 4 (Hard): Complete Episode 3 under the Hard difficulty setting.
Episode 4 (Very Hard): Complete Episode 3 under the Very Hard difficulty setting.
Episode 5 (Hard): Complete Episode 4 under the Hard difficulty setting.
Episode 5 (Very Hard): Complete Episode 4 under the Very Hard difficulty setting.
Episode 6 (Hard): Complete Episode 6.
Episode 6 (Very Hard): Complete Episode 5 under the Very Hard difficulty setting.