Complete the indicated task to unlock the corresponding set of levels.

Levels 11 to 20: Complete any map with a "10" difficulty setting.
Levels 21 to 30: Complete any map with a "20" difficulty setting.
Levels 31 to 40: Complete any map with a "30" difficulty setting.
Levels 41 to 50: Complete any map with a "40" difficulty setting.
Levels 51 to 60: Complete any map with a "50" difficulty setting.