Level 2 mode:
————-
Successfully complete all eight levels on the Level 1 difficulty to
unlock the Level 2 difficulty.
Level 3 mode:
————-
Successfully complete all eight levels on the Level 2 difficulty to
unlock the Level 3 difficulty.
Level 2 mode:
————-
Successfully complete all eight levels on the Level 1 difficulty to
unlock the Level 2 difficulty.
Level 3 mode:
————-
Successfully complete all eight levels on the Level 2 difficulty to
unlock the Level 3 difficulty.