Easy
Block length:  4 numbers.  2 phases before boss.
Normal
Block length:  4 to 5 numbers.  2 phases before boss.
Hard
Block length:  5 numbers.  3 phases before boss.
Expert
Block length:  4 to 6 numbers.  4 phases before boss.
2 Hard
Block length:  5 to 6 numbers.  5 phases before boss.
Extreme
Block length:  5 to 7 numbers.  6 phases before boss.
xtreme
Block length:  6 to 8 numbers.  7 phases before boss.
Impossible
Block length:  5 to 8 numbers.  8 phases before boss.