100% completion:
     Unlock  all  balls  and  music;  finish  all bonus stages, hidden
stages,  and  the  45 normal stages in both standard and Mirror modes.
Before you've all 20 balls, always try to gain a trophy in the stages.

Unlock bonus stages:
     Get 25 gold trophies to unlock 5 bonus stages.
Note: The gold trophies are also available in Mirror mode. 

Hidden stages:
     Pick  up all 45 green crystals to unlock all hidden stages. There
are  14 of total hidden stages. You can find a hidden green crystal on
each normal stage. Collect them to unlock the hidden stages.

Unlock 15th hidden stage:
     Finish all 5 bonus stages.

Unlock all music:
     Finish all stages.

Unlock Mirror mode:
     Finish all 45 normal stages.

Get 20 balls:
     Finish the all 45 normal stages and 15 hidden stages.

Unlock Car Crush ball:
     Finish the 1st Mirror mode stage and pick up the yellow gem.

Unlock Galaxy ball:
     Finish the 1st Night Zone stage and pick up the yellow gem.

Unlock UFO ball:
     Finish the final Mirror mode stage and pick up the yellow gem.

Unlock Flash ball:
     Finish the final normal mode stage and pick up the yellow gem.