Successfully complete Level 9A or 9B (Iceberg Base or Sea of Clouds)
with at least a four star rank in Arcade or Score Attack mode to play
the Clouds Of Twilight level instead of the Sea Of Twilight level that
normally follows. Note: To get a star, complete a stage with at least
50% shot down. You will lose one star if you are shot down. You will
lose all stars if you have to use a continue.