You can unlock additional modes and courses by satisfying the corresponding requirements.

Mode or Course	How to unlock
Berserk	Unlock Clear area I
Nightmare Area	Finish Area IV
Nightmare Course 1	Gather 80 or more stars in Area I
Nightmare Course 2	Gather 80 or more stars in Area II
Nightmare Course 3	Gather 80 or more stars in Area III
Nightmare Course 4	Gather 80 or more stars in Area IV
Nightmare Course 5	Gather 26 or more stars in Nightmare courses 1-4
Speedster	Finish Area II
Time Records	Finish Area II
Uncle Time	Finish Area III