How do I play adventure mode?

[icor1031]

I choose a stage, play it through, and it says "stage clear."
However, nothing changes. It doesn't give me a flag, or on ones where there was a flag - the flag doesn't disappear.

How do I progress?

 

[PersonallyIPreferDair]

All you need to do is choose the next stage. The only reason why there isn't a flag on the previous one is because you didn't get every trophy or discover every room.

 

[icor1031]

Do I need to get them all in order to progress?

 

[shrooby]

A flag appears on a level when you have not broken open every golden item box, or you have not gone through every door. Doing this makes a crown-like thing appear on the level. (The Midair Stadium is guaranteed to have this symbol upon completion as there are no doors to enter or golden item boxes.) Getting the crown-like symbol is not required to go through adventure mode, it is only needed to get 100%.

 

[icor1031]

EDIT: Miss-read earlier.

I'll try that, thanks.