How does Sora travel in Re:Coded?

[Burning Blaze]

Just a quick question.How does Sora travel to different worlds in this? Are the gummi ship segments in it? Sorry if this has already been answered.

 

[Dark Wing]

once you get far enough in the story and have been to a few worlds, you can go to previous worlds from the save points. until that point you move to the next world right after beating the boss of the current world automatically