How to change character?

[Great White Buffalo]

I just unlocked the girl with the katana (Float?), and now I have to play as her every level. How do I change back to Spark?

[kirahari_chi]

there is no way, bro, the second part of the game is fully about float

[DJsquare3 (Nebula)]

You equip her as a power into one of your 4 power slots in the shop (D pad on controler or 1234 on Mouse and Keyboard) Then just press the button to switch between them.
Float is entirely optional but she is really good in some situations.

[Fluppie >:)]

How did you end up doing that but not figuring out how to change back? Everytime you start a new stage you start as Spark. Not to mention changing back is the same method is how you change to Float in the first place.