Alternate sides

Alternate sides (namely B-Sides and C-Sides) of a chapter are essentially harder but shorter versions of this chapter. They exist in every chapter except Prologue, Epilogue and Farewell.

In alternate sides, a remix of the chapter's music is used. These remixes are known as Celeste B-Sides, although the exact same soundtrack plays in C-Sides as well.

Alternate sides do not have any Red Strawberries, but Golden Strawberries can be found and collected there if they have been unlocked and the alternate side has been completed before.

Additionally, alternate sides of all levels will be instantly unlocked when Cheat Mode is enabled in the save file.

B-Sides

A Red Crystal Heart

A B-Side for a given chapter can be unlocked by collecting a Cassette Tape in the A-Side of the level. It can then be accessed right away, even if the A-Side is not completed yet, and it is possible to unlock the new chapter by completing the B-Side instead. This is commonly used in speedruns to save time since 5B and 6B are shorter than their A-side counterparts.

Like A-Sides, B-Sides are segmented into checkpoints.

At the end of each B-Side is a Cassette Block Room, the only room in the B-Side having Cassette Block, and which ends with a Red Crystal Heart. Collecting the Red Crystal Heart by dashing into it ends the B-Side.

Completing all B-Sides except Core B-Side is required to unlock the Crystal Heart Gate in Farewell and 8B.

1B  •  2B  •  3B
4B  •  5B  •  6B
7B  •  8B

C-Sides

A Yellow Crystal Heart

C-Sides are unlocked after completing 8B, which, in turn, requires completion of all B-Sides. They are significantly shorter than A-Sides and B-Sides, consisting of just 3-4 rooms and with no checkpoints. The rooms themselves, however, are longer and more difficult compared to those of A- and B-Sides.

C-Sides end with a Yellow Crystal Heart. Core C-Side unlocks only if all other C-Sides had been completed.

1C  •  2C  •  3C
4C  •  5C  •  6C
7C  •  8C