Chapter 8: Core

Chapter 8: Core is the eighth chapter of Celeste. This chapter introduces various new features, most notably: the inability to recharge dashes (without using a Diamond, or going through a screen transition), and the Crystal Heart Gate. The Crystal Heart Gate blocks the player from accessing the majority of Chapter 8: Core, until certain conditions are met (see below).

Unlocking
This chapter is unlocked after completing Chapter 7: The Summit/Epilogue. However, a Crystal Heart Gate blocks off the player from most of the chapter's content. The player must collect a certain number of Crystal Hearts to unlock a given side of the chapter, as detailed below:
 * To access the A-Side of this chapter, the player must have obtained at least 4 Crystal Hearts.
 * To unlock the B-Side, the player must have 15 Crystal Hearts, requiring the player to obtain all blue Crystal Hearts and all red Crystal Hearts (minus the one from Chapter 8's B-Side).
 * To access the C-Side, the player must have unlocked all 23 Crystal Hearts (excluding the one from this chapter's C-Side).

Change in Dashing
Chapter 8 features the double dash ability also seen in Chapter 7. However, unlike all previous chapters, landing on the ground restores stamina but no longer restores dashing, requiring the player to change screens or use a Diamond to restore all dashes.

Objects
The first sub-chapter, Start, contains two objects: Spikes and Diamonds. More to come...

Crystal Heart
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Alternate Sides
The B-Side features similar, yet more difficult gimmicks compared to the original chapter. It has more cycle based parts, harder timings and more tight momentum management. The player needs to collect 15 Crystal Hearts in order to access this B-Side. Beating it will unlock C-Sides and Golden Strawberries.

The C-Side features main core gimmicks, however the last section also has a lot of objects from other chapters, such as Dream Blocks, Conveyor-Belt Platforms, Swap Blocks and Clouds. It's also the first and only stage that introduces the Hyper Dashing mechanic. In order to access this C-Side, the player needs to collect 23 Crystal Hearts. Beating it will unlock Variant Mode.

Quotes
More to come...

Speedrunning Record Progression
At the time of writing, the longest running Celeste record ever was Core A 4:07 by Glackum, set on 16 April 2018, which stood for 193 days before being slain by Aurora Dash with Core A 4:04.

Clear (8A):

B-Side (8B):

C-Side (8C): Note: Spirialis' Core C 55 was retracted on 5 September 2018, despite the fact that its legitimacy was not in question. This caused the world record to revert back to Lvl19's Core C 56. On 1 August 2019, he then retracted his first Core C 51 and replaced it with a weaker run. Due to time zone differences, Aurora's 51 occurred earlier in real time than Spirialis' second 51 despite being on the following day, meaning that it did in fact stand as the world record, albeit only for a few hours.

Full Clear:

Major Strategies
8A contains "fireskip", a major skip where a significant section of the level can be bypassed by moving between two counter-rotating strings of fireballs while still in red (hot) mode instead of changing to blue (cold) mode, which makes this particular obstacle much easier. This can be extended to "iceskip", which is used to obtain a berry in a way that also skips that section in full clear runs. This trick, in addition to the fact that 8A contains only five berries (the second fewest behind Reflection) and all other collectibles are mandatory, means that the time difference between 8A clear and full clear runs is much smaller than for any other level.

In both 8A and 8B, there are instances where one has a choice of completing levels in either red mode or blue mode, but usually one path is clearly intended. In 8B, breaking from the intended path saves time in at least two places. Playing the first two rooms of the fourth checkpoint in blue mode instead of red mode, known as "heartskip", saves about 5 seconds, although it has a number of variants which can alter this number. Playing the last two rooms of the level in blue mode is a more aggressive strategy called "blueskip", which saves about 1 second. This causes the level to end in blue mode, which affects the tape room's appearance, although it functions the same as it always does.

In 8C, the heart gate that halts progress unless the player has 23 hearts is in the first room, instead of the third or second rooms in 8A and 8B. While one normally needs to wait for the gate to open, in 8C, one can open the gate, then fall offscreen, killing herself. Because Madeline has not yet left the first room, the timer resets when she respawns. This trick allows one to start with the gate open, saving roughly 5.5 seconds. 8C also has the mythical "TAS strat" in which one obtains great speed at the beginning of the extremely long fourth and final room, maintaining this speed through a large proportion of the screen. This has never been done without slowing the game down or using TAS tools, but is believed that this strategy will eventually become viable in such speedruns.

Trivia

 * While 7A and 7B are the longest A- and B-Sides, 8C is the longest C-Side. Even so, it is still slightly shorter than the shortest non-C-Side, which is 1A.