To unlock the Crystal Heart in Chapter 5: Mirror Temple of Celeste, follow this detailed step-by-step guide:

Step 1: Obtain the Key
Begin your adventure by locating the key that is situated above the statue in the level. This key is crucial as you will need it to unlock a hidden door later in the process.

Step 2: Reach the Room Beneath the Statue
Once you have secured the key:
– Proceed to the room directly beneath the statue, which you can find on the right side.
– Utilize the red bubbles found in this area to navigate through.
– Start by jumping into the first red bubble, allowing yourself to soar across the screen to the right.
– It’s important that you do not enter the door at the end of this path. Instead, opt for the second red bubble, which will let you dash upwards to the second platform as you make your way back. This maneuver will grant you access to a secret path that lies above the door.

Step 3: Navigate the Secret Path and Break the Brown Block
After you’ve entered the secret path:
– Follow through the long hallway until you reach the next room.
– Here, make your way to the bottom of the room and locate a brown block on the floor.
– Smash through this block, which will now allow you to access a locked door using the key you found earlier.

Step 4: Enter the Crystal Heart Room and Use Momentum to Reach It
Inside the room where the Crystal Heart is located:
– You will find that this area is dimly lit, and it requires careful movement along the edges.
– Engage with the moving blocks available and use them to gain momentum:
– Begin by dropping down to the first moving block, then dash to launch yourself across the room towards a central platform.
– Jump onto the subsequent moving blocks and continue climbing up the right side of the room.
– Eventually, hop onto another moving block and from there, navigate to the stationary platforms.
– Make your way across these platforms to access the Crystal Heart.

Helpful Tips
– Remember that the moving platforms on tracks propel to the other side when you dash onto them. This momentum is key to reaching areas that would otherwise be unattainable.

Conclusion
To successfully unlock the Crystal Heart in Chapter 5: Mirror Temple, you must meticulously follow these steps: acquire the key, navigate through red bubbles to find a secret path, break the brown block to unlock the door, and skillfully use momentum from the moving platforms to reach the Crystal Heart. Happy climbing!