Celeste

At the very start of section 3, get the feather that is to your left and take it all the way to the top right. Instead of going through to the next room, break the floor below you to reveal another feather. Take that one straight up and climb the walls to get to another feather. Now take that feather all the way to the left side and you'll see an opening to go through. Go through there and follow it until you're in the room with the colored diamonds and weird statue.

These colors correspond with patterns from the first crystal heart on Chapter 1. You need to input codes using these colors to light four flames in the room by dashing in certain directions. Here are the directions you need to dash in.

Code 1
Up, left, downright, upright, left, upleft.

Code 2
Up, right, downleft, upleft, right, upright

Code 3
Down, left, upright, downright, left, downleft

Code 4
Down, right, upleft, downleft, right, downright

When all four flames are lit, your crystal heart will appear. Smash through it to get your achievement.

Also, here is a video for your visual learners.

Hey everyone, just a quick video showing where to find both the Cassette Tape and the Crystal heart for Chapter 6. Biggest thing to know is the Heart follows the same color pattern as in Chapter 1.

1- Up, Left, Down-Right, Up-Right, Left, Up-Left
2- Up, Right, Down-Left, Up-Left, Right, Up-Right
3- Down, Left, Up-Right, Down-Right, Left, Down-Left
4- Down, Right, Up-Left, Down-Left, Right, Down-Right

Hope the video helps!