Thanks to the people streaming the game, I can update some level to make them better.

Training Square
Level 3: Adding 2 news enemies to understand directly that every color protects the whole square.
Level 4: Removing one enemy, the shortcut version of this level is too hard compared to the rest of the game

Grassland:
Level 4: Easier to access the rapidity path
Level C: Adding a door to protect the player from blocking themself.

Shivering:
Level 1: Adding a new enemy helping understand a mechanic useful later.
Level 6: Adding a mine to block an idea that is good, but not possible.

Nighttime:
Level 8: Adding a door to make it better to test the possibilities instead of having to restart the level.
Level 9: Making a new way of finishing the level possible.

Quality of life :
-Now the challenges on the world map are icons instead of numbers and when you select them, you can see what is the challenge instead of having to launch the level.
-Every challenge tells you that the level is modified, it'll help the player understand they are playing a version of the base level that forces them to finish the challenge.
-Tips have now the number associated, helping players understand there are multiple tips.
-Removing the cooldown on tips.