Every level has a clean solution that doesn't need extra precise timing. I invested a lot of time to make the game as less frustrating as I could. Sadly it'll never be perfect!
But thanks to the people streaming the game, I detected some spots that may make the player feel what he's doing is the right answer while it's not (thus, generating frustration).
Level C Grassland :
Adding some doors preventing player from blocking the mirrors and having to reset the level.
Level 7 Shivering Challenge :
Adding a mine to stop players trying to force their way through the blue shots and timing a suicide. It feels too much for a good solution while being extremely difficult. All the puzzle have a clean solution that doesn't need extra dodge skills.
Debug
Level 8 Challenge Nightime: Removing one enemy.
Using the validate button in the pause menu does not move your square anymore.
The controller cancel button works in the pause menu on the resume button.