No explanation of the darkness. You are unable to win this unless the darkness stops damaging you. Followed your walkthrough, did the bad ending again multiple times but the darkness still hits me and I am unable to get the good ending.
EDIT: thanks, see the pattern (with water, thorns etc.) now. Guess it is more a comment on the walkthrough then – that it would be more clear with a direct statement about avoiding the thorn/darkness note for the good ending as it is a subtle thing easy to miss (especially with the darkness as you don't see darkness before the note).