Awesome game!! Lovely art, the style really suits the storytelling and mythological aspects! It's like an old book c: Definitely got stuck at times, and had to look up multiple walkthroughs haha
Spoilers below for the things I struggled with in case anyone else needs help!
For the sun puzzle, yellow lights means correct colours in the correct place, but it does not indicate which one is correct, you have to figure that out. Grey means a correct colour in the wrong place.
For the false books, use the same colour to letter key you did for the two doors in the cavern. You find the combination using the OTHER key in the sun door (this gave me so much trouble kdhfgkdg)
For the second ending, touch the living statue with the eye and collect the horn pieces to use as offerings instead of the hydra thorns c: