I really liked your notes on what you did how and why. Always interesting to see developer notes.
At first, I thought the notebook would show me how to make spells. Then it took a bit for me to figure out the alchemy menu.
Trying to craft new spells and discovering new ingredients is a really fun game mechanic.
When I met the rocky shield enemy, I first thought you have to find a specific spell to overcome the shield because there was no visual effect of doing damage to it.
The boss fight would probably be a bit too difficult if death was not disabled because I got stuck multiple times between the four shadowy enemies in the middle.
A Fullscreen mode would be nice. FYI, itch.io has an option to show a Fullscreen button, but you might need to adjust some export settings for scaling.
Congratulations on publishing your fourth game!