The difficulty slider is a great idea, thx for the suggestion. You pointed out an in-game note taking system would be great, so I suppose you missed the fact that there already is one :) You can write on the paper with the explanation (left mouse button to draw, right mouse button to erase). You can see this behaviour on the screenshots and it is even written on the paper itself.
Thanks for the feedback, I will probably add a difficulty slider or something similar in a future update!