It's been a long time since I played Picross. I liked how they combined the hidden images with a small plot in the form of a graphic novel that gave consistency to the type of drawings when choosing the theme of magic and even defined their role in a world of magic which makes one have curiosity about the world where those little witches live.
I'm not very experienced in those types of games but the relaxing music and general tone of the game make it quite relaxing as well as entertaining.