Consider this a small one, but the Dark pencil has 16 signs or "Drawings". However, there's no way to keep track of which ones you've already used as a means to quickly know which sign does what. And while we can open the wiki-page to read it, that in and of itself shouldn't be needed to look up what does what.
Maybe have a button the player can click to view a list with descriptions to let players know what does what, and if the player can't draw after activating the effect (like drawing a triangle to activate the "On fire" effect) either have a marker next to it or add "Can't draw anything else upon activation" or similar.
On a small side-note, I have seen one doesn't work either so out of the 16 - only 15 work.