I wonder if there is a GZDoom mod where you can "draw" in something like a canvas.
Or like MSPaint in GZDoom, where the drawings can even be put in wall textures like graffiti in some games.
Or if you have minigames where you have to draw specific shapes (Or at least "close enough" shapes) for something to happen like drawing a pentagram to summon demons.
Bit of a reference: This newgrounds game revolving around using your mouse to draw shapes to use abilities and shit.