This debug UI has been surprisingly handy over the last few days. I'm able to visualize a parse tree even after it's been flattened, just using color transparency. All I'm doing is painting all the rects that contain the mouse cursor. Since the color is transparent, it doesn't matter what order they're in. (The larger rects actually come later; they're fall-backs if a more fine-grained rect isn't found.)

Welcome to the world of moldable development!

Oh I've been here for a while 😄