did a quick resketch of your box with buttons.
I like to weight the lines heaviest at the bottom and sides. Try more cross contour lines to show form. Get into the habit of putting down a quick axis before you draw any ellipse that needs to be oriented to something else.
remember, if your tool doesn’t allow line weight variation with pressure changes, like a pencil, you’re going to have to lay down multiple passes to get a heavier line.
