There should be many teal squares in a horizontal line touching either side of the canvas/viewport, and the squares should be vertically aligned to be between the HTML box's blue border and the BODY box's green border. Note that there should be one tile EXACTLY horizontally centred across the viewport, so that is is EXACTLY above the purple square that appears at the top of the inner BODY box.

THE TEAL TILES SHOULD NOT BE CLIPPED BY THE HTML BOX'S BORDERS!