Comment by skgough
this is most likely due to the absolute positioning. position: absolute will use the top-left corner of the closest ancestor that is "positioned" as the origin for it's layout [1]. If you want that origin to be the top-left corner of the viewport, use position: fixed.
[1] https://developer.mozilla.org/en-US/docs/Web/CSS/Containing_...
In addition to `position: fixed`, shouldn't it be top, left, height, width, instead of top, left, bottom, right? In the second case, it would follow the top and left instructions then take the necessary amount of space, ignoring right and bottom?