<!DOCTYPE html>
<style>
body { margin: 0 }
p {
height: 1200px;
width: 100px;
box-shadow: 0px -100px 100px black;
}
</style>
<p>
<div style="position:absolute; background: white; top: 100px; left: 212px; height: 2px; width: 2px"></div>