<!DOCTYPE HTML>
<p>Below there should be a solid green circle with a black border and no red.</p>
<br>
<div style="position:relative; z-index:1; overflow:hidden; margin-top:100px; width:200px; height:200px; border-radius:50%; border:10px solid black; background:red;">
    <div style="will-change: transform; width:300px; height:300px; margin-left:-50px; margin-top:-50px; background:green;"></div>
</div>