<!DOCTYPE html>
<title>Circle shape-outside on floats with percentage radius</title>
<style>
.container {
    font: 40px/1 Ahem, sans-serif;
    line-height: 40px;
    width: 110px;
    height: 40px;
    overflow: hidden;
    white-space: nowrap;
    background-color: red;
    color: green;
}

.circle {
    width: 80px;
    height: 40px;
    background-color: green;
    -webkit-shape-outside: circle(50% at 50% 50%) content-box;
}
</style>

<body>
    <p>You should see a green rectangle. You shouldn't see any red.</p>
<div class="container">
    <div style="float: left; margin-right: 40px;" class="circle"></div>
X
</div>

<div class="container" style="text-align: right">
<div style="float: right; margin-left: 40px;" class="circle"></div>
X
</div>
</body>