<style>
div {
  margin: 10px;
  font-size: 20px;
  display: inline-block;
  font-family: Ahem;
}

span {
  outline: 4px solid blue;
}
</style>
<div><span>XXXX</span></div>
<div><span style="border-radius: 10px;">XXXX</span></div>
<div><span style="border-radius: 10px; outline-offset: 4px;">XXXX</span></div>
<div><span style="border-radius: 1px 5px 10px 15px; outline-offset: 4px;">XXXX</span></div>