<div class="box"></div>

:root {
  --r: 2em;
}

body {
  width: 100vw;
  height: 100vh;
  display: flex;
  justify-content: center;
  align-items: center;
}
.box {
  position: relative;
  min-width: 15em;
  max-width: 15em;
  min-height: 10em;
  outline: 2px solid;
  overflow: hidden;
  
  &::before {
    content: '';
    position: absolute;
    padding: var(--r);
    box-shadow: 0 0 7px #b53;
    background: #95a;
    margin: calc(var(--r) * -1);
    border-radius: 50%;
  }
}