[CSS] Making Circles

1 - Border Radius
Ex:
.circle {
  background: #456BD9;
  border: 0.1875em solid #0F1C3F;
  border-radius: 50%;
  box-shadow: 0.375em 0.375em 0 0 rgba(15, 28, 63, 0.125);
  height: 5em;
  width: 5em;
}

2 - SVG
Ex:
<svg viewBox="0 0 80 80" width="80" height="80">
  <circle class="circle" cx="40" cy="40" r="38"/>
</svg>

3 - Clip Path
Ex: 
.circle {
  background: #456BD9;
  clip-path: circle(50%);
  height: 5em;
  width: 5em;
}

4 - Radial Gradient
Ex: 
.circle {
  background-image: radial-gradient(circle, #456BD9, #456BD9 66%, transparent 66%);
  height: 5em;
  width: 5em;
}