* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  background: #000;           /* common dark background for this effect */
}

.loader {
  width: 300px;
  height: 300px;
  border-radius: 50%;
  border: 6px solid #0ff;
  box-shadow: inset 0 0 0px #0ff;
  animation: load 2s linear infinite alternate;
}

@keyframes load {
  100% {
    box-shadow: inset 0 0 150px #0ff;
    filter: hue-rotate(360deg);
  }
}