Прелоадер на CSS

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

html, body {
  width: 100%;
  height: 100%;
}

body {
  background: #0b0b14;
  overflow: hidden;
}

.container {
  position: absolute;
  margin: auto;
  top: 0;
  left: 0;
  bottom: 0;
  right: 0;
  width: 400px;
  height: 400px;
}
.container .circle {
  position: absolute;
  margin: auto;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
  border-radius: 50%;
  background: rgba(138, 43, 226, 0.02);
}
.container .circle:nth-of-type(1) {
  width: 200px;
  height: 180px;
  animation: rt 6s infinite linear;
  box-shadow: 0 0 1px 0 blueviolet, inset 0 0 10px 0 blueviolet;
}
.container .circle:nth-of-type(2) {
  width: 180px;
  height: 200px;
  animation: rt 10s infinite linear;
  box-shadow: 0 0 1px 0 darkviolet, inset 0 0 10px 0 darkviolet;
}
.container .circle:nth-of-type(3) {
  width: 210px;
  height: 190px;
  animation: rt 5s infinite linear;
  box-shadow: 0 0 1px 0 darkmagenta, inset 0 0 10px 0 darkmagenta;
}
.container .circle:nth-of-type(4) {
  width: 190px;
  height: 210px;
  animation: rt 15s infinite linear;
  box-shadow: 0 0 1px 0 magenta, inset 0 0 10px 0 magenta;
}

@keyframes rt {
  100% {
    transform: rotate(360deg);
  }
}