Radar CSS

example.html

<div class="radar"></div>

radar.css

  .radar {
  position: relative;
  width: 50px;
  height: 50px;
  border: 2px solid #0f0;
  border-radius: 50%;
  background: 
    repeating-radial-gradient(circle at center, 
      transparent 0%,
      transparent 4%,
      rgba(0, 255, 0, 0.2) 4.5%,
      transparent 10%
    ),
    radial-gradient(circle at center, 
      #002400 0%,
      #000000 80%
    );
  overflow: hidden;
}

.radar::before {
  content: "";
  position: absolute;
  top: 0; left: 0;
  width: 100%; height: 100%;
  border-radius: 50%;
  background: conic-gradient(
    transparent 90%,
    rgba(0, 255, 0, 0.6) 100%
  );
  transform-origin: 50% 50%;
  animation: rotate 2s linear infinite;
}

@keyframes rotate {
  to { transform: rotate(360deg); }
}