body:before {
  content: '';
  position: fixed;
  left: 0; top: 0;
  width: 100vw; height: 100vh;
  pointer-events: none;
  z-index: 9999;
  opacity: 0.3;
  background: url('https://grainy-gradients.vercel.app/noise.svg');
  animation: shakeNoise 0.7s steps(2) infinite;
}

@keyframes shakeNoise {
  0% { background-position: 0 0; }
  100% { background-position: 100px 100px; }
}