body {
  background-color: #0a192f;
}

body::before {
  content: '';
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  background: radial-gradient(600px at var(--x, 50%) var(--y, 50%), rgba(29, 160, 216, 0.15), transparent 80%);
  z-index: 0;
  transition: background 0.2s ease;
}