.lightning-line {
  fill: none;
  stroke: #0ff;  /* ネオンブルー */
  stroke-width: 3;
  stroke-dasharray: 1000;
  stroke-dashoffset: 1000;
  animation: bolt 0.2s linear forwards;
  filter: drop-shadow(0 0 10px #0ff)
          drop-shadow(0 0 20px #0ff)
          drop-shadow(0 0 40px #fff);
}

@keyframes bolt {
  to {
    stroke-dashoffset: 0;
  }
}