Jason Coon's modified lighning

void lightning2() {
  // The first "flash" in a bolt of lightning is the "leader." The leader
  // is usually duller and has a longer delay until the next flash. Subsequent
  // flashes, the "strokes," are brighter and happen at shorter intervals.

  FastLED.clear();

  ledstart = random8(NUM_LEDS);           // Determine starting location of flash
  ledlen = random8(NUM_LEDS-ledstart);    // Determine length of flash (not to go beyond NUM_LEDS-1)

  const uint8_t frequency = 50; // controls the interval between strikes
  const uint8_t flashes = 12;    // the upper limit of flashes per strike

  static uint8_t dimmer = 1;
  static uint8_t flashCount = flashes;
  static uint8_t flashCounter = 0;

  static uint32_t delayMillis = 0;
  static uint32_t delayStart = 0;

  static bool flashing = true;

  // bail, if we haven't waited long enough
  if (millis() < delayMillis + delayStart)
    return;

  flashing = !flashing;

  if (flashCounter >= flashCount) // if we've finished the current set of flashes, clear the display and wait a bit
  {
    flashCounter = 0;
    fill_solid(leds+ledstart,ledlen, CRGB::Black); // clear the display
    delayMillis = random8(frequency) * 130;
    delayStart = millis();
    return;
  }

  if (flashCounter == 0) dimmer = 5; // the brightness of the leader is scaled down by a factor of 5
  else dimmer = random8(1, 3);      // return strokes are brighter than the leader

  if (flashing)
  {
    fill_solid(leds+ledstart, ledlen, CHSV(255, 0, 255 / dimmer));
    delayMillis = random8(4, 10);
    delayStart = millis();
  }
  else
  {
    fill_solid(leds+ledstart, ledlen, CRGB::Black); // clear the display
    delayMillis = 50 + random8(100);
    if (flashCount == 0) delayMillis += 150; // longer delay until next flash after the leader
  }

  flashCounter++;

}