radiate

int HALF_POS = (NUM_LEDS * 0.5) - 1;

void radiate() {

  zero  = mono[0];
  three = mono[4];
  six   = mono[6];

  leds[HALF_POS] = CRGB(zero, three, six);

  // high frequencies = blue = FAST SPEED
  EVERY_N_MILLISECONDS(11) {
    for (int i = NUM_LEDS; i > HALF_POS; i--) {
      leds[i].blue = leds[i - 1].blue;
    }
  }

  // mid frequencies = green = MEDIUM SPEED
  EVERY_N_MILLISECONDS(30) {
    for (int i = NUM_LEDS; i > HALF_POS; i--) {
      leds[i].green = leds[i - 1].green;
    }
  }

  // low frequencies = red = SLOW SPEED
  EVERY_N_MILLISECONDS(58) {
    for (int i = NUM_LEDS; i > HALF_POS; i--) {
      leds[i].red = leds[i - 1].red;
    }
  }

  // for mirroring to the other half of the strip
  for (int i = NUM_LEDS; i > HALF_POS; i--) {
    leds[HALF_POS - (i - HALF_POS)] = leds[i - 1];
  }

  FastLED.show();
}