.ino

#include <FastLED.h>

const auto NUM_LEDS = 30;

CRGB leds[NUM_LEDS];
CRGBSet  left(leds,          0, NUM_LEDS/2);
CRGBSet right(leds, NUM_LEDS-1, NUM_LEDS/2);

void setup() {
  FastLED.addLeds<WS2812B, 6, GRB>(leds, NUM_LEDS);
  FastLED.setBrightness(32);
  FastLED.clear();
}

void loop() {
  for (int i = 0; i < NUM_LEDS/2 - 1; i++) leds[i] = leds[i+1] % 192;

  left[NUM_LEDS/2 - 1] = random8() < 32 ? CRGB::Red : CRGB::Black;

  right = left;

  FastLED.show();
  delay(50);
}