#define LED_PIN A0
#define LED_NUM 10
#include "FastLED.h"
CRGB leds[LED_NUM];


void setup() {
 FastLED.addLeds<WS2812, LED_PIN, GRB>(leds, LED_NUM);
 FastLED.setBrightness(50);
 pinMode(A0, OUTPUT);     
}

byte counter = 0;
int8_t dir = 1;
void loop() {
  FastLED.clear();
  leds[counter] = CRGB(255, 242, 0);
  FastLED.show();

  counter+=dir;
   if ((counter == LED_NUM-1) || (counter == 0)) dir=-dir;
 
  delay(200);
}