#include <FastLED.h> // https://github.com/FastLED/FastLED

#define LDR A0 // analog output
#define LED_NUM   10 // number of LEDs or WS2812
#define BAR_PIN   3 // LEDs starting pin
#define PIX_PIN   2 // WS2812 pin
#define MAXBRIGHT 255
CRGB pixleds[LED_NUM]; // create FastLED object

void setup() {
  FastLED.addLeds<WS2812B, PIX_PIN, GRB>(pixleds, LED_NUM); // initialize FastLED object
  FastLED.setBrightness(MAXBRIGHT);
  FastLED.clear();
  FastLED.show();

  for (int i = 0; i < LED_NUM; i++) { // initialize the LED pins
    pinMode(BAR_PIN + i, OUTPUT);
  }
}

void loop() {
  float ldr = analogRead(A0); // read the LDR
  int lux = map (ldr, 1015, 8, 1, 10); // map LDR to 10 LEDs (1015 and 8 are simulation MAX and MIN) 
  for (int i = 0; i < lux; i++) { // counting zero to LDR map
    pixleds[i]  = CRGB(lux * 25.5, 0, 255 - (lux * 25.5)); // color WS2812 from BLU to RED
    FastLED.show();
    digitalWrite(BAR_PIN + i, HIGH); // light LEDs 
  }
  for (int i = lux; i < LED_NUM; i++) { // counting from LDR map to MAX/10
    pixleds[i]  = CRGB::Black; // turn WS2812 off
    FastLED.show();
    digitalWrite(BAR_PIN + i, LOW); // turn LEDs off
  }
}