#include <Adafruit_NeoPixel.h>

Adafruit_NeoPixel hv(20, 12, NEO_GRB + NEO_KHZ800);
int k[] = {0, 5, 10, 15};
unsigned long cs = 0;
unsigned long tiem = 1000;

void setup() {
  Serial.begin(9600);
  hv.begin();
  pinMode(12, OUTPUT);
  Serial.println("Aky je advent: od 1-4 ");
}

void loop() {
  if (Serial.available()) {
    int advent = Serial.parseInt();
    if (cs < millis() - tiem) {
      for (int i = 0; i < 20; i++) {
        bool isCandle = (i == 0 || i == 5 || i == 10 || i == 15);

        if (isCandle && i < advent * 5) {
          hv.setPixelColor(i, hv.Color(255, 255, 0));
        } else {
          for(int z = 0;z < 21; z++) {
            if(z != 0 && z != 5 && z != 10 && z != 15) {
          hv.setPixelColor(z, hv.Color(0, 255, 0));
            }
        }
        }
      }
      hv.show();
       cs = millis();
    }
  }
}