---

#define PHOTO A0

#define RED 4
#define GREEN 2
#define YELLOW 3

void setup()
{
  Serial.begin(9600);

  pinMode(PHOTO, INPUT);

  pinMode(RED, OUTPUT);
  pinMode(GREEN, OUTPUT);
  pinMode(YELLOW, OUTPUT);
}

void loop()
{
  int light = analogRead(PHOTO);
  Serial.println(light);
  delay(200);

  if (light < 300)
  {
    // Света нет
    digitalWrite(RED, HIGH);
    digitalWrite(GREEN, LOW);
    digitalWrite(YELLOW, LOW);
  }
  else if (light < 500)
  {
    // Половина света
    digitalWrite(RED, LOW);
    digitalWrite(GREEN, HIGH);
    digitalWrite(YELLOW, LOW);
  }
  else
  {
    // Весь свет
    digitalWrite(RED, LOW);
    digitalWrite(GREEN, LOW);
    digitalWrite(YELLOW, HIGH);
  }
}