int ldr;

void setup() {
  Serial.begin(9600);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
}

void loop() {
  ldr = analogRead(A1);
  Serial.println(ldr);
  
  if(ldr<200){
    digitalWrite(3, LOW);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    digitalWrite(6, LOW);
  }
  else if(ldr >=200 && ldr <300){
    digitalWrite(3, HIGH);
    digitalWrite(4, LOW);
    digitalWrite(5, LOW);
    digitalWrite(6, LOW);
  }
  else if(ldr >=300 && ldr <400){
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, LOW);
    digitalWrite(6, LOW);
  }
  else if(ldr >=450 && ldr <600){
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    digitalWrite(6, LOW);
  }
  else if(ldr >=600){
    digitalWrite(3, HIGH);
    digitalWrite(4, HIGH);
    digitalWrite(5, HIGH);
    digitalWrite(6, HIGH);
  }
  delay(10);
}