int leds []={12,8,7,4};
int ldr=A0;
int x;
int sensor=0;
int buzzer=2;
int note []={523,494,440,392};

void setup(){
  Serial.begin(9600);
  for(x=0;x<=3;x++){
    pinMode(leds[x], OUTPUT);
  }
  pinMode(ldr, INPUT);
}

void loop(){
  sensor=analogRead(ldr);
  delay(200);

  sensor=constrain(sensor,0,255);

if(sensor < 100){
  digitalWrite(leds[0], HIGH);
  tone(buzzer,note[0], 200);
    }
else if(sensor >=100 && sensor <150){
  digitalWrite(leds[2], HIGH);
  tone(buzzer,note[1], 200);
}
else if(sensor >=150 && sensor <200);{
  digitalWrite(leds[2], HIGH);
  tone(buzzer,note[2], 200);
}
else if(sensor >=200){
  digitalWrite(leds[3], HIGH);
  tone(buzzer,note[3], 200);
}
delay(500);
  for(x=0;x<=3;x++){
    digitalWrite(leds[x], LOW);
  }
  noTone(buzzer);
}