const int lmotor = 3;
const int rmotor = 5;
const int buzzer = 4;
const int sensor = A0;

int sensor_data = 0;
int pwm = 255;

bool flag = false;
bool buzz_flag = false;

void setup(){
  Serial.begin(9600);
  pinMode(lmotor, OUTPUT);
  pinMode(rmotor, OUTPUT);
  pinMode(buzzer, OUTPUT);
  pinMode(sensor, INPUT);

  pwm = 255;
}

void engine(int pwm){
  analogWrite(lmotor, pwm);
  analogWrite(rmotor, pwm);
}

void buzzing(int a, int b, bool buzz_flag){
  if(!buzz_flag){
  digitalWrite(buzzer, HIGH);
  delay(a);
  digitalWrite(buzzer, LOW);
  delay(b);
  }
}

void loop(){
  sensor_data = analogRead(sensor);
  sensor_data = map(sensor_data, 0, 1023, 25, 500);
  Serial.println(sensor_data);

  for(int i = 0; i <= 20; i++){
    if(sensor_data >= 450 && !flag){
      Serial.println("first loop began");
      engine(255);
      buzzing(100, 100, false);
      if(i == 9){
        flag = true;
        Serial.println("flag is true");
      }
    }

    if(sensor_data >= 450 && flag && i < 20){
      if(!buzz_flag){
        buzzing(2000, 0, false);
        delay(100);
        buzzing(0, 0, true);
      }
      for(int j = 255; j >= 0; j--){
        Serial.println("second loop started");
        Serial.println(j);
        engine(j);
        if(j == 0){
         flag = false;
         Serial.println("loop terminated");
         for(;;); 
        }
        delay(100);
      }
    }
  }
}