Arduino Line Following Robot Code (basic calibration)

// Arduino UNO Basic Line Following Robot Code
// Code hosted on https://github.com/Mcspanky93/Line-Follower-Calibration-Buzzer

int sensor1 = A0; //connected to analog 0
int sensor2= A1; // connected to analog 1
int sensor3= A2; // connected to analog 2
int sensor4= A3; // connected to analog 3
int sensorMin1 = 1023;   // minimum sensor value
int sensorMin2 = 1023;
int sensorMin3 = 1023;
int sensorMin4 = 1023;
int sensorMax1 = 0;    // maximum sensor value
int sensorMax2 = 0;
int sensorMax3 = 0;
int sensorMax4 = 0;
int sensorValue1 = 0;  // Placeholder reading value
int sensorValue2 = 0;
int sensorValue3 = 0;
int sensorValue4 = 0;

#include <Servo.h>
 
Servo servo1;
Servo servo2;

void setup()
{
Serial.begin(9600);
// PWM wire on Servo to DO pin on Arduino
servo1.attach(5);
servo2.attach(6);
//Buzzer assignment
pinMode(9, OUTPUT); 
    while (millis() < 5000) {
    tone(9,500,500); //BEGIN CALIBRATION SOUND   
      // Grabs incoming data from the photosensor
    sensorValue1 = analogRead(sensor1);
    sensorValue2 = analogRead(sensor2);
    sensorValue3 = analogRead(sensor3);
    sensorValue4 = analogRead(sensor4);

    // Record the maximum sensor value, and sets as new limit
    if (sensorValue1 > sensorMax1) {
      sensorMax1 = sensorValue1;
    }
    if (sensorValue2 > sensorMax2) {
      sensorMax2 = sensorValue2;
    }
    if (sensorValue3 > sensorMax3) {
      sensorMax3 = sensorValue3;
    }
    if (sensorValue4 > sensorMax4) {
      sensorMax4 = sensorValue4;
    }

    // Record the minimum sensor value, and sets as new limit
    if (sensorValue1 < sensorMin1) {
      sensorMin1 = sensorValue1;
    }
    if (sensorValue2 < sensorMin2) {
      sensorMin2 = sensorValue2;
    }
    if (sensorValue3 < sensorMin3) {
      sensorMin3 = sensorValue3;
    }
    if (sensorValue4 < sensorMin4) {
      sensorMin4 = sensorValue4;
    }
   } 
}

void loop(){        
// Read sensor's collected values:
  sensorValue1 = analogRead(sensor1);
  sensorValue2 = analogRead(sensor2);
  sensorValue3 = analogRead(sensor3);
  sensorValue4 = analogRead(sensor4);
// Maps data to recieved data during calibration period, identifying line
  sensorValue1 = map(sensorValue1, sensorMin1, sensorMax1, 0, 100);
  sensorValue2 = map(sensorValue2, sensorMin2, sensorMax2, 0, 100);
  sensorValue3 = map(sensorValue3, sensorMin3, sensorMax3, 0, 100);
  sensorValue4 = map(sensorValue4, sensorMin4, sensorMax4, 0, 100);
// Keeps data within requested range
  sensorValue1 = constrain(sensorValue1, 0, 100);
  sensorValue2 = constrain(sensorValue2, 0, 100);
  sensorValue3 = constrain(sensorValue3, 0, 100);
  sensorValue4 = constrain(sensorValue4, 0, 100);  
// Averaging the 4 sensors for better stability  
  int INPUT1 = (sensorValue1 + sensorValue2)/2;
  int INPUT2 = (sensorValue3 + sensorValue4)/2;
  int MIDDLE = (sensorValue2 + sensorValue3)/2;

  // Driving logic, servos need to be tested for true stopping point(93 in this case)first
if (MIDDLE > INPUT1 && MIDDLE > INPUT2) {
      servo1.write(0);
      servo2.write(180);
}  
else {
 if (INPUT1 > INPUT2 && INPUT1 > MIDDLE ) { 
      servo1.write(180);
    }
  else if (INPUT2 > INPUT1 && INPUT2 > MIDDLE) {
      servo2.write(0);
    }
  else {
    servo1.write(93);
    servo2.write(93);
  }
}
//Troubling shooting statements to see on serial monitor
  //Serial.print("sensor1:");
  // Serial.println(sensorValue1);
  // Serial.print("sensor2:"); 
  // Serial.println(sensorValue2);
  // Serial.print("sensor3:");
  //Serial.println(sensorValue3);
  // Serial.print("sensor4:");
  // Serial.println(sensorValue4);
  // Serial.print("INPUT1:");
  // Serial.println(INPUT1);
  //Serial.print("INPUT2:");
  //Serial.println(INPUT2);
  //Serial.print("MIDDLE:");
  //Serial.println(MIDDLE);

  // Delay statement, experimentally 10ms seems to be a good update time, faster
  // update time could lead to unstability through photoresistor noise
  delay(10);
}