How to Design A Solar Tracker Robot With Arduino

#include <Servo.h> 
 
Servo tracker;  // create servo object to control a servo 
int eastLDRPin = 0;  //Assign analogue pins
int westLDRPin = 1;
int eastLDR = 0;   //Create variables for the east and west sensor values
int westLDR = 0;
int error = 0;
int calibration = 10;  //Calibration offset to set error to zero when both sensors receive an equal amount of light
int trackerPos = 90;    //Create a variable to store the servo position

void setup() 
{ 
  tracker.attach(9);  // attaches the servo on pin 11 to the servo object
  Serial.begin(9600);
   tracker.write(90);
   delay(5000);
} 
 
 
void loop() 
{ 
  eastLDR = calibration + analogRead(eastLDRPin);    //Read the value of each of the east and west sensors
  westLDR = analogRead(westLDRPin);
  error = eastLDR - westLDR;          //Determine the difference between the two sensors.
  if(error>15)        //If the error is positive and greater than 15 then move the tracker in the east direction
  {
   
    tracker.write(180);              // tell servo to go to position in variable 'pos' 
    delay(500);                       // waits 15ms for the servo to reach the position 
  
  }
 else if(error<-15)  //If the error is negative and less than -15 then move the tracker in the west direction
  {
                   
    tracker.write(0);              // tell servo to go to position in variable 'pos' 
    delay(500);                       // waits 15ms for the servo to reach the position 
   }
         
  Serial.print(eastLDR);
  Serial.print("   ");
  Serial.print(westLDR);
  Serial.print("   ");
  Serial.println(error);
  delay(500);
}