Stopwatch(Min&Sec)

#include <LiquidCrystal.h>

// initialize the library by associating any needed LCD interface pin
// with the arduino pin number it is connected to
unsigned long lastOut = 0;
LiquidCrystal lcd(12,11,5,4,8,7);
const int b1 = 2, b2 = 3;
int op = 0; //op=0 for 0 state, op=1 for running state, op=2 for paused state
int m=0,s=0;
int ct=0;
int buttonState;             
int lastButton1State = LOW;
int lastButton2State = LOW;   
unsigned long lastDebounceTime = 0;  
unsigned long debounceDelay = 50;  

void setup() 
{
  Serial.begin(9600);
  pinMode(b1,INPUT); 
  pinMode(b2,INPUT);
  lcd.begin(16, 2);
  lcd.clear();
  lcd.print(" 0 sec");
}

void loop() 
{
  	int reading1 = digitalRead(b1);
  	if (reading1 != lastButton1State)
  	{
    	lastDebounceTime = millis(); // Reset the debouncing timer
  	}
 	if ((millis() - lastDebounceTime) > debounceDelay) // Check if state change has lasted for longer time than debounce delay
  	{
    	if (reading1 != buttonState) 
    	{
      		buttonState = reading1;
      		if (buttonState == HIGH) // Only shift if button is pressed
      		{
      			if (op==1 ||  op==2)
                {
                  op=0;
              	  lcd.setCursor(0,1);
                  lcd.print(" Stop   "); //Stop the timer
                  delay(1000);
            	}
      			else
      			if (op==0)
                {
                  op=1;
                  lcd.setCursor(0,1);
                  lcd.print(" Start  "); //Start the timer
                  delay(1000);
                }
    		}
     	}
    }
  	
   	int reading2 = digitalRead(b2);
  	if (reading2 != lastButton2State)
  	{
    	lastDebounceTime = millis(); // Reset the debouncing timer
  	}
 	if ((millis() - lastDebounceTime) > debounceDelay) // Check if state change has lasted for longer time than debounce delay
  	{
    	if (reading2 != buttonState) 
    	{
      		buttonState = reading2;
      		if (buttonState == HIGH) // Only shift if button is pressed
      		{
      			if (op==1)
      			{
        			op=2;
        			lcd.setCursor(0,1);
        			lcd.print(" Paused "); //Pause the timer
                  	delay(1000);
      			}
      			else
      			if (op==2)
        			op=1;
            }
        }
    }
   	if (op==1)
    {
      lcd.clear();
      s++;//count second
      if (s==60)
      {
        m++;//count minute
        s=0;//reset second
      }
      if (m<1)//print only sec
      {
        lcd.print(" ");
        lcd.print(s);
      	lcd.print(" sec");
      }
      else
      if (m>0)//print min and sec
      {
        lcd.print(" ");
        lcd.print(m);
      	lcd.print(" min ");
        lcd.print(s);
      	lcd.print(" sec");
        
      }
      //output to serial to confirm LCD output
      Serial.print("S=");
      Serial.print(s);
      Serial.print(" M=");
      Serial.println(m);
        
    }
  	if (op==0)
    {
      //reset
      s=0;
      m=0;
      lcd.clear();
  	  lcd.print(" 0 sec "); 
    }
 //reset lastButtonstates for debouncing
 lastButton1State = reading1;
 lastButton2State = reading2;
 delay(1000);//delay 1 sec
  
}