Fun Arduino Stopwatch

//STOPWATCH by Arduino Makers
int nummin=0;
int numsec=0;
int numdigit[3] = { 0,0,0 };
int digit = 0;
int tick = 0;
int stopwatch = 0; // 0:stop(reset), 1:go, 2:pause 
int stateflag = 0;
int btn = LOW;
int btntick = 0;
int startflag = 1;

void setup() {
  
  pinMode(2,OUTPUT);
  pinMode(3,OUTPUT);  
  pinMode(4,OUTPUT);
  pinMode(5,OUTPUT);
  pinMode(6,OUTPUT);
  pinMode(7,OUTPUT);
  pinMode(8,OUTPUT); 
  pinMode(9,OUTPUT);
  pinMode(10,INPUT);
  pinMode(11,OUTPUT);
  pinMode(12,OUTPUT);
  pinMode(13,OUTPUT);
  digitalWrite(11,LOW);
  digitalWrite(12,LOW);
  digitalWrite(13,LOW);

}

void displayStart()
{
    int data[7][2] = { {10,0},{10,1},{10,2},{3,2},{2,1},{1,0},{10,1} };

    for(int i=0;i<7;i++){
      displayNumber(data[i][0],data[i][1]);
      delay(500);
    }

    startflag=0;  
}

void loop() 
{
  // put your main code here, to run repeatedly:

  if(startflag==1){
    displayStart();
  }
  
  if(btntick==0){
    btn = digitalRead(10);    
    if(btn==HIGH){
      displayNumber(10,1);
      delay(1000);     
      if(stopwatch==0)     stopwatch=1;
      else if(stopwatch==1) stopwatch=2;
      else if(stopwatch==2)  stopwatch=0;
    }
  }
  btntick++;
  if(btntick>=20){
      btntick=0;
  }

  displayNumber(numdigit[digit],digit);
  delay(5);

  digit++;
  if(digit>2) digit=0;  

  if(stopwatch==1){
     tick++;
     if(tick>=200){
       tick=0;
       numsec++;
       if(numsec>=60){
          numsec=0;
          nummin++;
          if(nummin>9){
            nummin=0;
            numsec=0;
            stopwatch=0;
          }
       }
       divideTimeTo3Digit(nummin,numsec);
     }
  }else if(stopwatch==2){
    stateflag=1;     
  }else if(stopwatch==0){
    if(stateflag==1){
      nummin=0;
      numsec=0;
      divideTimeTo3Digit(nummin,numsec); 
      stateflag=0;
    }
  }  
}

void divideTimeTo3Digit(int m,int s)
{
  numdigit[2] = s%10;
  numdigit[1] = s/10;
  numdigit[0] = m;  
}

void divideNumberTo3Digit(int n)
{
  numdigit[2] = n % 10;
  numdigit[1] = (n / 10) % 10 ;
  numdigit[0] = n / 100;
}

void displayNumber(int n,int idx)
{
  turnOnDigit(idx);
  displayCharacter(n);
}

void turnOnDigit(int idx)
{
    switch(idx){
      case 0 : digitalWrite(11,LOW);
               digitalWrite(12,HIGH);
               digitalWrite(13,HIGH);
               break;
      case 1 : digitalWrite(11,HIGH);
               digitalWrite(12,LOW);
               digitalWrite(13,HIGH);
               break;
      case 2 : digitalWrite(11,HIGH);
               digitalWrite(12,HIGH);
               digitalWrite(13,LOW);
               break;
    }
}

void displayCharacter(int n)
{
  if((n<0)||(n>10)) return;
  
  int chartable[11][7] = { { HIGH,HIGH,HIGH,HIGH,HIGH,HIGH,LOW  }, //0
                           { LOW ,HIGH,HIGH,LOW ,LOW ,LOW ,LOW  }, //1
                           { HIGH,HIGH,LOW ,HIGH,HIGH,LOW ,HIGH }, //2
                           { HIGH,HIGH,HIGH,HIGH,LOW ,LOW ,HIGH }, //3
                           { LOW ,HIGH,HIGH,LOW ,LOW ,HIGH,HIGH }, //4
                           { HIGH,LOW ,HIGH,HIGH,LOW ,HIGH,HIGH }, //5
                           { HIGH,LOW ,HIGH,HIGH,HIGH,HIGH,HIGH }, //6
                           { HIGH,HIGH,HIGH,LOW ,LOW ,LOW ,LOW  }, //7
                           { HIGH,HIGH,HIGH,HIGH,HIGH,HIGH,HIGH }, //8
                           { HIGH,HIGH,HIGH,HIGH,LOW ,HIGH,HIGH }, //9
                           { LOW ,LOW, LOW, LOW, LOW ,LOW ,HIGH } }; //- 

  for(int i=0;i<7;i++){
    digitalWrite(2+i,chartable[n][i]);
  }
}