How Fast Are You? (arcade game)

int flashing = 1;
int btn;



void setup ()
{
  pinMode (4,OUTPUT);
  pinMode (5, OUTPUT);
  pinMode (6, OUTPUT);
  pinMode (7, OUTPUT);
  pinMode (8, OUTPUT);
  pinMode (9, OUTPUT);
  pinMode (10, OUTPUT);
  pinMode (11, OUTPUT);
  pinMode (12, OUTPUT);
  pinMode (13, OUTPUT);
}

void loop ()
{
  if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (4, HIGH);
    
    }
  else
  {
 digitalWrite (4, HIGH);
 delay (10);
 digitalWrite (4, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (5, HIGH);
    
    }
  else
  {
 digitalWrite (5, HIGH);
 delay (10);
 digitalWrite (5, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (6, HIGH);
    
    }
  else
  {
 digitalWrite (6, HIGH);
 delay (10);
 digitalWrite (6, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (7, HIGH);
    
    }
  else
  {
 digitalWrite (7, HIGH);
 delay (10);
 digitalWrite (7, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (8, HIGH);
    
    }
  else
  {
 digitalWrite (8, HIGH);
 delay (10);
 digitalWrite (8, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (9, HIGH);
    
    }
  else
  {
 digitalWrite (9, HIGH);
 delay (10);
 digitalWrite (9, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (10, HIGH);
    
    }
  else
  {
 digitalWrite (10, HIGH);
 delay (10);
 digitalWrite (10, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (11, HIGH);
    
    }
  else
  {
 digitalWrite (11, HIGH);
 delay (10);
 digitalWrite (11, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (12, HIGH);
    
    }
  else
  {
 digitalWrite (12, HIGH);
 delay (10);
 digitalWrite (12, LOW);
 delay (10);
  }
  }
   if(flashing==1)
  {
    btn=digitalRead(3);
    if(btn==LOW)
    {
      flashing=0;
       digitalWrite (13, HIGH);
    
    }
  else
  {
 digitalWrite (13, HIGH);
 delay (10);
 digitalWrite (13, LOW);
 delay (10);
  }
  }
 
 
 
}