Arduino-HomeWork-01-traffic light

#define HR_LED _BV(2)
#define HY_LED _BV(3)
#define HG_LED _BV(4)
#define VR_LED _BV(5)
#define VY_LED _BV(6)
#define VG_LED _BV(7)

#define SW1 _BV(1)
#define SW2 _BV(2)
#define SW3 _BV(3)

int timer=0;
byte mode;

void setup()
{
  DDRD |= (HR_LED | HY_LED | HG_LED | VR_LED | VY_LED | VG_LED);

  DDRB &= ~(SW1 | SW2 | SW3);

  //ALL LED OFF
  PORTD = 0;
}

void run(const byte LEDR, const byte LEDY, const byte LEDG, const int t){
  int ct = timer-t;
  if(ct==1){
    PORTD &= ~LEDR;
    PORTD |= LEDG;
  }
  else if(ct==8250){
    PORTD |= LEDG;
  }
  else if(ct==8500){
    PORTD &= ~LEDG;
  }
  else if(ct==8750){
    PORTD |= LEDG;
  }
  else if(ct==9000){
    PORTD &= ~LEDG;
  }
  else if(ct>9250 && ct<12500){
    PORTD |= LEDY;
  }
  else if(ct==12500){
    PORTD &= ~LEDY;
    PORTD |= LEDR;
  }
}

void flash(const byte LEDA, const byte LEDB){
  if(timer==0){
    PORTD |= LEDA;
    PORTD |= LEDB;
  }
  else if(timer==500){
    PORTD &= ~LEDA;
    PORTD &= ~LEDB;
  }
}

void loop()
{
  // 0 0 0
  if(!(PINB & SW1) && !(PINB & SW2) && !(PINB & SW3)){
    if(mode != 0){
      mode = 0;
      timer = 0;
      PORTD = 0;
    }
    mode = 0;
    if(timer==0){
      PORTD |= VR_LED;
    }
    else if(timer<=12500){
      run(HR_LED, HY_LED, HG_LED, 0);
    }
    else if(timer>12500 && timer<=25000){
      run(VR_LED, VY_LED, VG_LED, 12500);
    }
    else if(timer>25000){
      timer = 0;
    }
  }
  // 1 0 0
  else if((PINB & SW1) && !(PINB & SW2) && !(PINB & SW3)){
    if(mode != 1){
      mode = 1;
      timer = 0;
      PORTD = 0;
    }
    if(timer==1000){
      timer = 0;
    }
    flash(HR_LED, VY_LED);
  }
  // 1 1 0
  else if((PINB & SW1) && (PINB & SW2) && !(PINB & SW3)){
    if(mode != 2){
      mode = 2;
      timer = 0;
    }
    PORTD = HG_LED | VR_LED;
  }
  // 1 1 1
  else if((PINB & SW1) && (PINB & SW2) && (PINB & SW3)){
    if(mode != 3){
      mode = 3;
      timer = 0;
    }
    PORTD = VG_LED | HR_LED;
  }
  else{
    mode = -1;
    PORTD = 0;
  }
  delay(1);
  timer++;
}