#define TASK 5

byte digits[10] = { 
  0b00111111,      // 0
  0b00000110,      // 1
  0b01011011,      // 2
  0b01001111,      // 3
  0b01100110,      // 4
  0b01101101,      // 5
  0b01111101,      // 6
  0b00000111,      // 7
  0b01111111,      // 8
  0b01101111       // 9
  
};

const int digit_pins[] = {A2, A3, A4, A5};

void setup() 
{
  for (int i = 6; i <= 13; i++)
    pinMode(i, OUTPUT);

  for (int i = 0; i < 4; i++) 
  {
    pinMode(digit_pins[i], OUTPUT);
    digitalWrite(digit_pins[i], HIGH);
  }

}


void display_digit(unsigned short int pos, unsigned short int digit) 
{  
  for (int i = 6; i <= 13; i++) 
    digitalWrite(i, bitRead(digits[digit], i-6));

  digitalWrite(digit_pins[pos], LOW);
}


void clear_display() 
{
  for (int i = 6; i <= 13; i++) 
    digitalWrite(i, LOW);

  for (int i = 0; i < 4; i++) 
    digitalWrite(digit_pins[i], HIGH);
}

void loop() 
{
  #if TASK == 1
  

  for (int i = 0; i <= 9; i++) 
  {
    clear_display();

    display_digit(0, i);
    delay(1000);
  }

  clear_display();

  #endif

  #if TASK == 2
  

  for (int i = 0; i < 4; i++) 
  {
    clear_display();

    display_digit(i, 5);
    delay(20);
  }

  clear_display();

  #endif

  #if TASK == 3


  int delay_time = 500;

  while (delay_time > 20)
  {
    for (int i = 0; i < 4; i++) 
    {
      clear_display();

      display_digit(i, 5);
      delay(delay_time);
    }

    delay_time-=10;
  }
  clear_display();

  #endif 

  #if TASK == 4


  int digit = 0;
  int counter = 0;

  while (true)
  {
    for (int i = 0; i < 4; i++) 
    {
      clear_display();

      display_digit(i, digit);
      counter += 20;
      delay(20);
    }

    if (counter >= 1000) 
    {
      digit == 9 ? digit = 0 : digit++; 
      counter = 0;
    }

    clear_display();
  }

  clear_display();

  #endif 

  #if TASK == 5

  int number = 0;
  int counter = 0;

  while (number != 9999) 
  {
    int thousands = number / 1000; 
    int hundreds = (number / 100) % 10;
    int tens = (number / 10) % 10;     
    int ones = number % 10;

    int values[] = {thousands, hundreds, tens, ones};

    for (int i = 0; i < 4; i++) 
    {
      clear_display();
      display_digit(i, values[i]);

      delay(20);
    }
    
    counter += 1;
    
    if (counter >= 13)
    {
      number+=1;
      counter = 0;
    }
  }
  #endif
}