int segment_a = 2;
int segment_b = 3;
int segment_c = 4;
int segment_d = 5;
int segment_e = 6;
int segment_f = 7;
int segment_g = 8;

void setup() {
  pinMode(segment_a, OUTPUT);
  pinMode(segment_b, OUTPUT);
  pinMode(segment_c, OUTPUT);
  pinMode(segment_d, OUTPUT);
  pinMode(segment_e, OUTPUT);
  pinMode(segment_f, OUTPUT);
  pinMode(segment_g, OUTPUT);
}

void loop() {
  for (int i = 0; i <= 9; i++) {
    displayDigit(i);
    delay(1000); 
  }

  for (int i = 9; i >= 0; i--) {
    displayDigit(i);
    delay(1000);
  }
}

void displayDigit(int num) {
  digitalWrite(segment_a, LOW);
  digitalWrite(segment_b, LOW);
  digitalWrite(segment_c, LOW);
  digitalWrite(segment_d, LOW);
  digitalWrite(segment_e, LOW);
  digitalWrite(segment_f, LOW);
  digitalWrite(segment_g, LOW);

  switch (num) {
    case 0:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_e, HIGH);
      digitalWrite(segment_f, HIGH);
      break;
    case 1:
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      break;
    case 2:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_e, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    case 3:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    case 4:
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_f, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    case 5:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_f, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    case 6:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_e, HIGH);
      digitalWrite(segment_f, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    case 7:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      break;
    case 8:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_e, HIGH);
      digitalWrite(segment_f, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    case 9:
      digitalWrite(segment_a, HIGH);
      digitalWrite(segment_b, HIGH);
      digitalWrite(segment_c, HIGH);
      digitalWrite(segment_d, HIGH);
      digitalWrite(segment_f, HIGH);
      digitalWrite(segment_g, HIGH);
      break;
    default:
      
      break;
  }
}