byte digits[10] = {
  B00111111,
  B00000110,
  B01011011,
  B01001111,
  B01100110,
  B01101101,
  B01111101,
  B00000111,
  B01111111,
  B01101111
};

int dataPin = 11;
int latchPin = 12;
int clockPin = 9;
int button1 = 2;
int button2 = 3;
int buzzer = 5;

int counter = 0;

void displayDigit(int number) {
  byte digitPattern = digits[number];
  digitalWrite(latchPin, LOW);
  shiftOut(dataPin, clockPin, LSBFIRST, digitPattern);
  digitalWrite(latchPin, HIGH);
}

void beep() {
  tone(buzzer, 1000, 100);
}

void checkButtons() {
  if (digitalRead(button1) == LOW) {
    delay(50);
    if (digitalRead(button1) == LOW) {
      counter++;
      if (counter > 99) {
        counter = 99;
        beep();
      }
      while(digitalRead(button1) == LOW);
    }
  }
  
  if (digitalRead(button2) == LOW) {
    delay(50);
    if (digitalRead(button2) == LOW) {
      counter--;
      if (counter < 0) {
        counter = 0;
        beep();
      }
      while(digitalRead(button2) == LOW);
    }
  }
}

void setup() {
  pinMode(dataPin, OUTPUT);
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(button1, INPUT_PULLUP);
  pinMode(button2, INPUT_PULLUP);
  pinMode(buzzer, OUTPUT);
  displayDigit(0);
}

void loop() {
  checkButtons();
  displayDigit(counter);
}