// Define pins for 7 segment display
const int SEGMENT_PINS[4][7] = {
  {2, 3, 4, 5, 6, 7, 8}, // digit 1
  {2, 3, 4, 5, 6, 7, 8}, // digit 2
  {2, 3, 4, 5, 6, 7, 8}, // digit 3
  {2, 3, 4, 5, 6, 7, 8}  // digit 4
};

// Define pins for digits
const int DIGIT_PINS[4] = {9, 10, 11, 12};

// Define pins for buttons
const int START_STOP_PIN = 13;
const int RESET_PIN = 1;

// Define variables to store time
int minutes = 0;
int seconds = 0;
int tenths = 0;

// Define variables to store button states
int startStopButtonState = LOW;
int resetButtonState = LOW;

// Define variables to store whether timer is running and whether it has been reset
bool isRunning = false;
bool isReset = true;

void setup() {
  // Set segment and digit pins as output
  for (int i = 0; i < 4; i++) {
    for (int j = 0; j < 7; j++) {
      pinMode(SEGMENT_PINS[i][j], OUTPUT);
    }
    pinMode(DIGIT_PINS[i], OUTPUT);
  }
  
  // Set button pins as input
  pinMode(START_STOP_PIN, INPUT_PULLUP);
  pinMode(RESET_PIN, INPUT_PULLUP);
  
  // Start serial communication
  Serial.begin(9600);
}

void loop() {
  // Read button states
  startStopButtonState = digitalRead(START_STOP_PIN);
  resetButtonState = digitalRead(RESET_PIN);
  
  // If reset button is pressed, reset the timer
  if (resetButtonState == LOW && !isReset) {
    isRunning = false;
    isReset = true;
    minutes = 0;
    seconds = 0;
    tenths = 0;
  }
  
  // If start/stop button is pressed, start or stop the timer
  if (startStopButtonState == LOW) {
    isRunning = !isRunning;
    delay(100);
  }
  
  // If the timer is running, increment time
  if (isRunning) {
    tenths++;
    if (tenths == 10) {
      tenths = 0;
      seconds++;
    }
    if (seconds == 60) {
      seconds = 0;
      minutes++;
    }
    if (minutes == 10) {
      minutes = 0;
    }
  }
  
  // Display time
  displayDigit(0, minutes);
  delay(2);
  displayDigit(1, seconds / 10);
  delay(2);
  displayDigit(2, seconds % 10);
  delay(2);
  displayDigit(3, tenths);
  delay(2);
}

// Display a digit on a 7 segment display
void displayDigit(int digit, int value) {
  // Define which segments to turn on for each digit
  const bool digitSegments[10][7] = {
    {1, 1, 1, 1, 1, 1, 0}, // 0
    {0, 1, 1, 0, 0, 0, 0}, // 1
    {1, 1, 0, 1, 1, 0, 1}, // 2
    {1, 1, 1, 1, 0, 0, 1}, // 3
    {0, 1, 1, 0, 0, 1, 1}, // 4
    {1, 0, 1, 1, 0, 1, 1}, // 5
    {1, 0, 1, 1, 1, 1, 1}, // 6
    {1, 1, 1, 0, 0, 0, 0}, // 7
    {1, 1, 1, 1, 1, 1, 1}, // 8
    {1, 1, 1, 1, 0, 1, 1}, // 9
  };
  
  // Turn on the necessary segments for the given value
  for (int i = 0; i < 7; i++) {
    digitalWrite(SEGMENT_PINS[digit][i], digitSegments[value][i]);
  }
  
  // Turn on the appropriate digit
  for (int i = 0; i < 4; i++) {
    digitalWrite(DIGIT_PINS[i], i == digit ? LOW : HIGH);
  }
}