#include <TimerOne.h>

// Pinout
const int digitPins[] = {2, 3, 4, 5};  // Arduino pins connected to 7-segment display digit pins
const int segmentPins[] = {6, 7, 8, 9, 10, 11, 12, 13};  // Arduino pins connected to 7-segment display segment pins
const int buttonPin = A0;  // Arduino pin connected to the push button

// Timer settings
const int timerDuration = 60;  // Countdown duration in seconds

// Global variables
int remainingTime = 0;
bool timerRunning = false;

void setup() {
  // Initialize pins
  for (int i = 0; i < 4; i++) {
    pinMode(digitPins[i], OUTPUT);
  }
  for (int i = 0; i < 8; i++) {
    pinMode(segmentPins[i], OUTPUT);
  }
  pinMode(buttonPin, INPUT_PULLUP);

  // Set initial time
  remainingTime = timerDuration;

  // Configure Timer1 interrupt
  Timer1.initialize(1000000);  // Set timer interval to 1 second
  Timer1.attachInterrupt(timerInterrupt);
}

void loop() {
  // Check if the button is pressed
  if (digitalRead(buttonPin) == LOW) {
    if (!timerRunning) {
      startTimer();
    } else {
      stopTimer();
    }
    delay(200); // Debounce delay
  }
}

void startTimer() {
  timerRunning = true;
}

void stopTimer() {
  timerRunning = false;
}

void timerInterrupt() {
  if (timerRunning) {
    remainingTime--;
    if (remainingTime <= 0) {
      stopTimer();
    }
  }
  updateDisplay();
}

void updateDisplay() {
  int minutes = remainingTime / 60;
  int seconds = remainingTime % 60;

  // Display minutes
  displayDigit(0, minutes / 10);
  displayDigit(1, minutes % 10);

  // Display seconds
  displayDigit(2, seconds / 10);
  displayDigit(3, seconds % 10);
}

void displayDigit(int digit, int value) {
  // Clear all digits
  for (int i = 0; i < 4; i++) {
    digitalWrite(digitPins[i], HIGH);
  }

  // Set the selected digit
  digitalWrite(digitPins[digit], LOW);

  // Set the segments to display the value
  switch (value) {
    case 0:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], LOW);
      digitalWrite(segmentPins[5], LOW);
      digitalWrite(segmentPins[6], HIGH);
      break;
    case 1:
      digitalWrite(segmentPins[0], HIGH);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], HIGH);
      digitalWrite(segmentPins[4], HIGH);
      digitalWrite(segmentPins[5], HIGH);
      digitalWrite(segmentPins[6], HIGH);
      break;
    case 2:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], HIGH);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], LOW);
      digitalWrite(segmentPins[5], HIGH);
      digitalWrite(segmentPins[6], LOW);
      break;
    case 3:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], HIGH);
      digitalWrite(segmentPins[5], HIGH);
      digitalWrite(segmentPins[6], LOW);
      break;
    case 4:
      digitalWrite(segmentPins[0], HIGH);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], HIGH);
      digitalWrite(segmentPins[4], HIGH);
      digitalWrite(segmentPins[5], LOW);
      digitalWrite(segmentPins[6], LOW);
      break;
    case 5:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], HIGH);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], HIGH);
      digitalWrite(segmentPins[5], LOW);
      digitalWrite(segmentPins[6], LOW);
      break;
    case 6:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], HIGH);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], LOW);
      digitalWrite(segmentPins[5], LOW);
      digitalWrite(segmentPins[6], LOW);
      break;
    case 7:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], HIGH);
      digitalWrite(segmentPins[4], HIGH);
      digitalWrite(segmentPins[5], HIGH);
      digitalWrite(segmentPins[6], HIGH);
      break;
    case 8:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], LOW);
      digitalWrite(segmentPins[5], LOW);
      digitalWrite(segmentPins[6], LOW);
      break;
    case 9:
      digitalWrite(segmentPins[0], LOW);
      digitalWrite(segmentPins[1], LOW);
      digitalWrite(segmentPins[2], LOW);
      digitalWrite(segmentPins[3], LOW);
      digitalWrite(segmentPins[4], HIGH);
      digitalWrite(segmentPins[5], LOW);
      digitalWrite(segmentPins[6], LOW);
      break;
  }
}