#include <Adafruit_SSD1306.h> // OLED display library
#define OLED_RESET 10 // OLED reset pin
Adafruit_SSD1306 display(OLED_RESET); // Create display object

const int buttonPin = 10; // Button pin
int buttonState = 0; // Current button state
int lastButtonState = 0; // Last button state
unsigned long startTime = 0; // Start time for countdown
const int countdownDuration = 10; // Countdown duration in seconds

void setup() {
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C); // Initialize display
  display.clearDisplay(); // Clear display
  display.setTextColor(WHITE, BLACK); // Set text color
  display.setTextSize(1); // Set text size
  display.setCursor(0,0); // Set cursor position
  display.println("Press button"); // Display message
  display.println("to start timer"); // Display message
  display.display(); // Show message
  pinMode(buttonPin, INPUT_PULLUP); // Set button pin as input with internal pull-up resistor
}

void loop() {
  buttonState = digitalRead(buttonPin); // Read button state
  if (buttonState != lastButtonState && buttonState == LOW) { // If button state changed from HIGH to LOW
    startTime = millis(); // Record start time
    display.clearDisplay(); // Clear display
    display.setCursor(0,0); // Set cursor position
    display.println("Sequence 1"); // Display message
    display.println("Countdown:"); // Display message
    display.display(); // Show message
  }
  lastButtonState = buttonState; // Update last button state
  if (startTime > 0) { // If countdown has started
    int remainingTime = countdownDuration - (millis() - startTime) / 1000; // Calculate remaining time
    if (remainingTime >= 0) { // If countdown not over
      display.setCursor(0, 20); // Set cursor position
      display.print(remainingTime); // Display remaining time
      display.print("  "); // Display message
      display.display(); // Show message
    } else { // If countdown over
      startTime = 0; // Reset start time
      display.clearDisplay(); // Clear display
      display.setCursor(0,0); // Set cursor position
      display.println("Sequence 1"); // Display message
      display.println("Countdown done!"); // Display message
      display.display(); // Show message
    }
  }
}