const int buttonPin = 13;
const int ledPin = 3;

bool buttonState = HIGH;
bool animationPaused = false;
unsigned long lastButtonPressTime = 0;
const unsigned long debounceDelay = 50;  // Adjust as needed

// Set initial brightness and direction
int brightness = 0;
int fadeAmount = 1;  // 10ms per increment, adjust as needed
const int maxBrightness = 255;
const int minBrightness = 0;

// Initialize timing variables
unsigned long previousMillis = 0;
const unsigned long interval = 5;  // 10ms per increment
const unsigned long exhaleDuration = 1000;  // 1 second exhale duration, adjust as needed

void setup() {
  pinMode(buttonPin, INPUT_PULLUP);
  pinMode(ledPin, OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();

  // Check if the interval has passed
  if (currentMillis - previousMillis >= interval && !animationPaused) {
    previousMillis = currentMillis;

    // Update brightness
    brightness += fadeAmount;

    // Ensure brightness stays within valid range (0 to 255)
    brightness = constrain(brightness, minBrightness, maxBrightness);

    // Apply brightness to the LED
    analogWrite(ledPin, brightness);

    // Reverse direction when brightness reaches maximum or minimum
    if (brightness == maxBrightness || brightness == minBrightness) {
      fadeAmount *= -1;
    }
  }

  // Add a pause (exhale duration) after each cycle
  if (brightness == minBrightness) {
    delay(exhaleDuration);
  }

  // Debounce button state
  if (millis() - lastButtonPressTime >= debounceDelay) {
    bool currentButtonState = digitalRead(buttonPin);

    if (buttonState == LOW && currentButtonState == HIGH) {
      buttonState = HIGH;
      animationPaused = !animationPaused;  // Pause animation on button press
    } else if (buttonState == HIGH && currentButtonState == LOW) {
      buttonState = LOW;
    }

    lastButtonPressTime = millis();
  }
}