const int ledPin = 2;      
const int buttonPin = 21;   

int state = 1;              
int buttonState;            
int lastButtonState = LOW;  
unsigned long lastDebounceTime = 0;
unsigned long debounceDelay = 50;

int blinkCount = 0;         
bool ledOn = false;         
unsigned long lastBlinkTime = 0;
unsigned long blinkInterval = 1000; 
unsigned long fastBlinkInterval = 250; 

void setup() {
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT_PULLUP); 
  digitalWrite(ledPin, LOW);
  Serial.begin(115200);
}

void loop() {
  int reading = digitalRead(buttonPin);

  if (reading != lastButtonState) {
    lastDebounceTime = millis();
  }
  if ((millis() - lastDebounceTime) > debounceDelay) {
    if (reading != buttonState) {
      buttonState = reading;
      if (buttonState == LOW) {
        state++;
        if (state > 3) state = 1;
        resetBlinkState();
      }
    }
  }
  lastButtonState = reading;

  switch (state) {
    case 1:
      fixedFrequencyBlink(1000);
      break;
    case 2:
      fastBlinkSequence();
      break;
    case 3:
      digitalWrite(ledPin, LOW);
      break;
  }
}

void resetBlinkState() {
  blinkCount = 0;
  ledOn = false;
  lastBlinkTime = 0;
}

void fixedFrequencyBlink(unsigned long interval) {
  if (millis() - lastBlinkTime >= interval) {
    lastBlinkTime = millis();
    ledOn = !ledOn;
    digitalWrite(ledPin, ledOn);
  }
}

void fastBlinkSequence() {
  if (blinkCount < 5) {
    if (millis() - lastBlinkTime >= fastBlinkInterval) {
      lastBlinkTime = millis();
      ledOn = !ledOn;
      digitalWrite(ledPin, ledOn);
      if (!ledOn) blinkCount++;
    }
  } else {
    state = 1;
  }
}