const int ledPin = 9;
const int buttonPin = 2;

unsigned long startTime = 0;

bool ledOn = false;
bool previousButtonState = HIGH;

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

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

  bool buttonState = digitalRead(buttonPin);

  // 偵測按下按鈕的瞬間
  if (previousButtonState == HIGH && buttonState == LOW) {
    if (ledOn == false) {
      ledOn = true;
      startTime = currentMillis;
      digitalWrite(ledPin, HIGH);
    }
  }

  // LED 亮起超過 3 秒，就熄滅
  if (ledOn == true) {
    if (currentMillis - startTime >= 3000) {
      ledOn = false;
      digitalWrite(ledPin, LOW);
    }
  }

  // 記錄這一次的按鈕狀態
  previousButtonState = buttonState;
}