const int buttonPin = 8;
int oldValue = LOW; // default/idle value for pin 8 is low.

void setup() {

  Serial.begin(115200);
  Serial.println("Press the button to turn on the light.");

  // Initialize the pin for reading the button.
  pinMode(buttonPin, INPUT);
  pinMode(LED_BUILTIN, OUTPUT);  // Set LED pin as output

}

void loop() {
  // Read the value of pin 8.
  int newValue = digitalRead(buttonPin);

  // Check if the value was changed,
  // by comparing it with the previous value.
  if(newValue != oldValue)
  {
    if(newValue == HIGH)
    {
      //Serial.println("Light on.");
      digitalWrite(LED_BUILTIN, HIGH);   // turn the LED on (HIGH is the voltage level)
    }
    else
    {
      //Serial.println("Light off.");
      digitalWrite(LED_BUILTIN, LOW);    // turn the LED off by making the voltage LOW
    }
    // Remember the value for the next time.
    oldValue = newValue;

}
 // Slow down the sketch.
  // Also for debouncing the button.
  delay(100);
}