int ledPin = D2;

// Our button wired to D0
int buttonPin = D3;

void setup()
{

  // For input, we define the
  // pushbutton as an input-pullup
  // this uses an internal pullup resistor
  // to manage consistent reads from the device

  pinMode( buttonPin , INPUT_PULLUP); // sets pin as input

  // We also want to use the LED

  pinMode( ledPin , OUTPUT ); // sets pin as output

}

void loop()
{
   // find out if the button is pushed
   // or not by reading from it.
   int buttonState = digitalRead( buttonPin );

  // remember that we have wired the pushbutton to
  // ground and are using a pulldown resistor
  // that means, when the button is pushed,
  // we will get a LOW signal
  // when the button is not pushed we'll get a HIGH

  // let's use that to set our LED on or off

  if( buttonState == LOW )
  {
    // turn the LED On
    digitalWrite( ledPin, HIGH);
  }else{
    // otherwise
    // turn the LED Off
    digitalWrite( ledPin, LOW);

  }


}