const int BUTTON_PIN = 12;
const int LED_PIN    = 14;

// variables will change:
int ledState = LOW;     // the current state of LED
int lastButtonState;    // the previous state of button
int currentButtonState; // the current state of button

void setup() {
  Serial.begin(9600);                // initialize serial
  pinMode(BUTTON_PIN, INPUT_PULLUP); // set arduino pin to input pull-up mode
  pinMode(LED_PIN, OUTPUT);          // set arduino pin to output mode
}


void loop(){
  lastButtonState = currentButtonState;
  currentButtonState = digitalRead(BUTTON_PIN);

  if(lastButtonState == HIGH && currentButtonState == LOW){
    ledState = !ledState;
    digitalWrite(LED_PIN,ledState);
    delay(1000);
  }
}