#define LED 13
#define BUTTON 2

int btnState = 0;
int btnLastState = 0;
int ledState = 0;

void setup(){
  pinMode(LED, OUTPUT);
  pinMode(BUTTON, INPUT);
}

void loop(){
  btnState = digitalRead(BUTTON);

  if((btnState == HIGH) && (btnLastState == LOW)){
    ledState = 1 - ledState;
  }

  btnLastState = btnState;

  if(ledState == 1){
    digitalWrite(LED, HIGH);
  }
  else{
    digitalWrite(LED, LOW);
  }

}