int button = 2;
int led = 13;
int ledOn=LOW;
void setup() {
  pinMode(led, OUTPUT);
  pinMode(button, INPUT_PULLUP);
}

void loop() {
  while (digitalRead(button) == LOW) {
    ledOn = !ledOn;
    if (ledOn) {
      digitalWrite(led, HIGH);
    } else {
      digitalWrite(led, LOW);
    }
    delay(200);
  }
}