const uint8_t PIN_LED    = 12;
const uint8_t PIN_BUTTON =  8;

// IDEE Zustand der LED im Porgramm errechnen und extern sichtbar machen
int led_status = LOW;

void setup() {
  // put your setup code here, to run once:
  pinMode(PIN_LED   , OUTPUT);
  pinMode(PIN_BUTTON, INPUT_PULLUP);
  digitalWrite(PIN_LED,led_status);
}

void loop() {
  // dedektiere abfallende Flanke (Taster über Pullup-Widerstand angeschlossen)
  while( digitalRead(PIN_BUTTON)==HIGH ) {
    // nichts
  }

  if ( led_status == LOW ) {
    led_status = HIGH;
  } else { // led_status == HIGH
    led_status =  LOW;
  }
  // LED-Status sichtbar machen
  digitalWrite(PIN_LED,led_status);

  // dedektiere asteigende Flanke (Taster über Pullup-Widerstand angeschlossen)
  while( digitalRead(PIN_BUTTON)==LOW ) {
    // nichts
  }
}