const byte tasterRot = 6;
const byte tasterGruen = 5;
const byte tasterBlau = 4;
const byte tasterGelb = 3;

const byte ledRot = 9;
const byte ledGruen = 13;
const byte ledBlau = 12;
const byte ledGelb = 10;

const byte piezo = 11;

const unsigned int TONE1 = 1000;
const unsigned int TONE2 = 2000;

void setup() {
  pinMode(tasterRot, INPUT_PULLUP);
  pinMode(tasterGruen, INPUT_PULLUP);
  pinMode(tasterBlau, INPUT_PULLUP);
  pinMode(tasterGelb, INPUT_PULLUP);

  pinMode(piezo, OUTPUT);

  pinMode(ledRot, OUTPUT);
  pinMode(ledGruen, OUTPUT);
  pinMode(ledBlau, OUTPUT);
  pinMode(ledGelb, OUTPUT);
}

void loop() {
  digitalWrite(ledRot,   !digitalRead(tasterRot));
  digitalWrite(ledGruen, !digitalRead(tasterGruen));
  digitalWrite(ledBlau,  !digitalRead(tasterBlau));
  digitalWrite(ledGelb,  !digitalRead(tasterGelb));

  if( !digitalRead(tasterRot))
  {
    tone(piezo, TONE1);
  }
  else if( !digitalRead(tasterGruen) || !digitalRead(tasterBlau) || !digitalRead(tasterGelb) )
  {
    tone(piezo, TONE2);
  } 
  else 
  {
    noTone(piezo);
  }
}