int stav = 1;
void setup() {
  Serial.begin(9600);
  pinMode(2, INPUT_PULLUP); //Stav
  pinMode(3, INPUT_PULLUP); //Input 1
  pinMode(4, INPUT_PULLUP); //Input 2
  pinMode(5, OUTPUT);       //LED
  Serial.println("Režim: " + String(stav));
}

void loop() {

  if(digitalRead(2) == LOW) {
    delay(20);
    stav++;
    if(stav > 4) {
      stav = 1;
    }
    Serial.println("Režim: " + String(stav));
    while(digitalRead(2) == LOW);
    delay(20);
  }

  while(digitalRead(2) == HIGH) {
    OR(3, 4);
    AND(3, 4);
    NAND(3, 4);
    XOR(3, 4);
  }
}

void OR(int tlacitko1, int tlacitko2) {
  if(stav == 1) {
    if(digitalRead(tlacitko1) == LOW || digitalRead(tlacitko2) == LOW) {
     digitalWrite(5, HIGH);
    }
    else {
      digitalWrite(5, LOW);
    }
  }
}

void AND(int tlacitko1, int tlacitko2) {
  if(stav == 2) {
    if(digitalRead(tlacitko1) == LOW && digitalRead(tlacitko2) == LOW) {
      digitalWrite(5, HIGH);
    }
    else {
      digitalWrite(5, LOW);
    }
  }
}

void NAND(int tlacitko1, int tlacitko2) {
  if(stav == 3) {
    if(digitalRead(tlacitko1) == LOW && digitalRead(tlacitko2) == LOW) {
      digitalWrite(5, LOW);
    }
    else {
      digitalWrite(5, HIGH);
    }
  }
}

void XOR(int tlacitko1, int tlacitko2) {
  if(stav == 4) {
    if(digitalRead(tlacitko1) == LOW || digitalRead(tlacitko2) == LOW) {
      if(digitalRead(tlacitko1) == LOW && digitalRead(tlacitko2) == LOW) {
       digitalWrite(5, LOW);
      }
      else {
        digitalWrite(5, HIGH);
      }
    }
    digitalWrite(5, LOW);
  }
}