// Forum: https://forum.arduino.cc/t/algorithm-using-serial-communication/1187592
// This Wokwi project: https://wokwi.com/projects/381016354608842753

int timer = 300;
int i;
byte led1 = 8;
byte led2 = 9;
byte led3 = 10;
byte led4 = 11;
byte led5 = 12;
byte led6 = 13;
int flag = 0;
const byte st = A5;

void setup() {
  Serial.begin(9600);
  randomSeed(analogRead(0));  // para generar una nueva semilla
  pinMode(led1, OUTPUT);
  pinMode(led2, OUTPUT);
  pinMode(led3, OUTPUT);
  pinMode(led4, OUTPUT);
  pinMode(led5, OUTPUT);
  pinMode(led6, OUTPUT);
  pinMode(st, INPUT);
}

void loop() {
  if (digitalRead(st) == 1) {
    flag = !flag;
  }
  if (flag == 1) {
    if (Serial.available()) {
      char data = Serial.read();

      if (data == 'a') {
        for (i = 8; i <= 13; i++) {
          digitalWrite(i, HIGH);
          delay(900);
        }

        for (i = 8; i <= 13; i++) {
          digitalWrite(i, LOW);
          delay(900);
        }
      }

      if (data == 'b') {
        for (i = 13; i >= 8; i--) {
          digitalWrite(i, HIGH);
          delay(900);
        }

        for (i = 13; i >= 8; i--) {
          digitalWrite(i, LOW);
          delay(900);
        }
      }

      if (data == 'c') {
        int rnd = random(14); // ponemos hasta 14 ya que nunca se llega a 14
        digitalWrite(rnd, HIGH);
        delay(timer);
        digitalWrite(rnd, LOW);
        delay(timer);
      }
    }
  }
  else {
    digitalWrite(8, LOW);
    digitalWrite(9, LOW);
    digitalWrite(10, LOW);
    digitalWrite(11, LOW);
    digitalWrite(12, LOW);
    digitalWrite(13, LOW);
  }
}