Simple Sketch to Randomly Choose LEDs

cointoss.ino

const int BUTTON_PIN = 9;
const int LED_PIN = 13;
const int LED2_PIN = 10;

int state = 0;
int lastVal = 0;

int ledState = LOW;
int led2State = LOW;

long startTime = 0;

void setup() {
  pinMode(LED_PIN, OUTPUT);
  pinMode(LED2_PIN, OUTPUT);
  pinMode(BUTTON_PIN, INPUT_PULLUP);
  randomSeed(analogRead(0));
}

void loop() {
  int val = digitalRead(BUTTON_PIN);
  if ((val == LOW) && (lastVal == HIGH)) {
    if (state == 0 || state == 2) {
      state = 1;
    }
    startTime = millis();
  }
  lastVal = val;

  if (state == 1 && millis() > startTime + 10000) {
    state = 2;
    long rnd = random(100);
    if (rnd < 50) {
      ledState = HIGH;
      led2State = LOW;
    } else {
      ledState = LOW;
      led2State = HIGH;
    }

    startTime = millis();
  }
  if (state == 2 && millis() > startTime + 10000) {
    state = 0;
    startTime = millis();
  }


  if (state == 0) {
    digitalWrite(LED_PIN, LOW);
    digitalWrite(LED2_PIN, LOW);

    
  } else if (state == 1) {
    digitalWrite(LED_PIN, ledState);
    digitalWrite(LED2_PIN, led2State);

    if (ledState == LOW) {
      ledState = HIGH;
      led2State = LOW;
    } else {
      ledState = LOW;
      led2State = HIGH;
    }
    delay(200);
    

  } else {
    digitalWrite(LED_PIN, ledState);
    digitalWrite(LED2_PIN, led2State);
  }
}