Simon Says Memory Game (Arduino)

// Simon: repeat the growing light + tone sequence.
const int leds[4]  = {2, 3, 4, 5};
const int btns[4]  = {8, 9, 10, 11};
const int buzzer   = 6;
const int notes[4] = {262, 330, 392, 523};

int seq[100];
int len = 0;

void flash(int i, int ms) {
  digitalWrite(leds[i], HIGH);
  tone(buzzer, notes[i], ms);
  delay(ms);
  digitalWrite(leds[i], LOW);
  noTone(buzzer);
  delay(150);
}

int waitForPress() {
  while (true) {
    for (int i = 0; i < 4; i++) {
      if (digitalRead(btns[i]) == LOW) {
        flash(i, 200);
        while (digitalRead(btns[i]) == LOW) {}  // wait for release
        return i;
      }
    }
  }
}

void setup() {
  for (int i = 0; i < 4; i++) { pinMode(leds[i], OUTPUT); pinMode(btns[i], INPUT_PULLUP); }
  pinMode(buzzer, OUTPUT);
  randomSeed(analogRead(A0));
}

void loop() {
  seq[len++] = random(4);                       // extend the sequence
  for (int i = 0; i < len; i++) flash(seq[i], 400); // play it

  for (int i = 0; i < len; i++) {               // player repeats it
    if (waitForPress() != seq[i]) {             // wrong -> game over
      for (int j = 0; j < 3; j++) { tone(buzzer, 150, 200); delay(300); }
      len = 0; delay(1000); return;             // restart
    }
  }
  delay(800);
}