Easter Egg-F-O

#define NUMLEDS 4

void setup() {
  // put your setup code here, to run once:
  for (int i = 0; i <= NUMLEDS ; i++) {
    pinMode(i,OUTPUT);
  }
  
  setAll(LOW);
  test();
}

void loop() {
  
  for (int s = 200; s > 10 ; s = s - 10) {
    walk(s, 1);
  }

  blinkAll(100, 10);
  fill(100, 10);
  oddEven(200, 10);
}

void setAll(boolean state) {
  for (int i = 0; i <= NUMLEDS ; i++) {
    digitalWrite(i, state);
  }
}

void monoLight(int index, int delayMs) {
  setAll(LOW);
  digitalWrite(index, HIGH);
  delay(delayMs);
}

void test() {
  for (int i = 0; i <= NUMLEDS ; i++) {
    monoLight(i, 1000);
  }
}

void walk(int speed, int repeat) {
  for (int r = 0; r < repeat; r++) {
    for (int i = 0; i <= NUMLEDS ; i++) {
      monoLight(i, speed);
    }
  }
}

void blinkAll(int speed, int repeat) {
  for (int r = 0; r < repeat; r++) {
    setAll(HIGH);
    delay(speed);
    setAll(LOW);
    delay(speed);
  }
}

void fill(int speed, int repeat) {
  for (int r = 0; r < repeat; r++) {
    for (int i = 0; i <= NUMLEDS ; i++) {
      digitalWrite(i, HIGH);
      delay(speed);
    }
    for (int i = 0; i <= NUMLEDS ; i++) {
      digitalWrite(i, LOW);
      delay(speed);
    }
  }
}

void oddEven(int speed, int repeat) {
  for (int r = 0; r < repeat; r++) {
    setAll(LOW);
    for (int i = 0; i <= NUMLEDS ; i = i + 2) {
      digitalWrite(i, HIGH);
    }
    delay(speed);
    setAll(LOW);
    for (int i = 1; i <= NUMLEDS ; i = i + 2) {
      digitalWrite(i, HIGH);
    }
    delay(speed);
  }
}