#define clockPin 10 // Clock pin of 74HC595 is connected to Digital pin 10
#define dataPin  9  // Data  pin of 74HC595 is connected to Digital pin 9 
#define latchPin 8  // Latch pin of 74HC595 is connected to Digital pin 8

int numOfRegisters = 2;
byte* registerState;

long effectId = 0;
long prevEffect = 0;
long effectRepeat = 0;
long effectSpeed = 300; // Delay in milliseconds between LED changes

int currentLED = 0; // Keeps track of the currently lit LED
boolean allLedsOn = false;

void setup() {
  // Initialize array
  registerState = new byte[numOfRegisters];
  for (size_t i = 0; i < numOfRegisters; i++) {
    registerState[i] = 0;
  }

  // Set pins to output so you can control the shift register
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);

  // Initialize Serial communication
  Serial.begin(9600);
}

void loop() {
  if (!allLedsOn) {
    // Turn off all LEDs
    for (int i = 0; i < 16; i++) {
      bitClear(registerState[i / 8], i % 8);
    }
    updateShiftRegister();
    delay(effectSpeed); // Delay for effectSpeed milliseconds

    // Turn on the current LED
    bitSet(registerState[currentLED / 8], currentLED % 8);
    updateShiftRegister();
    delay(effectSpeed); // Delay for effectSpeed milliseconds

    // Move to the next LED
    currentLED++;

    // If we've reached LED 16, reset to LED 1
    if (currentLED >= 16) {
      currentLED = 0;
      allLedsOn = true; // Set the flag to indicate all LEDs should be on next
    }
  } else {
    // Turn on all LEDs
    for (int i = 0; i < 16; i++) {
      bitSet(registerState[i / 8], i % 8);
    }
    updateShiftRegister();
    delay(effectSpeed); // Delay for effectSpeed milliseconds

    allLedsOn = false; // Set the flag to go back to counting LEDs
  }
}

void updateShiftRegister() {
  // Send the data to the shift register
  digitalWrite(latchPin, LOW);
  for (int i = numOfRegisters - 1; i >= 0; i--) {
    shiftOut(dataPin, clockPin, MSBFIRST, registerState[i]);
  }
  digitalWrite(latchPin, HIGH);
}