int latchPin = 12; // pin connected ST_CP of 74HC595
int clockPin = 13; // pin connected SH_CP of 74HC595
int dataPin = 11; // pin connected DS of 74HC595


void setup() {
  // put your setup code here, to run once:
  // set pins output
  pinMode(latchPin, OUTPUT);
  pinMode(clockPin, OUTPUT);
  pinMode(dataPin, OUTPUT);
}

void loop() {
  // put your main code here, to run repeatedly:
  // define one-byte variable to use 8 bits to represent state of 8 LEDs of bar graph
  // assigned to 0x01, binary 00000001, indicate one LED light is on
  byte x = 0x01;
  for(int j = 0; j < 8; j++){
    // Output lowlevel to latch pin
    digitalWrite(latchPin, LOW);
    // send serial data to 74HC595
    shiftOut(dataPin, clockPin, LSBFIRST, x);
    // Output high level to latch pin, 74HC595 will update data to parallel output pin
    digitalWrite(latchPin, HIGH);
    
    // make variable move one bit to the left once, bright LED move one step to the left
    x <<= 1;
    delay(100); // delay 100 ms
  }
}