// Simple macros to remember which direction to shift LEDs
#define UP true
#define DOWN false

// Will be used to track how long since last event "fired"
unsigned long previousMillis=0;

// Delay to determine when we see the next LED
unsigned long interval = 250;

// Array with Arduino pins containing LEDs in sequence
byte LEDpins[] = {
2,3,4,5,6,7};

// Variable to track which LED to turn on, start at 000001
int LEDstate=0x01;

// State variable to know which direction to shift
boolean direction=UP;

void setup() {
	// Optional: Push Button to turn on all LEDs (to test)
	pinMode(12, INPUT_PULLUP);

	// Set Pins with LEDs to OUTPUT
	for (int x=0; x < 6; x++)
		pinMode(LEDpins[x], OUTPUT);
}

void loop() {
	// Set the pins of each LED during each iteration
	// You'll only see something change when "LEDpins" gets updated
	for (int x=0; x < 6; x++)
		digitalWrite(LEDpins[x], bitRead(LEDstate,x));

	// Test Funciton to turn on all LEDs with pushbutton
	if (digitalRead(12) == LOW)
		turnOnAll();

	// Get current time and determine how long since last check
	unsigned long currentMillis = millis();
	if ((unsigned long)(currentMillis - previousMillis) >= interval) {
		// We've waited "interval" amount of time, so let's do some stuff!

		// "Reset" our clock
		previousMillis = currentMillis;

		if (direction==UP) {
			// Use "<<" to "bit-shift" everything to the left once
			LEDstate = LEDstate << 1;
			// 0x20 is the "last" LED, another shift makes the value 0x40
			if (LEDstate == 0x40) {
				// turn on the one before "0x20" and reverse direction
				LEDstate = 0x10;
				direction = DOWN;
			}
		} else {
			// use ">>" to "bit-shift" all bits in LEDstate once to the right
			LEDstate = LEDstate >> 1;
			// This means we ran out of bits!
			if (LEDstate == 0x00) {
				// set one ahead so no extra delay
				LEDstate = 0x02;
				direction = UP;
			}
		}
	}
}

void turnOnAll() {
	// Simple code to turn on all LEDs, this "blocks"
	// so when code returns, the same LED in LEDstate will be "saved"
	while (digitalRead(12)==LOW) {
		for (int x=0; x< 6; x++)
			digitalWrite(LEDpins[x], HIGH);
	}
}