// This example lights up 8 leds in sequence.
// The sequence direction is determined by a switch on pin 8.

#define pinSwitch 8                      // digital i/o pin with switch

int p = 0;                               // holds number of LED pin that is "on"

void setup() {  
  for (p=0; p<8; p++) {                  // set digital pins 0-7 as outputs 
    pinMode(p, OUTPUT);
    digitalWrite(p, LOW);                // and set them "off"
  }
  pinMode(pinSwitch, INPUT);             // set digital pin 8 as input
}

void loop() {
  digitalWrite(p, LOW);                  // set pin p "off"
  if (digitalRead(pinSwitch) == HIGH) {  // if status of the switch is pressed
    p--;                                 // advance p to previous pin
  } else {
    p++;                                 // advance p to next pin
  }
  p = (p+8) % 8;                         // loop p over values 0-7
  digitalWrite(p, HIGH);                 // set pin p "on"
  delay(200);                            // wait 200 millisecs
}