/*
 *@author James McKenzie
 *@lang C89 Based
 *@contact lunarised@outlook.com
 */
int i;
void setup() {
  pinMode(10, OUTPUT);
  pinMode(11, OUTPUT);
  pinMode(12, OUTPUT);
  pinMode(13, OUTPUT);
  pinMode(0, INPUT_PULLUP);
  pinMode(1, INPUT_PULLUP);
  i = 0;
}

void loop() {
  checkOverflow(i);
  bitCheck(i);
  inCheck();
}
/*
 * Checks for button inputs on pins 0 and 1
 */
void inCheck(){
  if (digitalRead(0)==LOW){
  i++;
  delay(250);
 }
  if (digitalRead(1)==LOW){
  i--;
  delay(250);
 }
}
/*
 * Takes an int and sets leds on and off accordingly
 * @param i The current value to be displayed
 */
void bitCheck(int i){
  if (i & 1){
    digitalWrite(13, HIGH);
 }
  else{
    digitalWrite(13, LOW);
 }
  if (i & 2){
    digitalWrite(12, HIGH);
 }
  else{
    digitalWrite(12, LOW);
 }
  if (i & 4){
    digitalWrite(11, HIGH);
 }
  else{
    digitalWrite(11, LOW);
 }
  if (i & 8){
    digitalWrite(10, HIGH);
 }
 else{
    digitalWrite(10, LOW);
 }
}
/*
 * Checks to make sure the number displayed doesnt overflow
 * @param i The number to check overflow
 */
void checkOverflow(int i){
  if (i == 16){
    i = 0;
  }
  if (i == -1){
    i = 15;
  }
}