Push Button with Debounce

/* A digital push button switch
Push button toggle switch code with debounce time for Lilypad

Takes a push button switch as input in an LED in a circuit.
Each press of the button toggles the LED state ON or OFF.

Debounce code ignores mechanical noise in the switch producing a
clean ON or OFF state.

Written by Orwell Kowalyshyn for theMakery.space
Portions of code from Arduino.cc
*/

const int buttonPin = 5;          //define the push button and LED pin ports as constants
const int ledPin = 6;

int reading;                      //variable for switch state - open is HIGH, closed is LOW
int state = HIGH;                 //pin is turned on to start
int debounce = 300;               //200 millisecond debounce time
long timing = 0;                  //set program running time to 0, 32-bit size

void setup() {

  pinMode(buttonPin,INPUT_PULLUP);  //enable input pullup resistor on pin, default to high impedence state
  pinMode(ledPin, OUTPUT);          //set output for LED

  digitalWrite(ledPin,state);       //turn LED on by default
}

void loop() {

  reading = digitalRead(buttonPin);   //get state of the button, HIGH (open) or LOW (closed)

  if (reading == LOW && state == LOW && (millis()-timing > debounce)) {         //button action close, and LED is off, and > debounce time
    state = HIGH;                                                               //turn on LED
    timing = millis();                                                          //mark time when state changed
  }

  else if (reading == LOW && state == HIGH && (millis()-timing > debounce)) {    //button closed and LED is on, and > debounce time
    state = LOW;                                                                 //turn off LED
    timing = millis();                                                           //mark time when state change
  }

  digitalWrite(ledPin,state);         //set LED state

}