/*
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU Affero General Public License as
    published by the Free Software Foundation, either version 3 of
    the License, or (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Affero General Public License for more details.

    You should have received a copy of the GNU Affero General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

// pin 13 controls the arduino's built-in LED
int led_pin = 13;
// connect the button to pin 2
int button_pin = 2;
// initially, the button is not pressed.
//  0 means not pressed, 1 means pressed
int button_value = 0;

void setup(){
  Serial.begin(9600);}

void loop(){
  // see if you can figure out how this logic works
  if(digitalRead(button_pin) != button_value){
    Serial.println("button state changed!");}
  // read the value of the button pin during this loop,
  //  and save it in a box named "button_value"
  button_value = digitalRead(button_pin);
  // write the value to the led pin
  digitalWrite(led_pin, button_value);}