 
 void loop()
 {
-  photocell_reading = analogRead(photocell_pin);
-  
+  // PHOTOCELL
   // When it gets bright or dark, make a sound.
   // Don't play the sound again until it's normal lighting out.
+  photocell_reading = analogRead(photocell_pin);
+  
   if ( photocell_reading >= 700 && photocell_reading <= 710 )
   {
     normal_light_flag = 1;


void play_song(int song_number)
{
  int note_length = 0;
  
  // 26 notes long
  for ( int i = 0; i < 26; i++ )
  {
    if ( song_number == 0 || song_number > 0 )
    {
      note_length = 1000 / mary_had_a_little_lamb_lengths[i];
      tone(speakerPin, mary_had_a_little_lamb_notes[i], note_length);
    }
    
    int pause_between_notes = note_length * 1.30;
    delay(pause_between_notes);

    normal_light_flag = 0;
  }
  
  // BUTTON
  button_state = digitalRead(button_pin);
  
  if ( button_state == HIGH )
