int led = 13;
int rbutton = 10;
int pbutton = 11;
int lbutton = 12;
#define LEFT LOW
#define RIGHT HIGH
#define XMAX 1400
int xposition;
int movedirection;

// Definition of the frequecies in hertz.
// http://pages.mtu.edu/~suits/notefreqs.html
#define c4 262
#define cS4 277
#define d4 294
#define dS4 311
#define e4 330
#define f4 349
#define fS4 370
#define g4 392
#define gS4 415
#define a4 440
#define aS4 466
#define b4 494
#define c5 523
#define cS5 554
#define d5 587
#define dS5 622
#define e5 659
#define f5 698
#define fS5 740
#define g5 784
#define gS5 831
#define a5 880

void setup() {                
  pinMode(led, OUTPUT); 
  pinMode(lbutton, INPUT);
  pinMode(rbutton, INPUT);
  pinMode(8, OUTPUT);  // ENABLE 
  digitalWrite(8, LOW);  
  pinMode(5, OUTPUT); // DIRECTION
  digitalWrite(5, LOW);
  pinMode(2, OUTPUT);  // PULSE
  xposition=XMAX/2;
  xposition = 0;
  Serial.begin(9600);
}

void moveHead(int dir, int n){
  int i;
  
  movedirection = dir;
  digitalWrite(5, movedirection);
  digitalWrite(led, HIGH);
  for (i=0; i<n; i++) {
    digitalWrite(2, HIGH);
    delayMicroseconds(350);
    digitalWrite(2, LOW);
    delayMicroseconds(350);  
    if (dir==RIGHT) xposition += 1;
    else xposition -= 1;
 }
  digitalWrite(led, LOW);
}

void playNote(int frequency, int duration){
  // frequency: hertz. duration: millisec
  int i;
  int length, dur;
  long x;
  #define PULSEON 350 // microsec
  #define PULSEOFF 350 // microsec
  // frequency *= 2;
  
  // calculate how much time (microsec) we have to wait between pulses:
  length = 1000000/frequency-PULSEON-PULSEOFF;
  // calculate how many pulse cycles are in duration:
  x = ((long) duration)*((long) frequency);
  x = x/((long) 1000);
  dur = x;
  if (xposition>XMAX-300) movedirection = LEFT;
  if (xposition<300) movedirection = RIGHT;
  // else keep movedirection as it was last time
  // set move direction:
  digitalWrite(5, movedirection);
  digitalWrite(led, HIGH);
  for (i=0; i<dur; i++){
    digitalWrite(2, HIGH);
    delayMicroseconds(PULSEON);
    digitalWrite(2, LOW);
    delayMicroseconds(PULSEOFF);
    delayMicroseconds(length);
    if (movedirection==RIGHT) xposition += 1;
    else xposition -= 1;
  }
}

void playImperialMarch(){
  // http://processors.wiki.ti.com/index.php/Playing_The_Imperial_March#
    playNote(a4, 500);
    playNote(a4, 500);
    playNote(a4, 500);
    playNote(f4, 350);
    playNote(c5, 150);
    playNote(a4, 500);
    playNote(f4, 350);
    playNote(c5, 150);
    playNote(a4, 650);
    delay(150);
    playNote(e5, 500);
    playNote(e5, 500);
    playNote(e5, 500);
    playNote(f5, 350);
    playNote(c5, 150);
    playNote(gS4, 500);
    playNote(f4, 350);
    playNote(c5, 150);
    playNote(a4, 650);
    delay(150);
    playNote(a5, 500);
    playNote(a4, 300);
    playNote(a4, 150);
    playNote(a5, 400);
    playNote(gS5, 200);
    playNote(g5, 200);
    playNote(fS5, 125);
    playNote(f5, 125);
    playNote(fS5, 250);
    delay(250);
    playNote(aS4, 250);
    playNote(dS5, 400);
    playNote(d5, 200);
    playNote(cS5, 200);
    playNote(c5, 125);
    playNote(b4, 125);
    playNote(c5, 250);
    delay(250);
    playNote(f4, 125);
    playNote(gS4, 500);
    playNote(f4, 375);
    playNote(a4, 125);
    playNote(c5, 500);
    playNote(a4, 375);
    playNote(c5, 125);
    playNote(e5, 650);
    delay(150);
    playNote(a5, 500);
    playNote(a4, 300);
    playNote(a4, 150);
    playNote(a5, 400);
    playNote(gS5, 200);
    playNote(g5, 200);
    playNote(fS5, 125);
    playNote(f5, 125);
    playNote(fS5, 250);
    delay(250);
    playNote(aS4, 250);
    playNote(dS5, 400);
    playNote(d5, 200);
    playNote(cS5, 200);
    playNote(c5, 125);
    playNote(b4, 125);
    playNote(c5, 250);
    delay(250);
    playNote(f4, 250);
    playNote(gS4, 500);
    playNote(f4, 375);
    playNote(c5, 125);
    playNote(a4, 500);
    playNote(f4, 375);
    playNote(c5, 125);
    playNote(e5, 650);
}

void returnHome(){
  while (xposition>0)
    moveHead(LEFT, 1);
}

void loop() {
  // https://melodyful.com/complete-list-of-music-symbols-with-their-meaning
  if (digitalRead(lbutton)==HIGH){
    while (digitalRead(lbutton)==HIGH)
      moveHead(LEFT, 1);
    xposition = 0;
  }  
  if (digitalRead(rbutton)==HIGH){
    while (digitalRead(rbutton)==HIGH)
      moveHead(RIGHT, 1);
    xposition = XMAX;
  }  
  if (digitalRead(pbutton)==HIGH){
    playImperialMarch();
   delay(5000);
   returnHome();
  }
}