Vec2D v,dir;
float direction,speed;
float oldTime,newTime,diffTime;
Vec2D v2[],D;
int num=50;
float dist;

void setup() {
  size(400,400);
  //background(0,0,120);
  v=new Vec2D(160,50);
  dir=new Vec2D();
  
  direction=radians(0);
  speed=2;

  ellipseMode(CENTER_DIAMETER);
  
  oldTime=0;
  newTime=0;
  
  // neu _ mit mouse zeichnen
  v2=new Vec2D[num];
  for(int i=0; i<num; i++) v2[i]=new Vec2D();
  D=new Vec2D();

}

void loop() {

  background(0,0,120);
  newTime=millis();
  diffTime=newTime-oldTime;
  
  direction+=radians(diffTime/3000);
  
  speed=dist/100;  //mouse bewegung !!


  dir.set(speed,0);
  dir.rotate(direction);
  v.add(dir);
  if(v.x<0) v.x=width;
  else if(v.x>width) v.x=0;
  if(v.y<0) v.y=height;
  else if(v.y>height) v.y=0;
  
  noFill();
  stroke(255);
  ellipse(v.x,v.y, diffTime/40,diffTime/40);
  if(diffTime/40>100) oldTime=newTime; 
  
  
  // neu _ mit mouse zeichnen
    
    // punte/vektoren liste updaten
  for(int i=num-1; i>0; i--) v2[i].set(v2[i-1]);
  v2[0].set(mouseX,mouseY);


  // linie zwischen "leeren" punkten ziehen
  //fill(255,0,0);
  noStroke();
  for(int i=0; i<num-1; i++) line(v2[i].x,v2[i].y, v2[i+1].x,v2[i+1].y);

  // abstand aller punkte --> dist !!
  dist=0;
  for(int i=0; i<num-1; i++) {
  D.set(v2[i+1]);
  D.sub(v2[i]);
  dist+=D.length();
  }

}


void mousePressed() {
  oldTime=newTime;
}






// General vector class for 2D vectors
class Vec2D {
  float x,y;

// Constructor with no parameters
  Vec2D() {
    x=0;
    y=0;
  }
  
  Vec2D(float _x,float _y) {
    x=_x;
    y=_y;
  }

  Vec2D(Vec2D v) {
    x=v.x;
    y=v.y;
  }

  void set(float _x,float _y) {
    x=_x;
    y=_y;
  }

  void set(Vec2D v) {
    x=v.x;
    y=v.y;
  }

  void add(float _x,float _y) {
    x+=_x;
    y+=_y;
  }

  void add(Vec2D v) {
    x+=v.x;
    y+=v.y;
  }

  void sub(float _x,float _y) {
    x-=_x;
    y-=_y;
  }

  void sub(Vec2D v) {
    x-=v.x;
    y-=v.y;
  }

  void mult(float m) {
    x*=m;
    y*=m;
  }

  void div(float m) {
    x/=m;
    y/=m;
  }

  float length() {
    return sqrt(x*x+y*y);
  }

  float angle() {
    return atan2(y,x);
  }

  void normalise() {
    float l=length();
    if(l!=0) {
      x/=l;
      y/=l;
    }
  }

  Vec2D tangent() {
    return new Vec2D(-y,x);
  }

  void rotate(float val) {
    // Due to float not being precise enough, double is used for the calculations
    double cosval=Math.cos(val);
    double sinval=Math.sin(val);
    double tmpx=x*cosval - y*sinval;
    double tmpy=x*sinval + y*cosval;

    x=(float)tmpx;
    y=(float)tmpy;
  }
}