Star.pde

class Star {

  //position
  float x;
  float y;
  float z;
  //previous position
  float px;
  float py;
  float pz;

  Star() {
    x=random(-width, width);
    y=random(-height, height);
    z=random(width);
    px=z;
  }

  void update() {
    z=z-speed;
    if (z < 20)
    {
      z=width; 
      x=random(-width, width);
      y=random(-height, height);
      
      pz=z;
    }
    
  }

  void show() {

    fill(255);
    noStroke();
    float sx  = map(x / z, 0, 1, 0, width/2);
    float sy  = map(y / z, 0, 1, 0, height/2);

    //float r = map(z, 0, width/2, 16, 0);
    //ellipse(sx, sy, r, r);

    float px  = map(x / pz, 0, 1, 0, width/2);
    float py  = map(y / pz, 0, 1, 0, height/2);
    pz=z;
    stroke(255);
    line(px, py, sx, sy);
  }
}