void draw() {
      background(0x00000000,10);  //slow disappear(s) with
      //image( a, 0, 0 );
      dragSegment(0, mouseX - 8, mouseY - 8);
      for(int i=0; i < x.length-1; i++) {
        dragSegment(i+1, x[i], y[i]);
      }
    }