This little code works with the following websites

www.sketchpatch.net   http://www.sketchpatch.net/view/9rCW0WlslS9/

sketch.processing.org

1. int k;
   boolean forward;
   void setup(){
     size(255,255);
     loadPixels();
      smooth();
   
      frameRate(3000);
     ellipseMode(CENTER);
     background(255);
     noStroke();
     //  t= new color[233];
   }
   void draw(){
   
     if (k>width-1)forward = false;
   
     if (k<1)forward = true;
   
   //  background(233,23,23);
   fill(233,23,23);
   rect(2,0,width,height-2);
     if (mouseX>45){
       fill(1);
   
       ellipse(mouseX,mouseY,35,35);
       fill(-1);
       ellipse(mouseX,mouseY,30,30);
       for (int o=0;o<k;o++){
         color a = pixels[o];
         int _x =(int) red(a);
         int _y = (int)green(a);
         fill(1);
         ellipse(_x,_y,35,35);
         // fill(-1);
         // ellipse(_x,_y,30,30);
       }
   
       for (int o=0;o<k;o++){
         color a = pixels[o];
         int _x =(int) red(a);
         int _y = (int)green(a);
         //    fill(1);
         // ellipse(_x,_y,35,35);
         fill(-1);
         //fill(_x,_y,_x,111);
         ellipse(_x,_y,30,30);
       }
   
       if (forward) k++;
       if (!forward)k--;
     }
     if (k>width-1)forward = false;
   
     if (k<2)forward = true;
     if (k>0 && k <width-1) pixels[k]=color(pmouseX,pmouseY,255);
   }
   
   
   
   

I have to try it with psjsandbox

I just tried with www.sketchpatch.cc and it works great.

You can invite persons in and chat as well as work together.