hi, like this with rectangle in the background and right opacity settings i can blur together
last frame with the next one...
the problem is i need only one zone of the sketch to do that
and i need background function to be active for another things

how to combine the two? when i turn on background function the trace fx of course dont work anymore

1. void setup(){
     size(500,500);
    
   }
   
   
   void draw(){
   
   //background(255);
   
   fill(255,255,255,20);
   noStroke();
   rect(0,0,width,height);
   fill(0);
   ellipse(mouseX, mouseY,50,50);
    
    
   }