float d = 0;
float x=200;
float y=200;

void setup(){
  size(400, 400);
  noFill();
  stroke(255,255,255);
  frameRate(30);
}

void draw(){
  background(0, 0, 0);
  ellipse(x,y,d,d);
  d=d+1;
}

void mouseReleased(){
  x = mouseX;
  y = mouseY;
  d = 0;
}