Shape in Processing

void setup()
{

size (400,400);
background(250);
//noLoop();
}

void draw()
{
fill(250, 100);
rect(0,0,400,400);

strokeWeight(8);

int koorBirX;
int koorBirY;

koorBirX = mouseX;
koorBirY = mouseY;

beginShape();
vertex(koorBirX,koorBirY);
vertex(koorBirX+20,koorBirY);
vertex(koorBirX+20,koorBirY+20);
vertex(koorBirX+40,koorBirY+20);
vertex(koorBirX+40,koorBirY+40);
vertex(koorBirX,koorBirY+40);
endShape(CLOSE);

}