gradient

void setup()

{
size(500,500);
background(0);
noLoop();
}

void draw()

{
int Xbol = 50;
int Ybol = 50;

for (int i=0; i<0) ctrl=" 255;">255)
{
ctrl =255;
}

fill(ctrl);
stroke(ctrl);
rect(width/Xbol * i, height/Ybol*j , width/Xbol, height/Ybol);

}

}

}