void setup() {
	size( 510, 510 );
	smooth();

	background( 200 );
}

void draw() {
	if ( mousePressed ) {
		rects(1);
	}
	else {
		rects(0);
	}
}

void rects( int rand ) {
	int cwidth = 50;
	int cheight = 50;

	int curwidth = cwidth-(cwidth/5);
	int curheight = cheight-(cwidth/5);

	noStroke();

	for ( int y = cheight/5; y <= height; y += cheight ) {
		for ( int x = cwidth/5; x <= width; x += cwidth ) {
			if ( rand == 1 ) {
				fill( random(180,220) );
			} 
			else {
				fill( 210 );
			}

			if ( (mouseX > x) && (mouseX < x + curwidth) &&
					(mouseY > y) && (mouseY < y + curheight) ) { 

				// mouse is inside rectangle
			}
			else {
				rect( x, y, curwidth, curheight );
			}
		}
	}
}