public static void main(String[] args) {
        StdDraw.square(.2, .8, .1);
        StdDraw.filledSquare(.8, .8, .2);
        StdDraw.circle(.8, .2, .2);

        StdDraw.setPenColor(StdDraw.BOOK_RED);
        StdDraw.setPenRadius(.02);
        StdDraw.arc(.8, .2, .1, 200, 45);

        // draw a blue diamond
        StdDraw.setPenRadius();
        StdDraw.setPenColor(StdDraw.BOOK_BLUE);
        double[] x = { .1, .2, .3, .2 };
        double[] y = { .2, .3, .2, .1 };
        StdDraw.filledPolygon(x, y);

        // text
        StdDraw.setPenColor(StdDraw.BLACK);
        StdDraw.text(0.2, 0.5, "black text");
        StdDraw.setPenColor(StdDraw.WHITE);
        StdDraw.text(0.8, 0.8, "white text");

	StdDraw.show(1000);
	StdDraw.clear();
	StdDraw.setCanvasSize(800, 800);
	StdDraw.setPenColor(StdDraw.BLACK);

	StdDraw.circle(0.95, 0.5,0.005);
	StdDraw.show(1000);
	StdDraw.circle(0.98, 0.5,0.005);
	StdDraw.show(1000);
	StdDraw.circle(1.02, 0.5,0.005);
	StdDraw.show(1000);
	StdDraw.circle(1.06, 0.5,0.005);
	StdDraw.show(1000);

	while(true) {
		if(StdDraw.mousePressed()) {
			double xx = StdDraw.mouseX();
			double yy = StdDraw.mouseY();
			System.out.println("click: (" + xx + ", " + yy + ")");
			StdDraw.circle(xx,yy,0.005);
		}
		StdDraw.show(100);
	}
    }