// demonstrates use of recursion graphically

import java.awt.*;
import javax.swing.JApplet;

public class PiledSquares extends JApplet {
	
	private static final long serialVersionUID = 1L;
	private final int APPLET_WIDTH = 320;
	private final int APPLET_HEIGHT = 320;
	private final int MIN = 20;  // smallest picture size
	private static final Color[ ] choices = new Color[ ] {Color.red, Color.blue, Color.yellow};
	
	/*
	 * sets the window size
	 */
	public void init( ) {
		setSize(APPLET_WIDTH, APPLET_HEIGHT);
	}

	/*
	 * returns next color in sequence
	 */
	public int nextColor(int index) {
		index++;
		if (index >= choices.length) {
			index = 0;
		}
		return index;
	}
	
	/*
	 * draws a rectangle, then calls itself recursively
	 */
	public void drawPictures(int size, Graphics page, int colorChoice) {
		page.setColor(choices[colorChoice]);
		page.fillRect(size/2, size/2, size/2, size/2);
		colorChoice = nextColor(colorChoice);
		page.setColor(choices[colorChoice]);
		page.fillRect(size/4, size/2 + size/4, size/4, size/4);
		page.fillRect(size/2 + size/4, size/4, size/4, size/4);
		page.fillRect(size/2 + size/4, size/2 + size/4, size/4, size/4);
		
		if (size > MIN) {
			drawPictures(size/2, page, colorChoice);
		}
	}
	
	/*
	 * perform the initial call to the drawPictures method
	 */
	public void paint (Graphics page) {
		drawPictures(APPLET_WIDTH, page, 0);
	}

}