import java.awt.Color;
import java.awt.Graphics;

import javax.swing.JFrame;
import javax.swing.JPanel;

public class Langton extends JFrame{
	private JPanel planePanel;
	private static final int ZOOM = 4;
	
	public Langton(final boolean[][] plane){
		planePanel = new JPanel(){
			@Override
			public void paint(Graphics g) {
				for(int y = 0; y < plane.length;y++){
					for(int x = 0; x < plane[0].length;x++){
						g.setColor(plane[y][x] ? Color.BLACK : Color.WHITE);
						g.fillRect(x * ZOOM, y * ZOOM, ZOOM, ZOOM);
					}
				}
				//mark the starting point
				g.setColor(Color.GREEN);
				g.fillRect(plane[0].length / 2 * ZOOM,
				           plane.length / 2 * ZOOM, ZOOM/2, ZOOM/2);
			}
		};
		planePanel.setSize(plane[0].length - 1, plane.length - 1);
		add(planePanel);
		setSize(ZOOM * plane[0].length, ZOOM * plane.length + 30);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setVisible(true);
	}
	
	public static void main(String[] args){
		new Langton(runAnt(100, 100));
	}

	private static boolean[][] runAnt(int height, int width){
		boolean[][] plane = new boolean[height][width];
		int antX = width/2, antY = height/2;//start in the middle-ish
		int xChange = 0, yChange = -1; //start moving up
		while(antX < width && antY < height && antX >= 0 && antY >= 0){
			if(plane[antY][antX]){
				//turn left
				if(xChange == 0){ //if moving up or down
					xChange = yChange;
					yChange = 0;
				}else{ //if moving left or right
					yChange = -xChange;
					xChange = 0;
				}
			}else{
				//turn right
				if(xChange == 0){ //if moving up or down
					xChange = -yChange;
					yChange = 0;
				}else{ //if moving left or right
					yChange = xChange;
					xChange = 0;
				}
			}
			plane[antY][antX] = !plane[antY][antX];
			antX += xChange;
			antY += yChange;
		}
		return plane;
	}
}