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

public class Light extends JPanel{

    private int state;

    public Light(){
	state = 0; // red
	setPreferredSize(new Dimension(40,120));
    }

    public void paintComponent(Graphics page){
	super.paintComponent(page);
	page.setColor(Color.black);
	page.fillRect(0,0,40,120);

        Color darkGreen = new Color (0,63,0);
	Color darkRed = new Color (63,0,0);
	Color darkYellow = new Color (63,63,0);
	Color top, middle, bottom;

	if (state == 0){ // red
	    top = Color.red;
	    middle = darkYellow;
	    bottom = darkGreen;
	}
	else if (state == 1){ // green
	    top = darkRed;
	    middle = darkYellow;
	    bottom = Color.green;
	}
	else{ // state is 2, yellow
	    top = darkRed;
	    middle = Color.yellow;
	    bottom = darkGreen;
	}

	// draw top light
	page.setColor (top);
	page.fillOval(5,5,30,30);

	// middle light
	page.setColor (middle);
	page.fillOval(5,45,30,30);

	// bottom light
	page.setColor (bottom);
	page.fillOval(5,85,30,30);
    }

    public void changeLight(){
	state = (state+1)%3;
	repaint();
    }
}