/*
  ECE 462 Object-Oriented Programming using C++ and Java
  by Yung-Hsiang Lu, Purdue University

  This program is for reference only.  It is YOUR RESPONSIBILITY
  to discover and correct mistakes, if any.  If you find a
  mistake, please inform the instructor.
*/

import java.awt.Color;
import java.awt.Graphics;
import java.awt.BorderLayout;
import java.util.Random;
import javax.swing.JApplet;
import javax.swing.JFrame;

class Main {
    public static void main(String[] args) {
        JFrame jf = new JFrame("Hello Applet");
        NewJApplet nja = new NewJApplet(360, 250);
        jf.getContentPane().add(nja, BorderLayout.CENTER);
        jf.pack();
        jf.setSize(400, 300);
        jf.setVisible(true);
    }

}

class NewJApplet extends JApplet {

    boolean inApplet = true;
    int jaWidth = 350;
    int jaHeight = 200;
    Color jaBackground = Color.YELLOW;
    double jaX, jaY;
    double jaVx, jaVy;
    int jaSize = 6;

    public NewJApplet() {
        inApplet = true;
        init();
    }

    public NewJApplet(int w, int h) {
        jaWidth = w;
        jaHeight = h;
        inApplet = false;
        init();
    }

    private void makeUnit() {
        double magnitude = Math.sqrt(jaVx * jaVx + jaVy * jaVy);
        if (magnitude > 0) {
            jaVx /= magnitude;
            jaVy /= magnitude;
        }
    }

    public void init() {

        if (inApplet) {
            jaWidth = getWidth();
            jaHeight = getHeight();
            jaBackground = Color.LIGHT_GRAY;
        } else {
            jaBackground = Color.CYAN;
        }
        setSize(jaWidth, jaHeight);
        Random ranObj = new Random();
        jaVx = ranObj.nextDouble() + 0.2;
        jaVy = ranObj.nextDouble() + 0.2;
        makeUnit();
        jaX = jaWidth / 2;
        jaY = jaHeight / 2;
    }

    public void paint(Graphics gfx) {
        gfx.setColor(jaBackground);
        gfx.fillRect(0, 0, jaWidth, jaHeight);
        gfx.setColor(Color.BLACK);
        gfx.drawString(String.valueOf(inApplet),
                jaWidth / 2, jaHeight / 2);
        jaX += jaVx;
        jaY += jaVy;

        if (jaX < jaSize) {
            jaX = jaSize;
            jaVx = -jaVx;
        }
        if (jaX > (jaWidth - jaSize)) {
            jaX = (jaWidth - jaSize);
            jaVx = -jaVx;
        }
        if (jaY < jaSize) {
            jaY = jaSize;
            jaVy = -jaVy;
        }
        if (jaY > (jaHeight - jaSize)) {
            jaY = (jaHeight - jaSize);
            jaVy = -jaVy;
        }
        gfx.setColor(Color.RED);
        gfx.fillOval((int) jaX, (int) jaY,
                jaSize, jaSize);
        try {
            Thread.sleep(10);
        } catch (InterruptedException exp) {

        }
        repaint();
    }

}