============
Using LibGDX
============


This page shows you how you can create a Java* game using Multi-OS Engine and the libGDX library.

Contents:
    `Set Up Your Environment`_

    `Develop Your App`_

    `Debug Your App`_

    `Summary and Resources`_

The screen shots below show the game running on an Android* device and an Apple iOS* device. On both operating systems, the game looks and behaves the same way. How is this achieved?

If you are not yet familiar with libGDX, this tutorial will help you start from scratch. So let's begin. Scroll down!

.. image:: images/libgdx1.png

.. image:: images/libgdx2.png


Set Up Your Environment
=======================

First, install these applications:

•   Git
•   Android Studio
•   Multi-OS Engine, a plugin for Android Studio

You need to add Git to your system path.

Generating a new project
================

Download the newest release of [gdx-liftoff](https://github.com/tommyettinger/gdx-liftoff).
Run the jar and configure the project. Make sure to select "iOS Multi-OS Engine" as backend, not iOS!

.. image:: images/libgdx3.png

Develop Your App
================

Open the generated project in Android Studio.

.. image:: images/libgdx4.png

So, we imported our project! Now let’s develop the common part for our application.

Core Code Part
================

First of all, create in the Core part a class called Assets for loading resources.

::

	package org.moe.libgdxmissilecommand;
	import com.badlogic.gdx.Gdx;
	import com.badlogic.gdx.audio.Sound;
	import com.badlogic.gdx.files.FileHandle;
	import com.badlogic.gdx.graphics.Texture;
	import com.badlogic.gdx.graphics.g2d.Animation;
	import com.badlogic.gdx.graphics.g2d.TextureRegion;
	public class Assets {
    	public static final float screenWidth = 800;
    	public static final float screenHeight = 480;
    	// Backgrounds
    	public static TextureRegion backgroundRegionMenu;
    	public static TextureRegion backgroundLoadGame1TextureRegion;
    	public static TextureRegion backgroundLoadGame2TextureRegion;
    	public static TextureRegion[] levelsBackgroundsTextureRegions = new TextureRegion[4];
    	// Buttons
    	public static TextureRegion backButtonTextureRegion;
    	public static TextureRegion pauseButtonTextureRegion;
    	public static TextureRegion startButtonTextureRegion;
    	public static TextureRegion creditsButtonTextureRegion;
    	// Player
    	public static TextureRegion playerBaseTextureRegion;
    	public static TextureRegion playerGunTextureRegion;
    	// Missiles
    	public static TextureRegion missileTextureRegion;
    	public static Sound missileSound;
    	// Explosions
    	public static Animation<TextureRegion> explosionAnimation;
    	public static Sound explosionSound;
    	// Cities
    	public static Animation<TextureRegion> citiesDestroyAnimation;
    	public static TextureRegion[] citiesTextureRegions = new TextureRegion[6];
    	// Naves
    	public static TextureRegion navesTextureRegion;
    	// Font file
    	public static FileHandle fontFile;
    	public static Sound alarmSound;
    	private static Texture loadTexture (String file) {
        	return new Texture(Gdx.files.internal(file));
    	}
    	public static void load() {
        	Texture backgroundMenuTexture = loadTexture("Splash2.png");
        	backgroundRegionMenu = new TextureRegion(backgroundMenuTexture, 0, 0, 800, 480);
        	Texture backgroundLoadGame1Texture = loadTexture("aviso1.png");
        	backgroundLoadGame1TextureRegion = new TextureRegion(backgroundLoadGame1Texture, 0, 0, 800, 480);
        	Texture backgroundLoadGame2Texture = loadTexture("aviso2.png");
        	backgroundLoadGame2TextureRegion = new TextureRegion(backgroundLoadGame2Texture, 0, 0, 800, 480);
        	for (int i = 0; i < levelsBackgroundsTextureRegions.length; i++) {
            	Texture backgroundLevelTexture = loadTexture("bg" + String.valueOf(i + 1) + ".png");
            	levelsBackgroundsTextureRegions[i] = new TextureRegion(backgroundLevelTexture, 0, 0, 800, 480);
        	}
        	Texture startButtonTexture = loadTexture("btStart.png");
        	startButtonTextureRegion = new TextureRegion(startButtonTexture, 0, 0, 120, 43);
        	Texture creditsButtonTexture = loadTexture("btCredits.png");
        	creditsButtonTextureRegion = new TextureRegion(creditsButtonTexture, 0, 0, 144, 43);
        	Texture backButtonTexture = loadTexture("btBack.png");
        	backButtonTextureRegion = new TextureRegion(backButtonTexture, 0, 0, 106, 43);
        	Texture pauseButtonTexture = loadTexture("btPause.png");
        	pauseButtonTextureRegion = new TextureRegion(pauseButtonTexture, 0, 0, 81, 22);
        	Texture playerBaseTexture = loadTexture("canhaopart1.png");
        	playerBaseTextureRegion = new TextureRegion(playerBaseTexture, 0, 0, 75, 45);
        	Texture playerGunTexture = loadTexture("canhaopart2.png");
        	playerGunTextureRegion = new TextureRegion(playerGunTexture, 0, 0, 8, 45);
        	Texture missileTexture = loadTexture("missil.png");
        	missileTextureRegion = new TextureRegion(missileTexture, 0, 0, 5, 9);
        	for (int i = 0; i < citiesTextureRegions.length; i++) {
            	Texture cityTexture = loadTexture("city" + String.valueOf(i + 1) + ".png");
            	citiesTextureRegions[i] = new TextureRegion(cityTexture, 0, 0, 80, 80);
        	}
        	Texture citiesDestroy = loadTexture("cidade.png");
        	citiesDestroyAnimation = new Animation(0.2f, new TextureRegion(citiesDestroy,2,53,51,59),
                	new TextureRegion(citiesDestroy,55,2,51,15));
            fontFile = Gdx.files.classpath("com/badlogic/gdx/utils/lsans-15.fnt");
        	alarmSound = Gdx.audio.newSound(Gdx.files.internal("alarm.mp3"));
        	missileSound = Gdx.audio.newSound(Gdx.files.internal("missil.mp3"));
        	Texture explosion = loadTexture("explosao1.png");
        	explosionAnimation = new Animation(0.2f, new TextureRegion(explosion,8,8,26,22),
                	new TextureRegion(explosion,35,8,40,38), new TextureRegion(explosion,76,8,60,56),
                	new TextureRegion(explosion,137,8,74,76), new TextureRegion(explosion,8,85,74,68),
                	new TextureRegion(explosion,83,85,72,68), new TextureRegion(explosion,156,85,68,62),
                	new TextureRegion(explosion,8,154,62,60), new TextureRegion(explosion,71,154,58,56));
        	explosionSound = Gdx.audio.newSound(Gdx.files.internal("bomb.mp3"));
        	Texture nave = loadTexture("naves.png");
        	navesTextureRegion = new TextureRegion(nave, 12, 20);
    	}
    	public static void playSound(Sound sound) {
        	sound.play(1);
    	}
	}

Next, change the `MissileCommand` class. Write the following code in our `MissileCommand.java` file. Use the comments in this code to help understand it.

::

	package org.moe.libgdxmissilecommand;
	import com.badlogic.gdx.Game;
	import com.badlogic.gdx.Gdx;
	import com.badlogic.gdx.graphics.g2d.SpriteBatch;
	import org.moe.libgdxmissilecommand.screens.MainMenuScreen;
	// Main game class
	public class MissileCommand extends Game {
    	// used by all screens
    	public SpriteBatch batcher;
    	@Override
    	public void create () {
        	Gdx.input.setCatchBackKey(true);
        	batcher = new SpriteBatch();
        	// Load resources
        	Assets.load();
        	// Draw main menu
        	setScreen(new MainMenuScreen(this));
    	}
    	@Override
    	public void render() {
        	super.render();
    	}
	}

Next create package "screens" for all game screens and create class `MainMenuScreen` for the main menu.

::

	package org.moe.libgdxmissilecommand.screens;
	import com.badlogic.gdx.Gdx;
	import com.badlogic.gdx.Input;
	import com.badlogic.gdx.ScreenAdapter;
	import com.badlogic.gdx.graphics.GL20;
	import com.badlogic.gdx.graphics.OrthographicCamera;
	import com.badlogic.gdx.graphics.g2d.Sprite;
	import com.badlogic.gdx.math.Vector3;
	import org.moe.libgdxmissilecommand.MissileCommand;
	import org.moe.libgdxmissilecommand.Assets;
	public class MainMenuScreen extends ScreenAdapter {
    	MissileCommand game;
    	OrthographicCamera guiCam;
    	Sprite startButton;
    	Sprite creditsButton;
    	Vector3 touchPoint;
    	public MainMenuScreen (MissileCommand game) {
        	this.game = game;
        	// initialize camera
        	guiCam = new OrthographicCamera(Assets.screenWidth, Assets.screenHeight);
        	guiCam.position.set(Assets.screenWidth / 2, Assets.screenHeight / 2, 0);
        	// Create buttons
        	startButton = new Sprite(Assets.startButtonTextureRegion);
        	startButton.setPosition(Assets.screenWidth / 2 - startButton.getWidth() / 2, startButton.getHeight() * 2.5f);
        	creditsButton = new Sprite(Assets.creditsButtonTextureRegion);
        	creditsButton.setPosition(Assets.screenWidth / 2 - creditsButton.getWidth() / 2, creditsButton.getHeight());
        	touchPoint = new Vector3();
    	}
    	// Find events
    	public void update () {
        	if (Gdx.input.isKeyPressed(Input.Keys.BACK)) {
            	Gdx.app.exit();
        	}
        	if (Gdx.input.justTouched()) {
            	guiCam.unproject(touchPoint.set(Gdx.input.getX(), Gdx.input.getY(), 0));
            	// Update screen
            	if (startButton.getBoundingRectangle().contains(touchPoint.x, touchPoint.y)) {
                	game.setScreen(new MissleCommandGameScreen(game));
                	return;
            	}
            	if (creditsButton.getBoundingRectangle().contains(touchPoint.x, touchPoint.y)) {
                	game.setScreen(new CreditsScreen(game));
                	return;
            	}
        	}
    	}
    	// Draw elements
    	public void draw () {
        	GL20 gl = Gdx.gl;
        	gl.glClearColor(1, 0, 0, 1);
        	gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        	guiCam.update();
        	game.batcher.setProjectionMatrix(guiCam.combined);
        	game.batcher.disableBlending();
        	game.batcher.begin();
        	game.batcher.draw(Assets.backgroundRegionMenu, 0, 0, Assets.screenWidth, Assets.screenHeight);
        	game.batcher.end();
        	game.batcher.enableBlending();
        	game.batcher.begin();
        	startButton.draw(game.batcher);
        	creditsButton.draw(game.batcher);
        	game.batcher.end();
    	}
    	@Override
    	public void render (float delta) {
        	update();
        	draw();
    	}
	}

Create the class `CreditsScreen` with some information about our game.

::

	package org.moe.libgdxmissilecommand.screens;
	import com.badlogic.gdx.Gdx;
	import com.badlogic.gdx.Input;
	import com.badlogic.gdx.ScreenAdapter;
	import com.badlogic.gdx.graphics.GL20;
	import com.badlogic.gdx.graphics.OrthographicCamera;
	import com.badlogic.gdx.graphics.g2d.BitmapFont;
	import com.badlogic.gdx.graphics.g2d.Sprite;
	import com.badlogic.gdx.math.Vector3;
	import org.moe.libgdxmissilecommand.MissileCommand;
	import org.moe.libgdxmissilecommand.Assets;
	public class CreditsScreen extends ScreenAdapter {
    	MissileCommand game;
    	OrthographicCamera guiCam;
    	Sprite backButton;
    	Vector3 touchPoint;
    	BitmapFont font;
    	public CreditsScreen(MissileCommand game) {
        	this.game = game;
        	font = new BitmapFont(Assets.fontFile);
        	font.getData().setScale(0.7f);
        	guiCam = new OrthographicCamera(Assets.screenWidth, Assets.screenHeight);
        	guiCam.position.set(Assets.screenWidth / 2, Assets.screenHeight / 2, 0);
        	backButton = new Sprite(Assets.backButtonTextureRegion);
        	backButton.setPosition(Assets.screenWidth / 2 - backButton.getWidth() / 2, backButton.getHeight());
        	touchPoint = new Vector3();
    	}
    	public void update () {
        	if (Gdx.input.justTouched()) {
            	guiCam.unproject(touchPoint.set(Gdx.input.getX(), Gdx.input.getY(), 0));
            	if (backButton.getBoundingRectangle().contains(touchPoint.x, touchPoint.y)) {
                	game.setScreen(new MainMenuScreen(game));
                	return;
            	}
        	}
        	if (Gdx.input.isKeyPressed(Input.Keys.BACK)){
            	return;
        	}
    	}
    	public void draw () {
        	GL20 gl = Gdx.gl;
        	gl.glClearColor(1, 0, 0, 1);
        	gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        	guiCam.update();
        	game.batcher.setProjectionMatrix(guiCam.combined);
        	game.batcher.disableBlending();
        	game.batcher.begin();
        	game.batcher.draw(Assets.backgroundRegionMenu, 0, 0, Assets.screenWidth, Assets.screenHeight);
        	game.batcher.end();
        	game.batcher.enableBlending();
        	game.batcher.begin();
        	backButton.draw(game.batcher);
        	font.draw(game.batcher, "Programmer: Matheus Palheta\n\nGame Design: Jucimar Jr", 200, 320);
        	game.batcher.end();
    	}
    	@Override
    	public void render (float delta) {
        	update();
        	draw();
    	}
    	@Override
    	public void pause () {
        	//Settings.save();
    	}
	}

Create the main game screen class `MissleCommandGameScreen`.

::

	package org.moe.libgdxmissilecommand.screens;
	import com.badlogic.gdx.Gdx;
	import com.badlogic.gdx.ScreenAdapter;
	import com.badlogic.gdx.graphics.GL20;
	import com.badlogic.gdx.graphics.OrthographicCamera;
	import com.badlogic.gdx.graphics.g2d.BitmapFont;
	import com.badlogic.gdx.graphics.g2d.Sprite;
	import com.badlogic.gdx.math.Rectangle;
	import com.badlogic.gdx.math.Vector3;
	import org.moe.libgdxmissilecommand.Assets;
	import org.moe.libgdxmissilecommand.MissileCommand;
	import org.moe.libgdxmissilecommand.models.City;
	import org.moe.libgdxmissilecommand.models.GameObject;
	import org.moe.libgdxmissilecommand.models.Nave;
	import java.util.ArrayList;
	public class MissleCommandGameScreen extends ScreenAdapter {
    	private MissileCommand game;
    	private OrthographicCamera guiCam;
    	private BitmapFont fontTime;
    	private BitmapFont fontTitle;
    	private int levelBackgroung = 0;
    	private long lastAttackTime = 0;
    	private float time = 0;
    	private boolean playing = true;
    	private Sprite pauseButton;
    	private Sprite backButton;
    	private Vector3 touchPoint;
    	private int wave = 1;
    	private long verNaves = 0;
    	private long score = 0;
    	private ArrayList<org.moe.libgdxmissilecommand.models.Missile> missiles = new ArrayList<>();
    	private ArrayList<Nave> naves = new ArrayList<>();
    	City[] cities = new City[6];
    	org.moe.libgdxmissilecommand.models.Player player;
    	public MissleCommandGameScreen(MissileCommand game) {
        	this.game = game;
        	fontTime = new BitmapFont(Assets.fontFile);
        	fontTime.getData().setScale(0.5f);
        	fontTitle = new BitmapFont(Assets.fontFile);
        	fontTitle.getData().setScale(0.7f);

                // Initialize camera
        	guiCam = new OrthographicCamera(Assets.screenWidth, Assets.screenHeight);
        	guiCam.position.set(Assets.screenWidth / 2, Assets.screenHeight / 2, 0);

                // Create buttons
        	pauseButton = new Sprite(Assets.pauseButtonTextureRegion);
        	pauseButton.setPosition(Assets.screenWidth - (pauseButton.getWidth() + 2), 5);
        	backButton = new Sprite(Assets.backButtonTextureRegion);
        	backButton.setPosition(Assets.screenWidth - (backButton.getWidth() + 2), 2);
        	touchPoint = new Vector3();
                // Create player
        	player = new org.moe.libgdxmissilecommand.models.Player();
        	player.setPosition(Assets.screenWidth / 2, Assets.screenHeight / 24);

                // Create cities
        	City.resetCounter();
        	for (int i = 0; i < cities.length; i++) {
            	cities[i] = new City();
        	}
    	}

        // Draw elements
    	private void draw() {
        	GL20 gl = Gdx.gl;
        	gl.glClearColor(1, 0, 0, 1);
        	gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
        	guiCam.update();
        	game.batcher.setProjectionMatrix(guiCam.combined);
        	game.batcher.begin();
        	game.batcher.draw(Assets.levelsBackgroundsTextureRegions[levelBackgroung], 0, 0, Assets.screenWidth, Assets.screenHeight);
        	game.batcher.end();
        	game.batcher.enableBlending();
        	if (playing)
            	checkCollisions();
        	game.batcher.begin();
        	float dt = Gdx.graphics.getDeltaTime();
        	for (City city : cities) {
            	if (playing)
                	city.update(dt);
            	city.draw(game.batcher);
        	}
        	if (playing) {
            	time -= dt;
            	if (time > 20 / wave && (System.currentTimeMillis() - verNaves > 5000) && City.getCityCounter() > 0) {
                	addNaves();
            	}
        	}
        	int printTime = (int) time;
        	if (printTime < 0)
            	printTime = 0;
        	fontTime.draw(game.batcher, "Time: " + String.valueOf(printTime) + "s",
                	Assets.screenWidth - 150, Assets.screenHeight - 25);
        	fontTime.draw(game.batcher, "Score: " + String.valueOf(score),
                	2, Assets.screenHeight - 25);
        	for(int i = 0; i < missiles.size(); i++) {
            	org.moe.libgdxmissilecommand.models.Missile missile = missiles.get(i);
            	if (missile.isAlive()) {
                	if (playing)
                    	missile.update(dt);
                	missile.draw(game.batcher);
            	} else {
                	missiles.remove(i);
                	i--;
            	}
        	}
        	player.draw(game.batcher);
        	for(int i = 0; i < naves.size(); i++) {
            	Nave nave = naves.get(i);
            	if (nave.isAlive()) {
                	if (playing)
                    	nave.update(dt);
                	nave.draw(game.batcher);
            	} else {
                	naves.remove(i);
                	i--;
            	}
        	}
        	if (playing) {
            	if (time <= 0) {
                	fontTitle.draw(game.batcher, "Wave " + String.valueOf(wave) +
                        	" Starts in " + String.valueOf((int)(3 + time)) + "s",
                        	230, 240);
                	if (time < -3) {
                    	time = 60;
                    	wave++;
                    	levelBackgroung = (wave - 2) % 4;
                	}
            	}
            	pauseButton.draw(game.batcher);
        	} else {
            	if (City.getCityCounter() > 0) {
                	fontTitle.draw(game.batcher, "Touch the screen to resuming the game",
                        	100, 320 + fontTitle.getLineHeight());
                	fontTitle.draw(game.batcher, "Or press back button to exit in the main menu",
                        	70, 320 - fontTitle.getLineHeight());
            	} else {
                	fontTitle.draw(game.batcher, "You Lose!",
                        	320, 320 + fontTitle.getLineHeight());
                	fontTitle.draw(game.batcher, "Score: " + String.valueOf(score),
                        	320, 320 - fontTitle.getLineHeight());
            	}
            	backButton.draw(game.batcher);
        	}
        	fontTime.draw(game.batcher, "fps: " + Gdx.graphics.getFramesPerSecond(), 0, 0);
        	game.batcher.end();
    	}

        // Check events
    	private void update() {
        	if (City.getCityCounter() <= 0) {
            	playing = false;
        	}
        	if (Gdx.input.justTouched()) {
            	guiCam.unproject(touchPoint.set(Gdx.input.getX(), Gdx.input.getY(), 0));
            	if (pauseButton.getBoundingRectangle().contains(touchPoint.x, touchPoint.y) && playing) {
                	playing = false;
                	return;
            	}
            	if (backButton.getBoundingRectangle().contains(touchPoint.x, touchPoint.y)) {
                	game.setScreen(new MainMenuScreen(game));
                	return;
            	}
            	if (!playing) {
                	if (City.getCityCounter() > 0)
                    	playing = true;
                	return;
            	}
            	if (System.currentTimeMillis() - lastAttackTime > 450 && touchPoint.y >= player.getY()) {
                	lastAttackTime = System.currentTimeMillis();
                	missiles.add(new org.moe.libgdxmissilecommand.models.Missile());
                	missiles.get(missiles.size() - 1).detectTarget(touchPoint.x, touchPoint.y);
                	player.setRotation(missiles.get(missiles.size() - 1).getRotation());
            	}
        	}
    	}

        // Add new naves
    	private void addNaves() {
        	naves.add(new Nave(wave));
        	naves.add(new Nave(wave));
        	naves.add(new Nave(wave));
        	verNaves = System.currentTimeMillis();
    	}
    	@Override
    	public void render (float delta) {
        	update();
        	draw();
    	}
        // Check all collisions in the game
    	private void checkCollisions() {
        	for(int i = 0; i < naves.size(); i++) {
            	for (City city : cities) {
                	if (isCollision(naves.get(i), city)) {
                    	naves.get(i).kill();
                    	city.kill();
                	}
            	}
            	for(int j = 0; j < missiles.size(); j++) {
                	if (isCollision(naves.get(i), missiles.get(j)) && naves.get(i).kill()) {
                    	score++;
                    	missiles.get(j).kill();
                	}
            	}
        	}
    	}

        // Check collision
    	private <T extends GameObject> boolean isCollision(T obj1, T obj2) {
        	Rectangle r1 = obj1.collisionRectangle();
        	Rectangle r2 = obj2.collisionRectangle();
        	return !(r1 == null || r2 == null) && r2.overlaps(r1);
    	}
	}

We created all the screens for our game. So now we should create some models such as Player, Naves and others for our game. Create a new package `models` and create the base class `GameObject` for all objects in our game.

::

	package org.moe.libgdxmissilecommand.models;
	import com.badlogic.gdx.graphics.g2d.Sprite;
	import com.badlogic.gdx.graphics.g2d.TextureRegion;
	import com.badlogic.gdx.math.Rectangle;
	public class GameObject extends Sprite {
    	protected boolean alive = true;
    	protected float explosionTime;
    	GameObject(TextureRegion region) {
        	super(region);
        	explosionTime = -1;
    	}

        // Check object
    	public boolean isAlive() {
        	return alive;
    	}

        // update object
    	public void update(float deltaTime) {}

        // kill object
    	public boolean kill() {
        	if (Float.compare(explosionTime, -1) == 0) {
            	explosionTime = -100;
            	return true;
        	}
        	return false;
    	}

        // get collision rectangle for object
    	public Rectangle collisionRectangle() {
        	if (!alive) {
            	return null;
        	}
        	return getBoundingRectangle();
    	}
	}

Create the `Player` class.

::

	package org.moe.libgdxmissilecommand.models;
	import com.badlogic.gdx.graphics.g2d.Batch;
	import com.badlogic.gdx.graphics.g2d.Sprite;
	import org.moe.libgdxmissilecommand.Assets;
	public class Player extends GameObject {
    	private Sprite playerBase;
    	public Player() {
        	super(Assets.playerGunTextureRegion);
        	playerBase = new Sprite(Assets.playerBaseTextureRegion);
        	setOrigin(getWidth() / 2, 0);
    	}
    	@Override
    	public void setPosition(float x, float y) {
        	// Need override only for playerBase sprite
        	super.setPosition(x - getWidth() / 2, y + 10);
        	playerBase.setPosition(x - (playerBase.getWidth() / 2), y);
    	}
    	@Override
    	public void draw(Batch batch) {
        	// Need override only for playerBase sprite
        	super.draw(batch);
        	playerBase.draw(batch);
    	}
	}

Create the `Missile` class.

::

	package org.moe.libgdxmissilecommand.models;
	import com.badlogic.gdx.graphics.g2d.Batch;
	import com.badlogic.gdx.graphics.g2d.TextureRegion;
	import com.badlogic.gdx.math.Vector2;
	import org.moe.libgdxmissilecommand.Assets;
	public class Missile extends GameObject {
        // Speed of missile
    	private final float speed = 600.0f;
    	private float targetY;
    	public Missile() {
        	super(Assets.missileTextureRegion);
        	setPosition(Assets.screenWidth / 2, Assets.screenHeight / 24 + 10);

                // Start sound
        	Assets.playSound(Assets.missileSound);
        	targetY = 0;
    	}

        // Detect missile target
    	public void detectTarget(float x, float y) {
        	targetY = y;
        	Vector2 tempVector = new Vector2(x, y);
        	setRotation(tempVector.sub(this.getX(), this.getY()).angle() - 90);
    	}
    	@Override
    	public void update(float deltaTime) {
                // Move missile
        	if (getY() > targetY || getX() < 0 || getX() > Assets.screenWidth || explosionTime >= 0) {
            	explosionTime += deltaTime;
            	return;
        	}
        	float hypotenuse = speed*deltaTime;
        	float shiftY = (float) Math.abs((hypotenuse * Math.cos(getRotation() * Math.PI/180)));
        	float shiftX = (float) Math.abs((hypotenuse * Math.sin(getRotation() * Math.PI/180)));
        	if (Math.sin(getRotation() * Math.PI / 180) > 0) {
            	shiftX = -shiftX;
        	}
        	setPosition(getX() + shiftX, getY() + shiftY);
    	}
    	@Override
    	public void draw(Batch batch) {
        	if (getY() > targetY || getX() < 0 || getX() > Assets.screenWidth || Float.compare(explosionTime, -1) != 0) {
                        // Draw explosion animation
            	if (explosionTime < 0) {
                	explosionTime = 0;
                	Assets.playSound(Assets.explosionSound);
            	}
            	TextureRegion keyFrame = Assets.explosionAnimation.getKeyFrame(explosionTime, false);
            	batch.draw(keyFrame, getX() - 74 / 2, getY() - 76 / 2, 74, 76);
            	if (Assets.explosionAnimation.isAnimationFinished(explosionTime))
                	alive = false;
        	} else {
                        // Draw missile
            	super.draw(batch);
        	}
    	}
	}

Now create the class `Nave`.

::

	package org.moe.libgdxmissilecommand.models;
	import com.badlogic.gdx.graphics.g2d.Batch;
	import com.badlogic.gdx.graphics.g2d.TextureRegion;
	import org.moe.libgdxmissilecommand.Assets;
	import java.security.SecureRandom;
	public class Nave extends GameObject {
    	private float velX = 0, velY = 0;
    	public Nave(int wave) {
        	super(Assets.navesTextureRegion);
        	SecureRandom random = new SecureRandom();
                // Init position
        	int posX = random.nextInt((int) Assets.screenWidth);
        	setPosition(posX, Assets.screenHeight);
        	// Calculate init rotation
                	float angle;
        	if (posX < 400) {
            	angle = -random.nextFloat() * 45;
            	velX = (float) (Math.sin(angle * Math.PI/180) * (wave / 2));
            	velY = (float) (Math.cos(angle * Math.PI/180) * (wave / 2));
        	} else {
            	angle = random.nextFloat() * 45;
            	velX = (float) (Math.sin(angle * Math.PI/180) * (wave / 2));
            	velY = (float) (Math.cos(angle * Math.PI/180) * (wave / 2));
        	}
        	setRotation(-angle);
    	}
    	@Override
    	public void update(float deltaTime) {
                // Move nave
        	if (getY() < 30 || explosionTime >= 0) {
            	explosionTime += deltaTime;
            	return;
        	}
        	setPosition(getX() - velX, getY() - velY);
    	}
    	@Override
    	public void draw(Batch batch) {
        	if (getY() < 30 || Float.compare(explosionTime, -1) != 0) {
                        // Draw explosion animation
            	if (explosionTime < 0) {
                	explosionTime = 0;
                	Assets.playSound(Assets.explosionSound);
            	}
            	TextureRegion keyFrame = Assets.explosionAnimation.getKeyFrame(explosionTime, false);
            	batch.draw(keyFrame, getX() - 74 / 2, getY() - 76 / 2, 74, 76);
            	if (Assets.explosionAnimation.isAnimationFinished(explosionTime))
                	alive = false;
        	} else {
                        // Draw nave
            	super.draw(batch);
        	}
    	}
	}

And also create class `City` for cities.

::

	package org.moe.libgdxmissilecommand.models;
	import com.badlogic.gdx.graphics.g2d.Batch;
	import com.badlogic.gdx.graphics.g2d.TextureRegion;
	import org.moe.libgdxmissilecommand.Assets;
	import java.security.SecureRandom;
	public class City extends GameObject {
        // Cities counter
    	static long cityCounter = 0;
    	public City() {
                // Take random texture
        	super(Assets.citiesTextureRegions[new SecureRandom().nextInt(6)]);
                // Init position
        	if (cityCounter < 3) {
            	setPosition(50  + ((Assets.screenWidth - 200) / 6) * cityCounter, Assets.screenHeight / 24);
        	} else {
            	setPosition(50  + ((Assets.screenWidth - 200) / 6) * cityCounter + 120, Assets.screenHeight / 24);
        	}
        	cityCounter++;
    	}

        // Reset counter
    	public static void resetCounter() {
        	cityCounter = 0;
    	}

        // Get counter
    	public static long getCityCounter() {
        	return cityCounter;
    	}
    	@Override
    	public void update(float deltaTime) {
                // Update explosion animation
        	if (explosionTime >= 0)
            	explosionTime += deltaTime;
    	}
    	@Override
    	public void draw(Batch batch) {
        	if (Float.compare(explosionTime, -1) != 0) {
                        // Draw animation
            	if (explosionTime < 0) {
                	explosionTime = 0;
                	Assets.playSound(Assets.explosionSound);
            	}
            	TextureRegion keyFrame = Assets.citiesDestroyAnimation.getKeyFrame(explosionTime, false);
            	if (Assets.citiesDestroyAnimation.getKeyFrameIndex(explosionTime) == 1) {
                	batch.draw(keyFrame, getX(), getY(), getWidth(), 15);
                	if (isAlive())
                    	cityCounter--;
                	alive = false;
            	} else {
                	batch.draw(keyFrame, getX(), getY(), getWidth(), getHeight());
            	}
        	} else {
                        // Draw city
            	super.draw(batch);
        	}
    	}
	}

That completes the common part of our application! Now we can start to develop the Android and/or iOS parts of our game.

Android Code Part
=================

All configuartion is already done by the generator.

Asset Part
=================


Finally, add images, sounds and others asset files for our game. You can download these files from `here https://github.com/jucimarjr/html5games/tree/master/cocos2d/MissileCommand/assets`_ (All resources are distributed under MIT license). After you download these files, copy them to the "assets" directory. Rename the files a.png-g.png to city[1...6].png.

.. image:: images/libgdx5.png

Congratulations! We completed our Android game. Now we can build and run the game! You can see the running app in the screen shot below.

.. image:: images/libgdx6.png


iOS Code Part
=============

The code is already fully functional generated.

Now we will modify the Xcode project. Right-click its name and select Multi-OS Engine > Open Project in Xcode.

.. image:: images/libgdx7.png

The Xcode project will be opened and we should see the next screen:

.. image:: images/libgdx8.png

Than, add the necessary frameworks to our application.

.. image:: images/libgdx9.png

.. image:: images/libgdx10.png

.. image:: images/libgdx11.png

.. image:: images/libgdx12.png

Add all xcframeworks available.

Congratulations! We completed our iOS game and our application. You can see iOS game screenshot below.

.. image:: images/libgdx14.png


Debug Your App
==============

We can now explore how you can debug your libGDX application. The libGDX debug process is not specific, so we can debug our libGDX game as usual Multi-OS Engine app. To begin, set some breakpoints.

For example, set two breakpoints in our common code part. First, set a breakpoint at the start of game creating function (`create()`) at line 15 (`MissleCommand.java:MissleCommand.create():15`).

.. image:: images/libgdx20.png

Set the second breakpoint in file `MainMenuScreen.java`  line 55 (start of draw function). (`MainMenuScreen. MainMenuScreen.draw():55`).

.. image:: images/libgdx21.png

Now we can run our application with debugging. While debugging, use all opportunities to debug your code such as Step Over, Step Into, Resume program. Also you can use stack trace to help debug your application.

.. image:: images/libgdx22.png

Use a stack trace to see values of variables on a previous step. You can see it below.

.. image:: images/libgdx23.png

You can download all Multi-OS Engine samples `here (Java) <https://github.com/multi-os-engine/moe-samples-java>`_ and `here (Kotlin) <https://github.com/multi-os-engine/moe-samples-kotlin>`_.


Summary and Resources
=====================

LibGDX development with the Multi-OS Engine has many advantages, including:

•   The biggest part of application is the common part.
•   The common part uses familiar Java syntax.
•   You can debug two targets side-by-side using the powerful iOS simulator and Android emulator.