Make afterburnerModel cyan

- When acceleration results in a velocity vector in the opposite direction
of the current velocity, zero out velocity

- Moved maxVelocity from VelocityComponent to AccelerationComponent

-

android/assets/Retro_Font.fnt

@@ -0,0 +1,102 @@
+info face="Retro Gaming" size=32 bold=0 italic=0 charset="" unicode=0 stretchH=100 smooth=1 aa=1 padding=1,1,1,1 spacing=-1,-1
+common lineHeight=42 base=32 scaleW=256 scaleH=256 pages=1 packed=0
+page id=0 file="Retro_Font.png"
+chars count=97
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+kernings count=0

core/src/com/me/asteroids/Asteroids.java

@@ -12,8 +12,9 @@ public class Asteroids extends ApplicationAdapter {
 
     @Override
     public void create() {
-        graphics = new Graphics(Constants.WIDTH, Constants.HEIGHT);
+        graphics = new Graphics();
         graphics.initialize();
+        updateViewport(Gdx.graphics.getWidth(), Gdx.graphics.getHeight());
 
         game = new Game();
         game.setNextScreen(new GameScreen(graphics));
@@ -33,7 +34,12 @@ public class Asteroids extends ApplicationAdapter {
 
     @Override
     public void resize(int width, int height) {
-        graphics.setScreenSize(width, height);
+        updateViewport(width, height);
+    }
+
+    private void updateViewport(int width, int height) {
+        Constants.updateDimensions(width, height);
+        graphics.updateViewport(Constants.WIDTH, Constants.HEIGHT, Constants.getUIWidth(), Constants.getUIHeight());
     }
 
 }

core/src/com/me/asteroids/Components.java

@@ -0,0 +1,44 @@
+package com.me.asteroids;
+
+import com.me.asteroids.components.AccelerationComponent;
+import com.me.asteroids.components.AsteroidComponent;
+import com.me.asteroids.components.BulletTagComponent;
+import com.me.asteroids.components.ColliderTagComponent;
+import com.me.asteroids.components.DebrisTagComponent;
+import com.me.asteroids.components.DecayComponent;
+import com.me.asteroids.components.GameDataComponent;
+import com.me.asteroids.components.ModelComponent;
+import com.me.asteroids.components.PlayerComponent;
+import com.me.asteroids.components.PositionComponent;
+import com.me.asteroids.components.VelocityComponent;
+import com.me.common.ecs.ComponentMapper;
+
+public class Components {
+
+    public static final ComponentMapper<AccelerationComponent> ACCELERATION;
+    public static final ComponentMapper<AsteroidComponent> ASTEROID;
+    public static final ComponentMapper<BulletTagComponent> BULLET;
+    public static final ComponentMapper<ColliderTagComponent> COLLIDER;
+    public static final ComponentMapper<DebrisTagComponent> DEBRIS;
+    public static final ComponentMapper<DecayComponent> DECAY;
+    public static final ComponentMapper<GameDataComponent> GAME_DATA;
+    public static final ComponentMapper<ModelComponent> MODEL;
+    public static final ComponentMapper<PlayerComponent> PLAYER;
+    public static final ComponentMapper<PositionComponent> POSITION;
+    public static final ComponentMapper<VelocityComponent> VELOCITY;
+
+
+    static {
+        ACCELERATION = ComponentMapper.getFor(AccelerationComponent.class);
+        ASTEROID = ComponentMapper.getFor(AsteroidComponent.class);
+        BULLET = ComponentMapper.getFor(BulletTagComponent.class);
+        COLLIDER = ComponentMapper.getFor(ColliderTagComponent.class);
+        DEBRIS = ComponentMapper.getFor(DebrisTagComponent.class);
+        DECAY = ComponentMapper.getFor(DecayComponent.class);
+        GAME_DATA = ComponentMapper.getFor(GameDataComponent.class);
+        MODEL = ComponentMapper.getFor(ModelComponent.class);
+        PLAYER = ComponentMapper.getFor(PlayerComponent.class);
+        POSITION = ComponentMapper.getFor(PositionComponent.class);
+        VELOCITY = ComponentMapper.getFor(VelocityComponent.class);
+    }
+}

core/src/com/me/asteroids/Constants.java

@@ -2,19 +2,50 @@ package com.me.asteroids;
 
 import com.me.common.Random;
 
-public class Constants {
+public final class Constants {
 
     public static final boolean DEBUG = false;
 
     public static final Random rand = new Random();
 
-    public static final int WIDTH = 800;
-    public static final int HEIGHT = 600;
-
-    public static final int HALF_WIDTH = WIDTH / 2;
-    public static final int HALF_HEIGHT = HEIGHT / 2;
-
     public static final float ASTEROID_SPAWN_DELAY = 1f;
     public static final int ASTEROID_SPAWN_COUNT = 4;
+    public static final int NEW_LIFE_SCORE = 10000;
+
+    public static int SCREEN_WIDTH;
+    public static int SCREEN_HEIGHT;
+
+    public static final float HEIGHT = 10f;
+    public static float WIDTH;
+
+    public static final float HALF_HEIGHT = HEIGHT / 2;
+    public static float HALF_WIDTH;
+
+    public static float getUIWidth() {
+        return SCREEN_WIDTH * getUIScale();
+    }
+
+    public static float getUIHeight() {
+        return SCREEN_HEIGHT * getUIScale();
+    }
+
+    public static float getHalfUIWidth() {
+        return getUIWidth() / 2;
+    }
+
+    public static float getHalfUIHeight() {
+        return getUIHeight() / 2;
+    }
+
+    public static float getUIScale() {
+        return 1.5f / (Math.min(SCREEN_HEIGHT, SCREEN_WIDTH) / 400f);
+    }
+
+    public static void updateDimensions(int screenWidth, int screenHeight) {
+        SCREEN_WIDTH = screenWidth;
+        SCREEN_HEIGHT = screenHeight;
+        WIDTH = (HEIGHT / SCREEN_HEIGHT) * SCREEN_WIDTH;
+        HALF_WIDTH = WIDTH / 2;
+    }
 
 }

core/src/com/me/asteroids/EntityFactory.java

@@ -5,9 +5,9 @@ import com.badlogic.gdx.math.MathUtils;
 import com.badlogic.gdx.math.Vector2;
 import com.me.asteroids.components.AccelerationComponent;
 import com.me.asteroids.components.AsteroidComponent;
-import com.me.asteroids.components.BulletComponent;
+import com.me.asteroids.components.BulletTagComponent;
-import com.me.asteroids.components.ColliderComponent;
+import com.me.asteroids.components.ColliderTagComponent;
-import com.me.asteroids.components.DebrisComponent;
+import com.me.asteroids.components.DebrisTagComponent;
 import com.me.asteroids.components.DecayComponent;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.PlayerComponent;
@@ -21,6 +21,10 @@ import com.me.common.ecs.Entity;
 
 import java.util.Arrays;
 
+import static com.me.asteroids.Components.ASTEROID;
+import static com.me.asteroids.Components.MODEL;
+import static com.me.asteroids.Components.POSITION;
+import static com.me.asteroids.Components.VELOCITY;
 import static com.me.asteroids.Constants.rand;
 
 public class EntityFactory {
@@ -30,7 +34,9 @@ public class EntityFactory {
     private static final Vector2 tmpA = new Vector2();
     private static final Vector2 tmpB = new Vector2();
 
-    private static final ColliderComponent COLLIDER = new ColliderComponent();
+    private static final ColliderTagComponent COLLIDER_TAG = new ColliderTagComponent();
+    private static final DebrisTagComponent DEBRIS_TAG = new DebrisTagComponent();
+    private static final BulletTagComponent BULLET_TAG = new BulletTagComponent();
 
     private static Entity createEntity(Engine engine) {
         Entity entity = engine.createEntity();
@@ -41,35 +47,39 @@ public class EntityFactory {
     }
 
     public static Entity createPlayer(Engine engine) {
-        PositionComponent position = new PositionComponent();
+        VelocityComponent velocity = new VelocityComponent(0f, 0f, 0f);
-        position.position = new Vector2(Constants.HALF_WIDTH, Constants.HALF_HEIGHT);
-        position.rotation = 90;
 
-        VelocityComponent velocity = new VelocityComponent();
+        ModelComponent playerModel = new ModelComponent(new PolygonModel(Color.WHITE));
-        velocity.velocity = new Vector2(0f, 0f);
+        playerModel.setVertices(new float[]{
-        velocity.maxVelocity = 400f;
+                0f, 0.5f,         // tip
-
+                -5/16f, -0.5f,     // bottom left
-        ModelComponent model = new ModelComponent();
+                -1/8f, -5/16f,     // indent
-        model.model = new PolygonModel(Color.WHITE);
+                1/8f, -5/16f,      // indent
-        model.model.setVertices(new float[]{
+                5/16f, -0.5f,      // bottom right
-                0f, 4f,         // tip
-                -2.5f, -4f,     // bottom left
-                -1f, -2.5f,     // indent
-                1f, -2.5f,      // indent
-                2.5f, -4f,      // bottom right
         });
-        model.model.setScale(5);
 
-        AccelerationComponent accel = new AccelerationComponent();
+        ModelComponent afterburnerModel = new ModelComponent(new LineModel(Color.CYAN));
-        accel.acceleration = new Vector2(0, 1f);
+        afterburnerModel.setVertices(new float[]{
+                -2/16f, -5/16f,
+                0f, -0.8f,
+                2/16f, -5/16f
+        });
 
         Entity player = createEntity(engine);
-        player.addComponent(position);
+        Entity afterBurner = createEntity(engine);
+
+        player.addComponent(new PositionComponent(Constants.HALF_WIDTH, Constants.HALF_HEIGHT, 90));
         player.addComponent(velocity);
-        player.addComponent(model);
+        player.addComponent(playerModel);
-        player.addComponent(accel);
+        player.addComponent(new AccelerationComponent(10f));
-        player.addComponent(COLLIDER);
+        player.addComponent(COLLIDER_TAG);
-        player.addComponent(new PlayerComponent());
+        player.addComponent(new PlayerComponent(afterBurner));
+        player.setTag("PLAYER");
+
+        afterBurner.addComponent(new PositionComponent(Constants.HALF_WIDTH, Constants.HALF_HEIGHT, 90));
+        afterBurner.addComponent(velocity);
+        afterBurner.addComponent(afterburnerModel);
+
         return player;
     }
 
@@ -103,35 +113,31 @@ public class EntityFactory {
     }
 
     public static Entity[] createDebris(Engine engine, Entity entity) {
-        Vector2 playerVelocity = entity.getComponent(VelocityComponent.class).velocity;
+        Vector2 playerVelocity = VELOCITY.get(entity).velocity;
-        PositionComponent playerPosition = entity.getComponent(PositionComponent.class);
+        PositionComponent playerPosition = POSITION.get(entity);
-        LineModel[] models = getLineModels(entity.getComponent(ModelComponent.class).model);
+        LineModel[] models = getLineModels(MODEL.get(entity).model);
-        Vector2 explosionCenter = tmp.set(playerPosition.position).sub(Utils.setUnitVectorAngle(tmp2, playerPosition.rotation).scl(5));
+
+        Vector2 explosionCenter = tmp.set(playerPosition.position).sub(Utils.setUnitVectorAngle(tmp2, playerPosition.rotation).scl(0.125f));
 
         Entity[] entities = new Entity[models.length];
         for (int i = 0, n = models.length; i < n; i++) {
-            ModelComponent model = new ModelComponent();
+            ModelComponent model = new ModelComponent(models[i]);
-            model.model = models[i];
-
-            PositionComponent position = new PositionComponent();
-            position.position = new Vector2(model.model.getPosition());
-            position.rotation = 90;
 
             VelocityComponent velocity = new VelocityComponent();
-            velocity.velocity = new Vector2(models[i].getPosition())
+            velocity.set(new Vector2(models[i].getPosition())
                     .sub(explosionCenter)
                     .nor()                                      // Direction from explosion center to center of piece
                     .rotate(rand.nextFloat(-15, 15))            // Slightly alter the direction each piece flies off in
-                    .scl(rand.nextFloat(75, 100))               // Give each piece a slightly different speed
+                    .scl(rand.nextFloat(2f, 2.5f))              // Give each piece a slightly different speed
-                    .add(tmp2.set(playerVelocity).scl(0.75f));  // Maintain 75% of the player's velocity at impact
+                    .add(tmp2.set(playerVelocity).scl(0.75f))); // Maintain 75% of the player's velocity at impact
             velocity.angularVelocity = rand.nextFloat(-60, 60); // Make each piece spin at a different rate
 
             Entity debris = createEntity(engine);
-            debris.addComponent(position);
+            debris.addComponent(new PositionComponent(new Vector2(model.getPosition()), 90));
             debris.addComponent(velocity);
             debris.addComponent(model);
+            debris.addComponent(DEBRIS_TAG);
             debris.addComponent(new DecayComponent(rand.nextFloat(0.5f, 2.5f)));
-            debris.addComponent(new DebrisComponent());
             entities[i] = debris;
         }
         return entities;
@@ -139,49 +145,37 @@ public class EntityFactory {
 
 
     public static Entity createBullet(Engine engine, Entity player) {
-        float[] modelVertices = player.getComponent(ModelComponent.class).model.getVertices();
+        float[] modelVertices = MODEL.get(player).model.getVertices();
-        float rotation = player.getComponent(PositionComponent.class).rotation;
+        float rotation = POSITION.get(player).rotation;
+
+        PositionComponent position = new PositionComponent(modelVertices[0], modelVertices[1], rotation);
+        ModelComponent model = new ModelComponent(new PolygonModel(Color.YELLOW));
+        model.setVertices(new float[]{
+                1/40f, 0f,
+                -1/40f, 0f,
+                -1/40f, -4/40f,
+                1/40f, -4/40f,
+        });
+        model.setRotation(position.rotation);
+        model.setPosition(position.position);
 
         Vector2 direction = Utils.setUnitVectorAngle(tmp, rotation);
 
-        VelocityComponent velocity = new VelocityComponent();
-        velocity.velocity = new Vector2(direction).scl(500);
-
-        PositionComponent position = new PositionComponent();
-        position.position = new Vector2(modelVertices[0], modelVertices[1]).add(direction.scl(4));
-        position.rotation = rotation;
-
-        ModelComponent model = new ModelComponent();
-        model.model = new PolygonModel(Color.YELLOW);
-        model.model.setVertices(new float[]{
-                1f, 0f,
-                -1f, 0f,
-                -1f, -4f,
-                1f, -4f,
-        });
-        model.model.setRotation(position.rotation);
-        model.model.setPosition(position.position);
-
-
         Entity bullet = createEntity(engine);
         bullet.addComponent(position);
-        bullet.addComponent(velocity);
+        bullet.addComponent(new VelocityComponent(new Vector2(direction).scl(12.5f)));
         bullet.addComponent(model);
-        bullet.addComponent(COLLIDER);
+        bullet.addComponent(COLLIDER_TAG);
-        bullet.addComponent(new BulletComponent());
+        bullet.addComponent(BULLET_TAG);
         return bullet;
     }
 
     public static Entity createAsteroid(Engine engine) {
         // Creates an asteroid entity with position and velocity unset - the AsteroidSpawningSystem
         // is responsible for setting its position and velocity
-        PositionComponent position = new PositionComponent();
+        ModelComponent model = new ModelComponent(new PolygonModel(Color.WHITE));
-        VelocityComponent velocity = new VelocityComponent();
+        float size = rand.nextFloat(1f, 1.75f);
-
+        model.setVertices(new AsteroidFactory()
-        ModelComponent model = new ModelComponent();
-        model.model = new PolygonModel(Color.WHITE);
-        int size = rand.nextInt(45, 75);
-        model.model.setVertices(new AsteroidFactory()
                 .setVertexCount(32)
                 .setSize(size)
                 .setSizeVariation(size * 0.5f)
@@ -189,11 +183,12 @@ public class EntityFactory {
                 .generate());
 
         Entity asteroid = createEntity(engine);
-        asteroid.addComponent(position);
+        asteroid.addComponent(new PositionComponent());
-        asteroid.addComponent(velocity);
+        asteroid.addComponent(new VelocityComponent());
         asteroid.addComponent(model);
-        asteroid.addComponent(COLLIDER);
+        asteroid.addComponent(COLLIDER_TAG);
         asteroid.addComponent(new AsteroidComponent());
+        asteroid.addGroup("ASTEROIDS");
         return asteroid;
     }
 
@@ -207,8 +202,8 @@ public class EntityFactory {
     }
 
     public static Entity[] splitAsteroidIntoChunks(Engine engine, Entity asteroid, int chunkCount, float chunkScale) {
-        Vector2 asteroidVelocity = asteroid.getComponent(VelocityComponent.class).velocity;
+        Vector2 asteroidVelocity = VELOCITY.get(asteroid).velocity;
-        Model asteroidModel = asteroid.getComponent(ModelComponent.class).model;
+        ModelComponent asteroidModel = MODEL.get(asteroid);
         Vector2 asteroidPosition = asteroidModel.getPosition();
         float[] scaledVertices = scaleAndRelativizeVertices(asteroidPosition, asteroidModel.getVertices(), chunkScale);
 
@@ -218,33 +213,27 @@ public class EntityFactory {
 
         Entity[] entities = new Entity[chunkCount];
         for (int i = 0; i < chunkCount; i++) {
-            Vector2 chunkPosition = tmp2.set(asteroidPosition).add(tmp.scl(25));
+            Vector2 chunkPosition = tmp2.set(asteroidPosition).add(tmp.scl(0.5f));
 
-            ModelComponent model = new ModelComponent();
+            ModelComponent model = new ModelComponent(new PolygonModel(asteroidModel.getColor()));
-            model.model = new PolygonModel(asteroidModel.getColor());
+            model.setVertices(Arrays.copyOf(scaledVertices, scaledVertices.length));
-            model.model.setVertices(Arrays.copyOf(scaledVertices, scaledVertices.length));
+            model.setPosition(chunkPosition);
-            model.model.setPosition(chunkPosition);
-
-            PositionComponent position = new PositionComponent();
-            position.position = new Vector2(chunkPosition);
-            position.rotation = 90;
 
             VelocityComponent velocity = new VelocityComponent();
-            velocity.velocity = new Vector2(tmp).nor().rotate(rand.nextFloat(-45, 45)).scl(asteroidVelocity.len() * 1.10f);
+            velocity.set(tmp);
+            velocity.velocity.nor().rotate(rand.nextFloat(-45, 45)).scl(asteroidVelocity.len() * 1.10f);
             velocity.angularVelocity = rand.nextFloat(-30, 30);
 
-            AsteroidComponent asteroidComponent = new AsteroidComponent();
-            asteroidComponent.generation = asteroid.getComponent(AsteroidComponent.class).generation + 1;
-
             angle += angleStep;
             Utils.setUnitVectorAngleRad(tmp, angle);
 
             Entity split = createEntity(engine);
             split.addComponent(model);
-            split.addComponent(position);
+            split.addComponent(new PositionComponent(new Vector2(chunkPosition), 90));
             split.addComponent(velocity);
-            split.addComponent(asteroidComponent);
+            split.addComponent(new AsteroidComponent(ASTEROID.get(asteroid).generation + 1));
-            split.addComponent(COLLIDER);
+            split.addComponent(COLLIDER_TAG);
+            split.addGroup("ASTEROIDS");
             entities[i] = split;
         }
 

core/src/com/me/asteroids/EventFactory.java

@@ -1,22 +1,23 @@
 package com.me.asteroids;
 
-import com.me.asteroids.components.AsteroidComponent;
-import com.me.asteroids.components.BulletComponent;
-import com.me.asteroids.components.PlayerComponent;
 import com.me.asteroids.events.BulletAsteroidCollisionEvent;
 import com.me.asteroids.events.CollisionEvent;
 import com.me.asteroids.events.PlayerASteroidCollisionEvent;
 import com.me.common.ecs.Entity;
 
+import static com.me.asteroids.Components.ASTEROID;
+import static com.me.asteroids.Components.BULLET;
+import static com.me.asteroids.Components.PLAYER;
+
 public class EventFactory {
 
     public static CollisionEvent getNewCollisionEvent(Entity a, Entity b) {
-        boolean isEntityAPlayer = a.hasComponent(PlayerComponent.class);
+        boolean isEntityAPlayer = PLAYER.has(a);
-        boolean isEntityBPlayer = b.hasComponent(PlayerComponent.class);
+        boolean isEntityBPlayer = PLAYER.has(b);
-        boolean isEntityABullet = !isEntityAPlayer && a.hasComponent(BulletComponent.class);
+        boolean isEntityABullet = !isEntityAPlayer && BULLET.has(a);
-        boolean isEntityBBullet = !isEntityBPlayer && b.hasComponent(BulletComponent.class);
+        boolean isEntityBBullet = !isEntityBPlayer && BULLET.has(b);
-        boolean isEntityAAsteroid = !isEntityAPlayer && !isEntityABullet && a.hasComponent(AsteroidComponent.class);
+        boolean isEntityAAsteroid = !isEntityAPlayer && !isEntityABullet && ASTEROID.has(a);
-        boolean isEntityBAsteroid = !isEntityBPlayer && !isEntityBBullet && b.hasComponent(AsteroidComponent.class);
+        boolean isEntityBAsteroid = !isEntityBPlayer && !isEntityBBullet && ASTEROID.has(b);
 
         if (isEntityAAsteroid || isEntityBAsteroid) {
             if (isEntityAPlayer && isEntityBAsteroid) {

core/src/com/me/asteroids/GameMode.java

@@ -0,0 +1,24 @@
+package com.me.asteroids;
+
+public enum GameMode {
+
+    PLAYING,
+    DIED(3f),
+    GAME_OVER(4f),
+    ;
+
+    private final float modeTimer;
+
+    GameMode() {
+        this(0f);
+    }
+
+    GameMode(float modeTimer) {
+        this.modeTimer = modeTimer;
+    }
+
+    public float getTimer() {
+        return modeTimer;
+    }
+
+}

core/src/com/me/asteroids/Graphics.java

@@ -1,63 +1,62 @@
 package com.me.asteroids;
 
 import com.badlogic.gdx.Gdx;
-import com.badlogic.gdx.graphics.Camera;
 import com.badlogic.gdx.graphics.GL20;
 import com.badlogic.gdx.graphics.OrthographicCamera;
+import com.badlogic.gdx.graphics.g2d.SpriteBatch;
 import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
-import com.badlogic.gdx.utils.viewport.FitViewport;
-import com.badlogic.gdx.utils.viewport.Viewport;
 
 public class Graphics {
 
-    private int worldWidth, worldHeight;
+    private OrthographicCamera camera;
-    private int screenWidth, screenHeight;
+    private OrthographicCamera uiCamera;
-
-    private Camera camera;
-    private Viewport viewport;
 
     private ShapeRenderer shapeRenderer;
+    private SpriteBatch spriteBatch;
+    private SpriteBatch uiSpriteBatch;
 
-    public Graphics(int worldWidth, int worldHeight) {
+    public Graphics() {
-        this.worldWidth = worldWidth;
-        this.worldHeight = worldHeight;
-        this.screenWidth = Gdx.graphics.getWidth();
-        this.screenHeight = Gdx.graphics.getHeight();
-
         this.camera = new OrthographicCamera();
-        this.viewport = new FitViewport(worldWidth, worldHeight, camera);
+        this.uiCamera = new OrthographicCamera();
 
         this.shapeRenderer = new ShapeRenderer();
+        this.spriteBatch = new SpriteBatch();
+        this.uiSpriteBatch = new SpriteBatch();
     }
 
     public void initialize() {
         Gdx.gl.glClearColor(0, 0, 0, 1);
-        updateDimensions();
     }
 
     public void reset() {
         Gdx.gl.glClear(GL20.GL_COLOR_BUFFER_BIT);
     }
 
-    public void setScreenSize(int width, int height) {
-        screenWidth = width;
-        screenHeight = height;
-        updateDimensions();
-    }
-
     public void dispose() {
         shapeRenderer.dispose();
+        spriteBatch.dispose();
+        uiSpriteBatch.dispose();
     }
 
     public ShapeRenderer getShapeRenderer() {
         return shapeRenderer;
     }
 
-    private void updateDimensions() {
+    public SpriteBatch getSpriteBatch() {
-        viewport.setWorldSize(worldWidth, worldHeight);
+        return spriteBatch;
-        viewport.update(screenWidth, screenHeight, true);
+    }
+
+    public SpriteBatch getUISpriteBatch() {
+        return uiSpriteBatch;
+    }
+
+    public void updateViewport(float worldWidth, float worldHeight, float uiWidth, float uiHeight) {
+        camera.setToOrtho(false, worldWidth, worldHeight);
+        uiCamera.setToOrtho(false, uiWidth, uiHeight);
 
         shapeRenderer.setProjectionMatrix(camera.combined);
+        spriteBatch.setProjectionMatrix(camera.combined);
+        uiSpriteBatch.setProjectionMatrix(uiCamera.combined);
     }
 
 }

core/src/com/me/asteroids/components/AccelerationComponent.java

@@ -6,5 +6,48 @@ import com.me.common.ecs.Component;
 public class AccelerationComponent implements Component {
 
     public Vector2 acceleration;
+    public float maxVelocity;
+
+    public AccelerationComponent() {
+        this(0f, 0f, Float.MAX_VALUE);
+    }
+
+    public AccelerationComponent(float maxVelocity) {
+        this(0f, 0f, maxVelocity);
+    }
+
+    public AccelerationComponent(float x, float y, float maxVelocity) {
+        this(new Vector2(x, y), maxVelocity);
+    }
+
+    public AccelerationComponent(Vector2 acceleration, float maxVelocity) {
+        this.acceleration = acceleration;
+        this.maxVelocity = maxVelocity;
+    }
+
+    public float getX() {
+        return acceleration.x;
+    }
+
+    public float getY() {
+        return acceleration.y;
+    }
+
+    public void setX(float x) {
+        acceleration.x = x;
+    }
+
+    public void setY(float y) {
+        acceleration.y = y;
+    }
+
+    public void set(Vector2 vector) {
+        set(vector.x, vector.y);
+    }
+
+    public void set(float x, float y) {
+        acceleration.x = x;
+        acceleration.y = y;
+    }
 
 }

core/src/com/me/asteroids/components/AsteroidComponent.java

@@ -6,4 +6,12 @@ public class AsteroidComponent implements Component {
 
     public int generation;
 
+    public AsteroidComponent() {
+        this(0);
+    }
+
+    public AsteroidComponent(int generation) {
+        this.generation = generation;
+    }
+
 }

core/src/com/me/asteroids/components/BulletTagComponent.java

@@ -2,6 +2,6 @@ package com.me.asteroids.components;
 
 import com.me.common.ecs.Component;
 
-public class BulletComponent implements Component {
+public class BulletTagComponent implements Component {
     // TODO: See PlayerComponent's TODO
 }

core/src/com/me/asteroids/components/ColliderTagComponent.java

@@ -5,5 +5,5 @@ import com.me.common.ecs.Component;
 /**
  * Add this to Entities that should be checked for collisions with other entities.
  */
-public class ColliderComponent implements Component {
+public class ColliderTagComponent implements Component {
 }

core/src/com/me/asteroids/components/DebrisTagComponent.java

@@ -2,6 +2,6 @@ package com.me.asteroids.components;
 
 import com.me.common.ecs.Component;
 
-public class DebrisComponent implements Component {
+public class DebrisTagComponent implements Component {
     // TODO: See PlayerComponent's TODO
 }

core/src/com/me/asteroids/components/GameDataComponent.java

@@ -0,0 +1,28 @@
+package com.me.asteroids.components;
+
+import com.me.asteroids.GameMode;
+import com.me.common.ecs.Component;
+
+public class GameDataComponent implements Component {
+
+    public int score;
+    public int lives;
+    public int newLifeScore;
+
+    public GameMode gameMode;
+    public float gameModeTimer;
+
+    public GameDataComponent() {
+        reset();
+    }
+
+    public void reset() {
+        this.score = 0;
+        this.lives = 3;
+        this.newLifeScore = 0;
+
+        this.gameMode = GameMode.PLAYING;
+        this.gameModeTimer = 0f;
+    }
+
+}

core/src/com/me/asteroids/components/ModelComponent.java

@@ -1,5 +1,9 @@
 package com.me.asteroids.components;
 
+import com.badlogic.gdx.graphics.Color;
+import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
+import com.badlogic.gdx.math.Rectangle;
+import com.badlogic.gdx.math.Vector2;
 import com.me.asteroids.components.model.Model;
 import com.me.common.ecs.Component;
 
@@ -7,4 +11,52 @@ public class ModelComponent implements Component {
 
     public Model model;
 
+    public ModelComponent(Model model) {
+        this.model = model;
+    }
+
+    public Color getColor() {
+        return model.getColor();
+    }
+
+    public ModelComponent setVertices(float[] vertices) {
+        model.setVertices(vertices);
+        return this;
+    }
+
+    public float[] getVertices() {
+        return model.getVertices();
+    }
+
+    public ModelComponent setPosition(Vector2 position) {
+        model.setPosition(position);
+        return this;
+    }
+
+    public Vector2 getPosition() {
+        return model.getPosition();
+    }
+
+    public ModelComponent setRotation(float degrees) {
+        model.setRotation(degrees);
+        return this;
+    }
+
+    public float getRotation() {
+        return model.getRotation();
+    }
+
+    public ModelComponent setScale(float scale) {
+        model.setScale(scale);
+        return this;
+    }
+
+    public float getScale() {
+        return model.getScale();
+    }
+
+    public Rectangle getBoundingBox() {
+        return model.getBoundingBox();
+    }
+
 }

core/src/com/me/asteroids/components/PlayerComponent.java

@@ -1,7 +1,14 @@
 package com.me.asteroids.components;
 
 import com.me.common.ecs.Component;
+import com.me.common.ecs.Entity;
 
 public class PlayerComponent implements Component {
     // TODO: implement engine feature for tagging entities (as player, for e.g.)
+    public Entity afterBurner;
+
+    public PlayerComponent(Entity afterBurner) {
+        this.afterBurner = afterBurner;
+    }
+
 }

core/src/com/me/asteroids/components/PositionComponent.java

@@ -8,4 +8,42 @@ public class PositionComponent implements Component {
     public Vector2 position;
     public float rotation;
 
+    public PositionComponent() {
+        this(0f, 0f, 0f);
+    }
+
+    public PositionComponent(float x, float y, float rotation) {
+        this(new Vector2(x, y), rotation);
+    }
+
+    public PositionComponent(Vector2 position, float rotation) {
+        this.position = position;
+        this.rotation = rotation;
+    }
+
+    public float getX() {
+        return position.x;
+    }
+
+    public float getY() {
+        return position.y;
+    }
+
+    public void setX(float x) {
+        position.x = x;
+    }
+
+    public void setY(float y) {
+        position.y = y;
+    }
+
+    public void set(Vector2 vector) {
+        set(vector.x, vector.y);
+    }
+
+    public void set(float x, float y) {
+        position.x = x;
+        position.y = y;
+    }
+
 }

core/src/com/me/asteroids/components/VelocityComponent.java

@@ -8,6 +8,50 @@ public class VelocityComponent implements Component {
     public Vector2 velocity;
     public float angularVelocity;
 
-    public float maxVelocity = Float.MAX_VALUE;
+    public VelocityComponent() {
+        this(0f, 0f, 0f);
+    }
+
+    public VelocityComponent(Vector2 vector) {
+        this(vector, 0f);
+    }
+
+    public VelocityComponent(float x, float y) {
+        this(x, y, 0f);
+    }
+
+    public VelocityComponent(float x, float y, float angularVelocity) {
+        this(new Vector2(x, y), angularVelocity);
+    }
+
+    public VelocityComponent(Vector2 velocity, float angularVelocity) {
+        this.velocity = velocity;
+        this.angularVelocity = angularVelocity;
+    }
+
+    public float getX() {
+        return velocity.x;
+    }
+
+    public float getY() {
+        return velocity.y;
+    }
+
+    public void setX(float x) {
+        velocity.x = x;
+    }
+
+    public void setY(float y) {
+        velocity.y = y;
+    }
+
+    public void set(Vector2 vector) {
+        set(vector.x, vector.y);
+    }
+
+    public void set(float x, float y) {
+        velocity.x = x;
+        velocity.y = y;
+    }
 
 }

core/src/com/me/asteroids/events/AsteroidHitEvent.java

@@ -0,0 +1,14 @@
+package com.me.asteroids.events;
+
+import com.me.asteroids.components.AsteroidComponent;
+import com.me.common.ecs.event.Event;
+
+public class AsteroidHitEvent extends Event {
+
+    public AsteroidComponent asteroid;
+
+    public AsteroidHitEvent(AsteroidComponent asteroid) {
+        this.asteroid = asteroid;
+    }
+
+}

core/src/com/me/asteroids/events/PlayerDeathEvent.java

@@ -0,0 +1,14 @@
+package com.me.asteroids.events;
+
+import com.me.common.ecs.Entity;
+import com.me.common.ecs.event.Event;
+
+public class PlayerDeathEvent extends Event {
+
+    public Entity player;
+
+    public PlayerDeathEvent(Entity player) {
+        this.player = player;
+    }
+
+}

core/src/com/me/asteroids/screens/GameScreen.java

@@ -10,32 +10,43 @@ import com.me.asteroids.EntityFactory;
 import com.me.asteroids.Graphics;
 import com.me.asteroids.components.AccelerationComponent;
 import com.me.asteroids.components.AsteroidComponent;
-import com.me.asteroids.components.BulletComponent;
+import com.me.asteroids.components.BulletTagComponent;
-import com.me.asteroids.components.ColliderComponent;
+import com.me.asteroids.components.ColliderTagComponent;
-import com.me.asteroids.components.DebrisComponent;
+import com.me.asteroids.components.DebrisTagComponent;
 import com.me.asteroids.components.DecayComponent;
+import com.me.asteroids.components.GameDataComponent;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.PlayerComponent;
 import com.me.asteroids.components.PositionComponent;
 import com.me.asteroids.components.VelocityComponent;
 import com.me.asteroids.components.model.PolygonModel;
+import com.me.asteroids.events.AsteroidHitEvent;
 import com.me.asteroids.events.BulletAsteroidCollisionEvent;
 import com.me.asteroids.events.PlayerASteroidCollisionEvent;
+import com.me.asteroids.events.PlayerDeathEvent;
 import com.me.asteroids.events.ScreenWrapEvent;
 import com.me.asteroids.systems.AsteroidSpawningSystem;
 import com.me.asteroids.systems.CollisionSystem;
 import com.me.asteroids.systems.DecaySystem;
+import com.me.asteroids.systems.GameDataRenderSystem;
+import com.me.asteroids.systems.GameDataSystem;
 import com.me.asteroids.systems.ModelRenderSystem;
 import com.me.asteroids.systems.MovementSystem;
 import com.me.asteroids.systems.PlayerInputSystem;
 import com.me.asteroids.systems.ScreenWrapSystem;
 import com.me.common.Screen;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.event.EventHandler;
 import com.me.common.ecs.event.Listener;
 
+import static com.me.asteroids.Components.ASTEROID;
+import static com.me.asteroids.Components.BULLET;
+import static com.me.asteroids.Components.DEBRIS;
+import static com.me.asteroids.Components.MODEL;
+import static com.me.asteroids.Components.PLAYER;
+import static com.me.asteroids.Components.POSITION;
+
 public class GameScreen extends Screen implements Listener {
 
     Engine engine;
@@ -51,23 +62,27 @@ public class GameScreen extends Screen implements Listener {
 
     @Override
     public void setup() {
-        batch = new SpriteBatch();
+        batch = graphics.getUISpriteBatch();
-        font = new BitmapFont();
+        font = new BitmapFont(Gdx.files.internal("Retro_Font.fnt"));
-        font.setColor(Color.RED);
 
         engine = new Engine();
 
-        engine.registerComponentClass(PlayerComponent.class);
+        engine.registerComponentClass(BulletTagComponent.class);
-        engine.registerComponentClass(BulletComponent.class);
+        engine.registerComponentClass(ColliderTagComponent.class);
+        engine.registerComponentClass(DebrisTagComponent.class);
+
+        engine.registerComponentClass(AccelerationComponent.class);
         engine.registerComponentClass(AsteroidComponent.class);
-        engine.registerComponentClass(DebrisComponent.class);
         engine.registerComponentClass(DecayComponent.class);
-        engine.registerComponentClass(ColliderComponent.class);
+        engine.registerComponentClass(GameDataComponent.class);
+        engine.registerComponentClass(ModelComponent.class);
+        engine.registerComponentClass(PlayerComponent.class);
         engine.registerComponentClass(PositionComponent.class);
         engine.registerComponentClass(VelocityComponent.class);
-        engine.registerComponentClass(AccelerationComponent.class);
-        engine.registerComponentClass(ModelComponent.class);
 
+        GameDataSystem system = new GameDataSystem(engine);
+
+        engine.registerSystem(system);
         engine.registerSystem(new PlayerInputSystem(engine));
         engine.registerSystem(new AsteroidSpawningSystem(engine));
         engine.registerSystem(new DecaySystem(engine));
@@ -75,10 +90,14 @@ public class GameScreen extends Screen implements Listener {
         engine.registerSystem(new CollisionSystem(engine));
         engine.registerSystem(new ScreenWrapSystem(engine));
         engine.registerSystem(new ModelRenderSystem(engine, graphics));
+        engine.registerSystem(new GameDataRenderSystem(engine, graphics, font));
 
-        engine.registerListener(this.new EventListener(engine));
+        engine.registerListener(system);
+        engine.registerListener(this.new EventListener());
 
-        engine.ready();
+        Entity gameData = engine.createEntity();
+        gameData.addComponent(new GameDataComponent());
+        gameData.activate();
 
         Entity player = EntityFactory.createPlayer(engine);
         player.activate();
@@ -91,35 +110,22 @@ public class GameScreen extends Screen implements Listener {
 
         if (Constants.DEBUG) {
             batch.begin();
-            font.draw(batch, String.format("FPS: %d, Entities: %d", Gdx.graphics.getFramesPerSecond(), engine.getEntityCount()), 50, 50);
+            font.setColor(Color.RED);
+            font.draw(batch, String.format("FPS: %d, Entities: %d", Gdx.graphics.getFramesPerSecond(), engine.getEntities().size), 15, 15 + font.getCapHeight());
             batch.end();
         }
     }
 
     @Override
     public void dispose() {
-
+        font.dispose();
     }
 
     private class EventListener implements Listener {
 
-        ComponentMapper<PositionComponent> positionMapper;
-        ComponentMapper<ModelComponent> modelMapper;
-        ComponentMapper<BulletComponent> bulletMapper;
-        ComponentMapper<DebrisComponent> debrisMapper;
-        ComponentMapper<AsteroidComponent> asteroidMapper;
-
-        EventListener(Engine engine) {
-            this.positionMapper = engine.getComponentMapper(PositionComponent.class);
-            this.modelMapper = engine.getComponentMapper(ModelComponent.class);
-            this.bulletMapper = engine.getComponentMapper(BulletComponent.class);
-            this.debrisMapper = engine.getComponentMapper(DebrisComponent.class);
-            this.asteroidMapper = engine.getComponentMapper(AsteroidComponent.class);
-        }
-
         @EventHandler
         public void onScreenWrap(ScreenWrapEvent event) {
-            if (bulletMapper.has(event.entity) || debrisMapper.has(event.entity)) {
+            if (BULLET.has(event.entity) || DEBRIS.has(event.entity)) {
                 // Remove bullets when they leave the screen
                 event.setCancelled(true);
                 event.entity.remove();
@@ -128,15 +134,16 @@ public class GameScreen extends Screen implements Listener {
 
         @EventHandler
         public void onBulletAsteroidCollision(BulletAsteroidCollisionEvent event) {
-            Vector2 bulletPosition = positionMapper.get(event.getBullet()).position;
+            Vector2 bulletPosition = POSITION.get(event.getBullet()).position;
 
-            PolygonModel model = (PolygonModel) modelMapper.get(event.getAsteroid()).model;
+            PolygonModel model = (PolygonModel) MODEL.get(event.getAsteroid()).model;
             if (model.contains(bulletPosition)) {
                 // AABBs intersect but let's only consider it a hit if the bullet's position
                 // is actually inside the asteroid
+                AsteroidComponent asteroid = ASTEROID.get(event.getAsteroid());
+                engine.callEvent(new AsteroidHitEvent(asteroid));
                 event.getBullet().remove();
-                int generation = asteroidMapper.get(event.getAsteroid()).generation;
+                if (asteroid.generation < 2) {
-                if (generation < 2) {
                     for (Entity shard : EntityFactory.splitAsteroidIntoChunks(engine, event.getAsteroid(), 2, 2/3f)) {
                         shard.activate();
                     }
@@ -146,16 +153,17 @@ public class GameScreen extends Screen implements Listener {
                     }
                 }
                 event.getAsteroid().remove();
-
             }
         }
 
         @EventHandler
         public void onPlayerAsteroidCollision(PlayerASteroidCollisionEvent event) {
-            PolygonModel asteroid = (PolygonModel) modelMapper.get(event.getAsteroid()).model;
+            PolygonModel asteroid = (PolygonModel) MODEL.get(event.getAsteroid()).model;
-            PolygonModel player = (PolygonModel) modelMapper.get(event.getPlayer()).model;
+            PolygonModel player = (PolygonModel) MODEL.get(event.getPlayer()).model;
 
             if (asteroid.contains(player.getVertices()) || player.contains(asteroid.getVertices())) {
+                engine.callEvent(new PlayerDeathEvent(event.getPlayer()));
+                PLAYER.get(event.getPlayer()).afterBurner.deactivate();
                 event.getPlayer().deactivate();
                 for (Entity debris : EntityFactory.createDebris(engine, event.getPlayer())) {
                     debris.activate();

core/src/com/me/asteroids/systems/AsteroidSpawningSystem.java

@@ -2,37 +2,26 @@ package com.me.asteroids.systems;
 
 import com.badlogic.gdx.math.Rectangle;
 import com.badlogic.gdx.math.Vector2;
-import com.badlogic.gdx.utils.Array;
 import com.me.asteroids.Constants;
 import com.me.asteroids.EntityFactory;
 import com.me.asteroids.Utils;
-import com.me.asteroids.components.AsteroidComponent;
-import com.me.asteroids.components.ModelComponent;
-import com.me.asteroids.components.PositionComponent;
 import com.me.asteroids.components.VelocityComponent;
 import com.me.asteroids.components.model.Model;
 import com.me.common.ecs.BaseSystem;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 
+import static com.me.asteroids.Components.MODEL;
+import static com.me.asteroids.Components.POSITION;
+import static com.me.asteroids.Components.VELOCITY;
 import static com.me.asteroids.Constants.rand;
 
 public class AsteroidSpawningSystem extends BaseSystem {
 
-    private ComponentMapper<AsteroidComponent> asteroidMapper;
-    private ComponentMapper<PositionComponent> positionMapper;
-    private ComponentMapper<VelocityComponent> velocityMapper;
-    private ComponentMapper<ModelComponent> modelMapper;
-
     private float asteroidSpawnDelay = 0f;
 
     public AsteroidSpawningSystem(Engine engine) {
         super(engine);
-        asteroidMapper = engine.getComponentMapper(AsteroidComponent.class);
-        positionMapper = engine.getComponentMapper(PositionComponent.class);
-        velocityMapper = engine.getComponentMapper(VelocityComponent.class);
-        modelMapper = engine.getComponentMapper(ModelComponent.class);
     }
 
     private Vector2 getRandomSpawnLocation(float asteroidWidth, float asteroidHeight) {
@@ -55,16 +44,16 @@ public class AsteroidSpawningSystem extends BaseSystem {
     private void spawnAsteroid() {
         Entity asteroid = EntityFactory.createAsteroid(engine);
 
-        Model model = modelMapper.get(asteroid).model;
+        Model model = MODEL.get(asteroid).model;
         Rectangle aabb = model.getBoundingBox();
 
         Vector2 position
-                = positionMapper.get(asteroid).position
+                = POSITION.get(asteroid).position
                 = getRandomSpawnLocation(aabb.getWidth(), aabb.getHeight());
         model.setPosition(position);
 
-        VelocityComponent velocityComponent = velocityMapper.get(asteroid);
+        VelocityComponent velocityComponent = VELOCITY.get(asteroid);
-        velocityComponent.velocity = new Vector2().setToRandomDirection().scl(rand.nextFloat(75, 125));
+        velocityComponent.velocity = new Vector2().setToRandomDirection().scl(rand.nextFloat(1.875f, 3.125f));
         velocityComponent.angularVelocity = rand.nextFloat(-30, 30);
 
         asteroid.activate();
@@ -72,16 +61,7 @@ public class AsteroidSpawningSystem extends BaseSystem {
 
     @Override
     public void process(float dt) {
-        Array<Entity> entities = engine.getEntities();
+        int asteroidCount = engine.getEntitiesInGroup("ASTEROIDS").size;
-        int asteroidCount = 0;
-        for (Entity entity : entities) {
-            // It's rather inefficient to have to check our entire entity list every frame
-            // to count how many entities have a specific component. Maybe we should keep a count of
-            // how many entites a given component?
-            if (asteroidMapper.has(entity)) {
-                asteroidCount++;
-            }
-        }
 
         if (asteroidCount++ < Constants.ASTEROID_SPAWN_COUNT && (asteroidSpawnDelay -= dt) <= 0) {
             spawnAsteroid();

core/src/com/me/asteroids/systems/CollisionSystem.java

@@ -2,20 +2,18 @@ package com.me.asteroids.systems;
 
 import com.badlogic.gdx.math.Rectangle;
 import com.me.asteroids.EventFactory;
-import com.me.asteroids.components.ColliderComponent;
+import com.me.asteroids.components.ColliderTagComponent;
 import com.me.asteroids.components.ModelComponent;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.EntitySystem;
 
+import static com.me.asteroids.Components.MODEL;
+
 public class CollisionSystem extends EntitySystem {
 
-    private ComponentMapper<ModelComponent> modelMapper;
-
     public CollisionSystem(Engine engine) {
-        super(engine, ColliderComponent.class, ModelComponent.class);
+        super(engine, ColliderTagComponent.class, ModelComponent.class);
-        modelMapper = engine.getComponentMapper(ModelComponent.class);
     }
 
     @Override
@@ -23,19 +21,18 @@ public class CollisionSystem extends EntitySystem {
         Entity[] entities = getEntities().items;
         for (int i = 0, n = getEntities().size; i < n-1; i++) {
             Entity entityA = entities[i];
-            if (!entityA.isActive() || entityA.isRemoved()) {
+            if (!entityA.isActive()) {
                 continue;
             }
 
-            Rectangle aabbA = modelMapper.get(entityA).model.getBoundingBox();
+            Rectangle aabbA = MODEL.get(entityA).model.getBoundingBox();
-
             for (int j = i + 1; j < n; j++) {
                 Entity entityB = entities[j];
-                if (!entityB.isActive() || entityB.isRemoved()) {
+                if (!entityB.isActive()) {
                     continue;
                 }
 
-                Rectangle aabbB = modelMapper.get(entityB).model.getBoundingBox();
+                Rectangle aabbB = MODEL.get(entityB).model.getBoundingBox();
                 if (aabbA.overlaps(aabbB)) {
                     engine.callEvent(EventFactory.getNewCollisionEvent(entityA, entityB));
                 }

core/src/com/me/asteroids/systems/DecaySystem.java

@@ -1,30 +1,27 @@
 package com.me.asteroids.systems;
 
 import com.me.asteroids.components.DecayComponent;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.EntitySystem;
 
-public class DecaySystem extends EntitySystem {
+import static com.me.asteroids.Components.DECAY;
 
-    private ComponentMapper<DecayComponent> decayTimerMapper;
+public class DecaySystem extends EntitySystem {
 
     public DecaySystem(Engine engine) {
         super(engine, DecayComponent.class);
-        decayTimerMapper = engine.getComponentMapper(DecayComponent.class);
     }
 
     @Override
     public void processEntity(Entity entity, float dt) {
-        DecayComponent decayComponent = decayTimerMapper.get(entity);
+        DecayComponent decayComponent = DECAY.get(entity);
         if ((decayComponent.decayTimer -= dt) <= 0) {
             if (decayComponent.remove) {
                 entity.remove();
             } else {
                 entity.deactivate();
             }
-
         }
     }
 

core/src/com/me/asteroids/systems/GameDataRenderSystem.java

@@ -0,0 +1,60 @@
+package com.me.asteroids.systems;
+
+import com.badlogic.gdx.graphics.Color;
+import com.badlogic.gdx.graphics.g2d.BitmapFont;
+import com.badlogic.gdx.graphics.g2d.GlyphLayout;
+import com.badlogic.gdx.graphics.g2d.SpriteBatch;
+import com.me.asteroids.Constants;
+import com.me.asteroids.Graphics;
+import com.me.asteroids.components.GameDataComponent;
+import com.me.common.ecs.Engine;
+import com.me.common.ecs.Entity;
+import com.me.common.ecs.EntitySystem;
+
+import static com.me.asteroids.Components.GAME_DATA;
+
+public class GameDataRenderSystem extends EntitySystem {
+
+    private SpriteBatch batch;
+    private BitmapFont font;
+    private GlyphLayout gameOverLayout;
+
+    private GameDataComponent gameData;
+
+    public GameDataRenderSystem(Engine engine, Graphics graphics, BitmapFont font) {
+        super(engine, GameDataComponent.class);
+        this.batch = graphics.getUISpriteBatch();
+        this.font = font;
+        this.gameOverLayout = new GlyphLayout(font, "GAME OVER");
+    }
+
+    @Override
+    public void preProcess() {
+        batch.begin();
+    }
+
+    @Override
+    public void processEntity(Entity entity, float dt) {
+        if(gameData == null) {
+            gameData = GAME_DATA.get(entity);
+        }
+
+        switch (gameData.gameMode) {
+            case GAME_OVER:
+                font.setColor(Color.RED);
+                font.draw(batch, "GAME OVER", Constants.getHalfUIWidth() - (gameOverLayout.width / 2), Constants.getHalfUIHeight() + (font.getCapHeight() / 2));
+                break;
+            default:
+                font.setColor(Color.CHARTREUSE);
+                font.draw(batch, "Score: " + gameData.score, 15, Constants.getUIHeight() - 15);
+                font.draw(batch, "Lives: " + gameData.lives, 15, Constants.getUIHeight() - font.getCapHeight() - 30);
+                break;
+        }
+    }
+
+    @Override
+    public void postProcess() {
+        batch.end();
+    }
+
+}

core/src/com/me/asteroids/systems/GameDataSystem.java

@@ -0,0 +1,101 @@
+package com.me.asteroids.systems;
+
+import com.me.asteroids.Constants;
+import com.me.asteroids.GameMode;
+import com.me.asteroids.components.GameDataComponent;
+import com.me.asteroids.components.PositionComponent;
+import com.me.asteroids.events.AsteroidHitEvent;
+import com.me.asteroids.events.PlayerDeathEvent;
+import com.me.common.ecs.Engine;
+import com.me.common.ecs.Entity;
+import com.me.common.ecs.EntitySystem;
+import com.me.common.ecs.event.EventHandler;
+import com.me.common.ecs.event.Listener;
+
+import static com.me.asteroids.Components.GAME_DATA;
+import static com.me.asteroids.Components.POSITION;
+import static com.me.asteroids.Components.VELOCITY;
+
+public class GameDataSystem extends EntitySystem implements Listener {
+
+    private GameDataComponent gameData;
+
+    public GameDataSystem(Engine engine) {
+        super(engine, GameDataComponent.class);
+    }
+
+    @Override
+    public void processEntity(Entity entity, float dt) {
+        if(gameData == null) {
+            gameData = GAME_DATA.get(entity);
+        }
+
+        if (gameData.gameModeTimer > 0 && (gameData.gameModeTimer -= dt) < 0) {
+            switch (gameData.gameMode) {
+                case DIED:
+                    if (--gameData.lives >= 0) {
+                        resetPlayer();
+                        setGameMode(GameMode.PLAYING);
+                    } else {
+                        setGameMode(GameMode.GAME_OVER);
+                    }
+                    break;
+                case GAME_OVER:
+                    gameData.reset();
+                    resetPlayer();
+                    setGameMode(GameMode.PLAYING);
+            }
+        }
+    }
+
+    @EventHandler
+    public void onAsteroidHit(AsteroidHitEvent event) {
+        if (gameData == null) {
+            return;
+        }
+
+        switch (event.asteroid.generation) {
+            case 0:
+                gameData.score += 20;
+                gameData.newLifeScore += 20;
+                break;
+            case 1:
+                gameData.score += 50;
+                gameData.newLifeScore += 50;
+                break;
+            default:
+                gameData.score += 100;
+                gameData.newLifeScore += 100;
+        }
+
+        if (gameData.newLifeScore >= Constants.NEW_LIFE_SCORE) {
+            gameData.newLifeScore -= Constants.NEW_LIFE_SCORE;
+            gameData.lives++;
+        }
+    }
+
+
+    @EventHandler
+    public void onPlayerDeath(PlayerDeathEvent event) {
+        if (gameData == null) {
+            return;
+        }
+
+        setGameMode(GameMode.DIED);
+    }
+
+    private void resetPlayer() {
+        Entity player = engine.getEntityByTag("PLAYER");
+        PositionComponent position = POSITION.get(player);
+        position.set(Constants.HALF_WIDTH, Constants.HALF_HEIGHT);
+        position.rotation = 90;
+        VELOCITY.get(player).set(0, 0);
+        player.activate();
+    }
+
+    private void setGameMode(GameMode mode) {
+        gameData.gameMode = mode;
+        gameData.gameModeTimer = mode.getTimer();
+    }
+
+}

core/src/com/me/asteroids/systems/ModelRenderSystem.java

@@ -4,20 +4,18 @@ import com.badlogic.gdx.graphics.glutils.ShapeRenderer;
 import com.me.asteroids.Graphics;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.model.Model;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.EntitySystem;
 
-public class ModelRenderSystem extends EntitySystem {
+import static com.me.asteroids.Components.MODEL;
 
-    private ComponentMapper<ModelComponent> modelMapper;
+public class ModelRenderSystem extends EntitySystem {
 
     private ShapeRenderer renderer;
 
     public ModelRenderSystem(Engine engine, Graphics graphics) {
         super(engine, ModelComponent.class);
-        this.modelMapper = engine.getComponentMapper(ModelComponent.class);
         this.renderer = graphics.getShapeRenderer();
     }
 
@@ -28,7 +26,7 @@ public class ModelRenderSystem extends EntitySystem {
 
     @Override
     public void processEntity(Entity entity, float dt) {
-        Model model = modelMapper.get(entity).model;
+        Model model = MODEL.get(entity).model;
 
         renderer.setColor(model.getColor());
         model.render(renderer);

core/src/com/me/asteroids/systems/MovementSystem.java

@@ -8,46 +8,50 @@ import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.PositionComponent;
 import com.me.asteroids.components.VelocityComponent;
 import com.me.asteroids.components.model.Model;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.EntitySystem;
 
+import static com.me.asteroids.Components.ACCELERATION;
+import static com.me.asteroids.Components.MODEL;
+import static com.me.asteroids.Components.POSITION;
+import static com.me.asteroids.Components.VELOCITY;
+
 public class MovementSystem extends EntitySystem {
 
     private Vector2 tmp = new Vector2();
 
-    private ComponentMapper<PositionComponent> positionMapper;
-    private ComponentMapper<VelocityComponent> velocityMapper;
-    private ComponentMapper<AccelerationComponent> accelMapper;
-    private ComponentMapper<ModelComponent> modelMapper;
-
     public MovementSystem(Engine engine) {
         super(engine, PositionComponent.class, VelocityComponent.class);
-
-        positionMapper = engine.getComponentMapper(PositionComponent.class);
-        velocityMapper = engine.getComponentMapper(VelocityComponent.class);
-        accelMapper = engine.getComponentMapper(AccelerationComponent.class);
-        modelMapper = engine.getComponentMapper(ModelComponent.class);
     }
 
     @Override
     public void processEntity(Entity entity, float dt) {
-        PositionComponent positionComponent = positionMapper.get(entity);
+        PositionComponent positionComponent = POSITION.get(entity);
-        VelocityComponent velocityComponent = velocityMapper.get(entity);
+        VelocityComponent velocityComponent = VELOCITY.get(entity);
+        AccelerationComponent accelComponent = ACCELERATION.get(entity);
 
         Vector2 velocity = velocityComponent.velocity;
 
-        AccelerationComponent accelComponent = accelMapper.get(entity);
         if (accelComponent != null && !accelComponent.acceleration.isZero()) {
-            velocity.add(tmp.set(accelComponent.acceleration).scl(dt));
+            tmp.set(accelComponent.acceleration).scl(dt).add(velocity);
+
+            if (velocity.dot(tmp) < 0) {
+                // current velocity is opposite of velocity with acceleration applied, which means
+                // we're coming to a stop. Set position correctly and velocity to zero
+                velocity.set(0, 0);
+                positionComponent.position.add(tmp.scl(dt));
+            } else {
+                // Else just use the accelerated velocity
+                velocity.set(tmp);
+                velocity.clamp(0, accelComponent.maxVelocity);
+            }
         }
 
-        float maxVelocity = velocityComponent.maxVelocity;
         Vector2 position = positionComponent.position;
+
         if (!velocity.isZero()) {
-            velocity.clamp(0, maxVelocity);
+            positionComponent.position.add(tmp.set(velocity).scl(dt));
-            position.add(tmp.set(velocity).scl(dt));
         }
 
         float angularVelocity = velocityComponent.angularVelocity;
@@ -55,7 +59,7 @@ public class MovementSystem extends EntitySystem {
             positionComponent.rotation = Utils.wrapAngle(positionComponent.rotation + (angularVelocity * dt));
         }
 
-        ModelComponent modelComponent = modelMapper.get(entity);
+        ModelComponent modelComponent = MODEL.get(entity);
         if (modelComponent != null) {
             Model model = modelComponent.model;
             model.setPosition(position);

core/src/com/me/asteroids/systems/PlayerInputSystem.java

@@ -9,19 +9,21 @@ import com.me.asteroids.components.AccelerationComponent;
 import com.me.asteroids.components.PlayerComponent;
 import com.me.asteroids.components.PositionComponent;
 import com.me.asteroids.components.VelocityComponent;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.EntitySystem;
 
+import static com.me.asteroids.Constants.rand;
+import static com.me.asteroids.Components.ACCELERATION;
+import static com.me.asteroids.Components.MODEL;
+import static com.me.asteroids.Components.PLAYER;
+import static com.me.asteroids.Components.POSITION;
+import static com.me.asteroids.Components.VELOCITY;
+
 public class PlayerInputSystem extends EntitySystem {
 
     public Vector2 tmp = new Vector2(0, 1);
 
-    private ComponentMapper<PositionComponent> positionMapper;
-    private ComponentMapper<VelocityComponent> velocityMapper;
-    private ComponentMapper<AccelerationComponent> accelMapper;
-
     public PlayerInputSystem(Engine engine) {
         super(
                 engine,
@@ -30,16 +32,14 @@ public class PlayerInputSystem extends EntitySystem {
                 AccelerationComponent.class,
                 PlayerComponent.class
         );
-        positionMapper = engine.getComponentMapper(PositionComponent.class);
-        velocityMapper = engine.getComponentMapper(VelocityComponent.class);
-        accelMapper = engine.getComponentMapper(AccelerationComponent.class);
     }
 
     @Override
     public void processEntity(Entity entity, float dt) {
-        PositionComponent positionComponent = positionMapper.get(entity);
+        PositionComponent positionComponent = POSITION.get(entity);
-        VelocityComponent velocityComponent = velocityMapper.get(entity);
+        VelocityComponent velocityComponent = VELOCITY.get(entity);
-        AccelerationComponent accelComponent = accelMapper.get(entity);
+        AccelerationComponent accelComponent = ACCELERATION.get(entity);
+        PlayerComponent playerComponent = PLAYER.get(entity);
 
         boolean isLeftPressed = Gdx.input.isKeyPressed(Input.Keys.A);
         boolean isRightPressed = Gdx.input.isKeyPressed(Input.Keys.D);
@@ -51,16 +51,27 @@ public class PlayerInputSystem extends EntitySystem {
             velocityComponent.angularVelocity = 0;
         }
 
-        Vector2 acceleration = accelComponent.acceleration;
         Vector2 velocity = velocityComponent.velocity;
 
+        MODEL.get(playerComponent.afterBurner).setPosition(positionComponent.position);
+
         if (Gdx.input.isKeyPressed(Input.Keys.W)) {
-            acceleration.set(Utils.setUnitVectorAngle(tmp, positionComponent.rotation).scl(500));
+            accelComponent.set(Utils.setUnitVectorAngle(tmp, positionComponent.rotation).scl(12.5f));
-        } else {
+
-            if (!velocity.isZero(1f)) {
+            if (rand.nextFloat() < 0.85) {
-                acceleration.set(Utils.setUnitVectorAngleRad(tmp, velocity.angleRad()).scl(-100));
+                PositionComponent afterBurnerPosition = POSITION.get(playerComponent.afterBurner);
+                afterBurnerPosition.position.set(positionComponent.position);
+                afterBurnerPosition.rotation = positionComponent.rotation;
+                playerComponent.afterBurner.activate();
             } else {
-                acceleration.set(0, 0);
+                playerComponent.afterBurner.deactivate();
+            }
+        } else {
+            playerComponent.afterBurner.deactivate();
+            if (velocity.isZero(0f)) {
+                accelComponent.set(0, 0);
+            } else {
+                accelComponent.set(Utils.setUnitVectorAngleRad(tmp, velocity.angleRad()).scl(-2.5f));
             }
         }
 

core/src/com/me/asteroids/systems/ScreenWrapSystem.java

@@ -6,20 +6,17 @@ import com.me.asteroids.Constants;
 import com.me.asteroids.components.ModelComponent;
 import com.me.asteroids.components.PositionComponent;
 import com.me.asteroids.events.ScreenWrapEvent;
-import com.me.common.ecs.ComponentMapper;
 import com.me.common.ecs.Engine;
 import com.me.common.ecs.Entity;
 import com.me.common.ecs.EntitySystem;
 
-public class ScreenWrapSystem extends EntitySystem {
+import static com.me.asteroids.Components.MODEL;
+import static com.me.asteroids.Components.POSITION;
 
-    private ComponentMapper<PositionComponent> positionMapper;
+public class ScreenWrapSystem extends EntitySystem {
-    private ComponentMapper<ModelComponent> modelMapper;
 
     public ScreenWrapSystem(Engine engine) {
         super(engine, PositionComponent.class, ModelComponent.class);
-        positionMapper = engine.getComponentMapper(PositionComponent.class);
-        modelMapper = engine.getComponentMapper(ModelComponent.class);
     }
 
     private void updatePosition(Entity entity, Vector2 position, float newX, float newY) {
@@ -33,8 +30,8 @@ public class ScreenWrapSystem extends EntitySystem {
 
     @Override
     public void processEntity(Entity entity, float dt) {
-        Vector2 position = positionMapper.get(entity).position;
+        Vector2 position = POSITION.get(entity).position;
-        Rectangle aabb = modelMapper.get(entity).model.getBoundingBox();
+        Rectangle aabb = MODEL.get(entity).model.getBoundingBox();
 
         // Check top/bottom edges
         float minY = aabb.y;

core/src/com/me/common/ecs/BaseSystem.java

@@ -2,7 +2,7 @@ package com.me.common.ecs;
 
 public abstract class BaseSystem {
 
-    protected Engine engine;
+    protected final Engine engine;
 
     public BaseSystem(Engine engine) {
         this.engine = engine;

core/src/com/me/common/ecs/ComponentBag.java

@@ -1,38 +1,33 @@
 package com.me.common.ecs;
 
-public class ComponentBag {
+class ComponentBag {
 
     private Component[] items;
     private int size;
 
-    public ComponentBag() {
+    ComponentBag() {
         this.items = new Component[16];
         this.size = items.length;
     }
 
-    public Component get(int index) {
+    Component get(int index) {
         if (index >= size) {
             return null;
         }
         return items[index];
     }
 
-    public boolean contains(int index) {
+    void insert(int index, Component item) {
-        return index < size && items[index] != null;
-    }
-
-    public void insert(int index, Component item) {
         if (index >= size) {
             grow((int) (index * 1.5f));
         }
         items[index] = item;
     }
 
-    public void remove(int index) {
+    void remove(int index) {
-        if (index >= size) {
+        if (index < size) {
-            throw new IndexOutOfBoundsException("index must be < size");
+            items[index] = null;
         }
-        items[index] = null;
     }
 
     private void grow(int newSize) {

core/src/com/me/common/ecs/ComponentMapper.java

@@ -1,23 +1,36 @@
 package com.me.common.ecs;
 
-public class ComponentMapper<T extends Component> {
+import java.util.HashMap;
+import java.util.Map;
 
-    private Engine engine;
+public final class ComponentMapper<T extends Component> {
-    private ComponentType type;
-    private Class<T> typeClass;
 
-    public ComponentMapper(Engine engine, Class<T> typeClass) {
+    private static final Map<Class<? extends Component>, ComponentMapper> mappers = new HashMap<>();
-        this.engine = engine;
+
+    private final ComponentType type;
+    private final Class<T> typeClass;
+
+    private ComponentMapper(Class<T> typeClass) {
         this.type = ComponentType.getComponentType(typeClass);
         this.typeClass = typeClass;
     }
 
     public T get(Entity entity) {
-        return typeClass.cast(engine.getEntityComponent(entity, type));
+        return typeClass.cast(entity.getComponent(type));
     }
 
     public boolean has(Entity entity) {
-        return type.isTypeInMask(entity.componentBits);
+        return type.isInBits(entity.componentBits);
+    }
+
+    @SuppressWarnings("unchecked")
+    public static <T extends Component> ComponentMapper<T> getFor(Class<T> typeClass) {
+        ComponentMapper<T> mapper = mappers.get(typeClass);
+        if (mapper == null) {
+            mapper = new ComponentMapper<>(typeClass);
+            mappers.put(typeClass, mapper);
+        }
+        return mapper;
     }
 
 }

core/src/com/me/common/ecs/ComponentType.java

@@ -6,64 +6,44 @@ import java.util.Map;
 final class ComponentType {
 
     private static final Map<Class<? extends Component>, ComponentType> types = new HashMap<>();
-    private static final ComponentType[] typeById = new ComponentType[Long.SIZE];
 
     private static long nextBit = 1l;
     private static int nextId = 0;
 
-    protected long bits;
+    final long bit;
-    protected int id;
+    final int id;
 
     private ComponentType() {
-        this.bits = nextBit;
+        this.bit = nextBit;
         this.id = nextId++;
 
-        this.nextBit <<= 1;
+        nextBit <<= 1;
     }
 
-    protected long getBits() {
+    boolean isInBits(long bits) {
+        return (bits & bit) == bit;
+    }
+
+    @SafeVarargs
+    static long getBitsFor(Class<? extends Component>... components) {
+        long bits = 0l;
+        for (Class<? extends Component> clazz : components) {
+            bits |= getComponentType(clazz).bit;
+        }
         return bits;
     }
 
-    protected int getId() {
+    static ComponentType registerComponentType(Class<? extends Component> component) {
-        return id;
-    }
-
-    protected static long getMaskBits(Class<? extends Component>... components) {
-        long mask = 0l;
-        for (Class<? extends Component> clazz : components) {
-            mask |= getTypeBits(clazz);
-        }
-        return mask;
-    }
-
-    protected static long getTypeBits(Class<? extends Component> component) {
-        return getComponentType(component).bits;
-    }
-
-    protected static int getTypeId(Class<? extends Component> component) {
-        return getComponentType(component).id;
-    }
-
-    protected static ComponentType getById(int id) {
-        return typeById[id];
-    }
-
-    protected boolean isTypeInMask(long mask) {
-        return (bits & mask) == bits;
-    }
-
-    protected static void registerComponentType(Class<? extends Component> component) {
         ComponentType type = types.get(component);
         if (type != null) {
             throw new IllegalArgumentException(component.getName() + " has already been registered.");
         }
         type = new ComponentType();
         types.put(component, type);
-        typeById[type.id] = type;
+        return type;
     }
 
-    protected static ComponentType getComponentType(Class<? extends Component> component) {
+    static ComponentType getComponentType(Class<? extends Component> component) {
         ComponentType type = types.get(component);
         if (type == null) {
             throw new IllegalArgumentException(component.getName() + " has not been registered.");
@@ -71,8 +51,4 @@ final class ComponentType {
         return type;
     }
 
-    protected static int getRegisteredComponentTypeCount() {
-        return types.size();
-    }
-
 }

core/src/com/me/common/ecs/Engine.java

@@ -1,49 +1,55 @@
 package com.me.common.ecs;
 
 import com.badlogic.gdx.utils.Array;
+import com.badlogic.gdx.utils.ObjectSet;
 import com.me.common.ecs.event.Event;
 import com.me.common.ecs.event.Listener;
 
-import java.util.HashMap;
-import java.util.Map;
-
 public class Engine {
 
-    private ComponentBag[] components;
+    private final EntityManager entityManager;
-    protected Array<BaseSystem> systems;
+    private final ComponentBag[] components;
+    private final Array<BaseSystem> systems;
 
-    private EntityManager entityManager;
+    private final ListenerRegistry listenerRegistry;
-    private ListenerRegistry listenerRegistry;
-
-    private Map<Class<? extends Component>, ComponentMapper> componentMappers;
 
     public Engine() {
         this.entityManager = new EntityManager(this);
-
+        this.components = new ComponentBag[Long.SIZE];
         this.systems = new Array<>();
+
         this.listenerRegistry = new ListenerRegistry();
-        this.componentMappers = new HashMap<>();
     }
 
+    /**
+     * Register a Component class.
+     * @param clazz
+     */
     public void registerComponentClass(Class<? extends Component> clazz) {
-        ComponentType.registerComponentType(clazz);
+        ComponentType type = ComponentType.registerComponentType(clazz);
+        components[type.id] = new ComponentBag();
     }
 
+    /**
+     * Register a BaseSystem.
+     * @param system
+     */
     public void registerSystem(BaseSystem system) {
-        this.systems.add(system);
+        systems.add(system);
     }
 
+    /**
+     * Register an event Listener.
+     * @param listener
+     */
     public void registerListener(Listener listener) {
         listenerRegistry.registerListener(listener);
     }
 
-    public void ready() {
+    /**
-        this.components = new ComponentBag[ComponentType.getRegisteredComponentTypeCount()];
+     * Process all systems
-        for (int i = 0; i < components.length; i++) {
+     * @param dt the time (in seconds) passed since the last update
-            components[i] = new ComponentBag();
+     */
-        }
-    }
-
     public void update(float dt) {
         entityManager.update();
 
@@ -54,61 +60,103 @@ public class Engine {
         }
     }
 
+    /**
+     * @return all entities known by the engine - both those active and inactive.
+     */
     public Array<Entity> getEntities() {
-        return entityManager.entities;
+        return entityManager.getEntities();
     }
 
-    public int getEntityCount() {
+    /**
-        return entityManager.entities.size;
+     * @return all currently registered systems.
+     */
+    public Array<BaseSystem> getSystems() {
+        return systems;
     }
 
+    /**
+     * @return a new Entity object which can have fresh components added to it
+     */
     public Entity createEntity() {
         return entityManager.create();
     }
 
+    /**
+     * Calls the given event, dispatching it to all registered Listeners that have an EventHandler
+     * for this particular event.
+     * @param event the event to call
+     */
     public void callEvent(Event event) {
         listenerRegistry.callEvent(event);
     }
 
-    protected void refreshEntity(Entity entity) {
+    /**
+     * @param group the group to look up
+     * @return the list of entities that are a part of the given group.
+     */
+    public Array<Entity> getEntitiesInGroup(String group) {
+        return entityManager.getGroupEntities(group);
+    }
+
+    /**
+     * @param tag the tag to look up
+     * @return the entity with the given tag, or null
+     */
+    public Entity getEntityByTag(String tag) {
+        return entityManager.getEntityByTag(tag);
+    }
+
+
+    void addEntityGroup(Entity entity, String group) {
+        entityManager.addEntityToGroup(entity, group);
+    }
+
+    void removeEntityGroup(Entity entity, String group) {
+        entityManager.removeEntityFromGroup(entity, group);
+    }
+
+    void tagEntity(Entity entity, String tag) {
+        entityManager.tagEntity(entity, tag);
+    }
+
+    void removeEntityTag(Entity entity) {
+        entityManager.removeEntityTag(entity);
+    }
+
+    void refreshEntity(Entity entity) {
         entityManager.queueRefresh(entity);
     }
 
-    protected void removeAllEntityComponents(int entityId) {
+    void removeAllEntityComponents(int entityId) {
-        for (int i = 0; i < components.length; i++) {
+        for (ComponentBag bag : components) {
-            components[i].insert(entityId, null);
+            if (bag == null) {
+                // The rest of the array should also be null given that we never nullify
+                // an index after it has been set, and they are set sequentially. So, break.
+                break;
+            }
+            bag.remove(entityId);
         }
     }
 
-    protected void addEntityComponent(Entity entity, Component component) {
+    void addEntityComponent(Entity entity, Component component) {
         ComponentType type = ComponentType.getComponentType(component.getClass());
         components[type.id].insert(entity.id, component);
         entity.addComponentType(type);
     }
 
 
-    protected void removeEntityComponent(Entity entity, Component component) {
+    void removeEntityComponent(Entity entity, Component component) {
         ComponentType type = ComponentType.getComponentType(component.getClass());
         components[type.id].remove(entity.id);
         entity.removeComponentType(type);
     }
 
-    protected <T extends Component> T getEntityComponent(Entity entity, Class<T> clazz) {
+    <T extends Component> T getEntityComponent(Entity entity, Class<T> clazz) {
-        return clazz.cast(components[ComponentType.getTypeId(clazz)].get(entity.id));
+        return clazz.cast(getEntityComponent(entity, ComponentType.getComponentType(clazz)));
     }
 
-    protected Component getEntityComponent(Entity entity, ComponentType type) {
+    Component getEntityComponent(Entity entity, ComponentType type) {
         return components[type.id].get(entity.id);
     }
 
-    @SuppressWarnings("unchecked")
-    public <T extends Component> ComponentMapper<T> getComponentMapper(Class<T> typeClass) {
-        ComponentMapper<T> mapper = componentMappers.get(typeClass);
-        if (mapper == null) {
-            mapper = new ComponentMapper<>(this, typeClass);
-            componentMappers.put(typeClass, mapper);
-        }
-        return mapper;
-    }
-
 }

core/src/com/me/common/ecs/Entity.java

@@ -1,25 +1,31 @@
 package com.me.common.ecs;
 
+import com.badlogic.gdx.utils.ObjectSet;
+
 public final class Entity {
 
     private static int nextId = 0;
     private static long nextUniqueId = 0;
 
-    private Engine engine;
+    private final Engine engine;
-    protected final int id;
+    final int id;
 
-    protected long componentBits;
+    long componentBits;
-    protected long systemEnabledBits;
+    long systemEnabledBits;
+    boolean pendingRefresh;
 
-    protected boolean active;
+    boolean active;
-    protected boolean removed;
+    boolean removed;
-    protected boolean pendingRefresh;
+
+    ObjectSet<String> groups;
+    String tag;
 
     private long uniqueId;
 
     protected Entity(Engine engine) {
         this.engine = engine;
         this.id = nextId++;
+        this.groups = new ObjectSet<>();
     }
 
     public int getId() {
@@ -30,6 +36,10 @@ public final class Entity {
         return uniqueId;
     }
 
+    public Engine getEngine() {
+        return engine;
+    }
+
     public boolean isActive() {
         return active;
     }
@@ -39,30 +49,25 @@ public final class Entity {
     }
 
     public void activate() {
-        active = true;
+        if (!active) {
-        refresh();
+            active = true;
+            refresh();
+        }
     }
 
     public void deactivate() {
-        active = false;
+        if (active) {
-        refresh();
+            active = false;
+            refresh();
+        }
     }
 
     public void remove() {
-        removed = true;
+        if (!removed) {
-        refresh();
+            removed = true;
-    }
+            active = false;
-
+            refresh();
-    public Engine getEngine() {
+        }
-        return this.engine;
-    }
-
-    public boolean hasComponent(Class<? extends Component> clazz) {
-        return ComponentType.getComponentType(clazz).isTypeInMask(componentBits);
-    }
-
-    public <T extends Component> T getComponent(Class<T> clazz) {
-        return engine.getEntityComponent(this, clazz);
     }
 
     public void addComponent(Component component) {
@@ -75,39 +80,81 @@ public final class Entity {
         refresh();
     }
 
-    protected void addComponentType(ComponentType type) {
+    private void refresh() {
-        componentBits |= type.bits;
-    }
-
-    protected void removeComponentType(ComponentType type) {
-        componentBits &= ~type.bits;
-    }
-
-    protected void addSystemEnabledBit(long bit) {
-        systemEnabledBits |= bit;
-    }
-
-    protected void removeSystemEnabledBit(long bit) {
-        systemEnabledBits &= ~bit;
-    }
-
-    public void refresh() {
         if (!pendingRefresh) {
             engine.refreshEntity(this);
             pendingRefresh = true;
         }
     }
 
-    protected void reset() {
+    public boolean hasComponent(Class<? extends Component> clazz) {
+        return ComponentType.getComponentType(clazz).isInBits(componentBits);
+    }
+
+    public <T extends Component> T getComponent(Class<T> clazz) {
+        return engine.getEntityComponent(this, clazz);
+    }
+
+    public ObjectSet<String> getGroups() {
+        return groups;
+    }
+
+    public void addGroup(String group) {
+        engine.addEntityGroup(this, group);
+    }
+
+    public void removeGroup(String group) {
+        engine.removeEntityGroup(this, group);
+    }
+
+    public boolean inGroup(String group) {
+        return groups.contains(group);
+    }
+
+    public String getTag() {
+        return tag;
+    }
+
+    public void setTag(String tag) {
+        engine.tagEntity(this, tag);
+    }
+
+    public void removeTag() {
+        engine.removeEntityTag(this);
+    }
+
+    public boolean hasTag(String tag) {
+        return tag.equals(this.tag);
+    }
+
+    // Internal getComponent method accessed only by ComponentMapper
+    Component getComponent(ComponentType type) {
+        return engine.getEntityComponent(this, type);
+    }
+
+    void addComponentType(ComponentType type) {
+        componentBits |= type.bit;
+    }
+
+    void removeComponentType(ComponentType type) {
+        componentBits &= ~type.bit;
+    }
+
+    void addSystemEnabledBit(long systemBit) {
+        systemEnabledBits |= systemBit;
+    }
+
+    void removeSystemEnabledBit(long systemBit) {
+        systemEnabledBits &= ~systemBit;
+    }
+
+    void reset() {
         componentBits = 0;
         systemEnabledBits = 0;
         active = false;
         removed = false;
         pendingRefresh = false;
-    }
+        uniqueId = nextUniqueId++;
-
-    protected void updateUniqueId() {
-        this.uniqueId = nextUniqueId++;
     }
 
     public String toString() {

core/src/com/me/common/ecs/EntityManager.java

@@ -1,14 +1,18 @@
 package com.me.common.ecs;
 
 import com.badlogic.gdx.utils.Array;
+import com.badlogic.gdx.utils.ObjectMap;
 
 final class EntityManager {
 
-    private Engine engine;
+    private final Engine engine;
 
-    protected Array<Entity> entities;
+    private final Array<Entity> entities;
-    protected Array<Entity> removedEntities;
+    private final Array<Entity> removedEntities;
-    protected Array<Entity> toRefresh;
+    private final Array<Entity> toRefresh;
+
+    private final ObjectMap<String, Array<Entity>> groupEntities;
+    private final ObjectMap<String, Entity> taggedEntities;
 
     EntityManager(Engine engine) {
         this.engine = engine;
@@ -16,9 +20,16 @@ final class EntityManager {
         this.entities = new Array<>(false, 16);
         this.removedEntities = new Array<>(false, 16);
         this.toRefresh = new Array<>(false, 16);
+
+        this.groupEntities = new ObjectMap<>();
+        this.taggedEntities = new ObjectMap<>();
     }
 
-    public Entity create() {
+    Array<Entity> getEntities() {
+        return entities;
+    }
+
+    Entity create() {
         Entity entity;
         if (!removedEntities.isEmpty()) {
             entity = removedEntities.removeIndex(0);
@@ -26,12 +37,11 @@ final class EntityManager {
             entity = new Entity(engine);
         }
         entity.reset();
-        entity.updateUniqueId();
         entities.add(entity);
         return entity;
     }
 
-    public void update() {
+    void update() {
         if (toRefresh.isEmpty()) {
             return;
         }
@@ -44,12 +54,52 @@ final class EntityManager {
         toRefresh.clear();
     }
 
-    public void queueRefresh(Entity entity) {
+    Array<Entity> getGroupEntities(String group) {
+        Array<Entity> entities = groupEntities.get(group);
+        if (entities == null) {
+            entities = new Array<>();
+            groupEntities.put(group, entities);
+        }
+        return entities;
+    }
+
+    void addEntityToGroup(Entity entity, String group) {
+        if (!entity.groups.contains(group)) {
+            getGroupEntities(group).add(entity);
+            entity.groups.add(group);
+        }
+    }
+
+    void removeEntityFromGroup(Entity entity, String group) {
+        getGroupEntities(group).removeValue(entity, true);
+        entity.groups.remove(group);
+    }
+
+    Entity getEntityByTag(String tag) {
+        return taggedEntities.get(tag);
+    }
+
+    void tagEntity(Entity entity, String tag) {
+        Entity previouslyTagged = taggedEntities.put(tag, entity);
+        if (previouslyTagged != null) {
+            previouslyTagged.tag = null;
+        }
+        entity.tag = tag;
+    }
+
+    void removeEntityTag(Entity entity) {
+        if (entity.tag != null) {
+            taggedEntities.remove(entity.tag);
+            entity.tag = null;
+        }
+    }
+
+    void queueRefresh(Entity entity) {
         toRefresh.add(entity);
     }
 
     private void refreshEntity(Entity entity) {
-        for (BaseSystem system : engine.systems) {
+        for (BaseSystem system : engine.getSystems()) {
             if (!(system instanceof EntitySystem)) {
                 continue;
             }
@@ -57,11 +107,20 @@ final class EntityManager {
             ((EntitySystem) system).refresh(entity);
         }
 
-        if (entity.removed) {
+        if (entity.isRemoved()) {
             engine.removeAllEntityComponents(entity.id);
             entities.removeValue(entity, true);
             removedEntities.add(entity);
+
+            // remove the entity from any groups it is in
+            for (String group : entity.groups) {
+                getGroupEntities(group).removeValue(entity, true);
+            }
+            entity.groups.clear();
+
+            removeEntityTag(entity);
         }
     }
 
+
 }

core/src/com/me/common/ecs/EntitySystem.java

@@ -10,15 +10,16 @@ public abstract class EntitySystem extends BaseSystem {
     private static final Map<Class<? extends EntitySystem>, Long> systemBits = new HashMap<>();
     private static long nextBit = 1l;
 
-    private long systemBit;
+    private final long systemBit;
-    private long typeBits;
+    private final long componentBits;
 
-    protected Array<Entity> entities;
+    private final Array<Entity> entities;
 
+    @SafeVarargs
     public EntitySystem(Engine engine, Class<? extends Component>... components) {
         super(engine);
         this.systemBit = getBitFor(getClass());
-        this.typeBits = ComponentType.getMaskBits(components);
+        this.componentBits = ComponentType.getBitsFor(components);
         this.entities = new Array<>(true, 16, Entity.class);
     }
 
@@ -29,7 +30,7 @@ public abstract class EntitySystem extends BaseSystem {
     public void process(float dt) {
         for (int i = 0, n = entities.size; i < n; i++) {
             Entity entity = entities.items[i];
-            if (!entity.removed && entity.active) {
+            if (entity.isActive()) {
                 processEntity(entity, dt);
             }
         }
@@ -37,13 +38,13 @@ public abstract class EntitySystem extends BaseSystem {
 
     public abstract void processEntity(Entity entity, float dt);
 
-    protected void refresh(Entity entity) {
+    void refresh(Entity entity) {
         boolean enabled = (entity.systemEnabledBits & systemBit) == systemBit;
-        boolean interested = (entity.componentBits & typeBits) == typeBits;
+        boolean interested = (entity.componentBits & componentBits) == componentBits;
 
         if (interested && !enabled && entity.active && !entity.removed) {
             add(entity);
-        } else if (enabled && (!interested || !entity.active || entity.removed)) {
+        } else if (enabled && (!interested || !entity.active) || entity.removed) {
             remove(entity);
         }
     }
@@ -59,7 +60,7 @@ public abstract class EntitySystem extends BaseSystem {
     }
 
 
-    static long getBitFor(Class<? extends EntitySystem> es) {
+    private static long getBitFor(Class<? extends EntitySystem> es) {
         Long bits = systemBits.get(es);
         if (bits == null) {
             bits = nextBit;

core/src/com/me/common/ecs/ListenerRegistry.java

@@ -11,15 +11,15 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-public class ListenerRegistry {
+class ListenerRegistry {
 
     private final Map<Class<? extends Event>, List<RegisteredListener>> registeredListeners;
 
-    protected ListenerRegistry() {
+    ListenerRegistry() {
         this.registeredListeners = new HashMap<>();
     }
 
-    protected void registerListener(Listener listener) {
+    void registerListener(Listener listener) {
         for (Method method : listener.getClass().getMethods()) {
             EventHandler eh = method.getAnnotation(EventHandler.class);
             if (eh == null) {
@@ -37,10 +37,9 @@ public class ListenerRegistry {
             List<RegisteredListener> executors = getRegisteredListeners(eventClass);
             executors.add(new RegisteredListener(listener, method, eventClass, eh));
         }
-
     }
 
-    protected void callEvent(Event event) {
+    void callEvent(Event event) {
         List<RegisteredListener> listeners = getRegisteredListeners(event.getClass());
         if (listeners.isEmpty()) {
             return;

core/src/com/me/common/ecs/event/RegisteredListener.java

@@ -4,11 +4,10 @@ import java.lang.reflect.Method;
 
 public class RegisteredListener {
 
-    private Listener listener;
+    private final Listener listener;
-    private Method method;
+    private final Method method;
-    private Class<? extends Event> eventType;
+    private final Class<? extends Event> eventType;
-
+    private final EventHandler eh;
-    public EventHandler eh;
 
     public RegisteredListener(Listener listener, Method method, Class<? extends Event> eventType, EventHandler eh) {
         this.listener = listener;

desktop/src/com/me/asteroids/desktop/DesktopLauncher.java

@@ -8,9 +8,10 @@ public class DesktopLauncher {
 	public static void main (String[] arg) {
 		LwjglApplicationConfiguration config = new LwjglApplicationConfiguration();
 		config.title = "Asteroids";
-		config.resizable = false;
+		config.resizable = true;
+//		config.fullscreen = false;
 		config.width = 800;
-		config.height = 600;
+		config.height = 400;
 		new LwjglApplication(new Asteroids(), config);
 	}
 }