AndEngine for Android Game Development Cookbook: AndEngine is a simple but powerful 2D game engine that's ideal for developers who want to create mobile games. This cookbook will get you up to speed with the latest features and techniques quickly and practically.

In this chapter, we're going to start working with all of the wonderful entities included in AndEngine. Entities provide us with a base foundation that every object displayed within our game world will rely on, be it the score text, the background image, the player's character, buttons, and everything else. One way to think of this is that any object in our game which has the ability to be placed, via AndEngine's coordinate system, is an entity at its most basic level. In this chapter, we're going to start working with Entity objects and many of its subtypes in order to allow us to make the most out of them in our own games.

The AndEngine game engine follows the entity-component model. The entity-component design is very common in a lot of game engines today, and for a good reason. It's easy to use, it's modular, and it is extremely useful in the sense that all game objects can be traced back to the single, most basic Entity object. The entity-component model can be thought of as the "entity" portion referring to the most basic level of the game engine's object system. The Entity class handles only the most basic data that our game objects rely on, such as position, rotation, color, attaching and detaching to and from the scene, and more. The "component" portion refers to the modular subtypes of the Entity class, such as the Scene, Sprite, Text, ParticleSystem, Rectangle, Mesh, and every other object which can be placed within our game. The components are meant to handle more specific tasks, while the entity is meant to act as a base foundation that all components will rely on...

AndEngine's primitive types include Line, Rectangle, Mesh, and Gradient objects. In this topic, we're going to focus on the Mesh class. Meshes are useful for creating more complex shapes in our games which can have an unlimited amount of uses. In this recipe, we're going to use Mesh objects to build a house as seen in the the following figure:

Here, we come to the topic which might be considered to be the most necessary aspect to creating any 2D game. Sprites allow us to display 2D images on our scene which can be used to display buttons, characters/avatars, environments and themes, backgrounds, and any other entity in our game which may require representation by means of an image file. In this recipe, we'll be covering the various aspects of AndEngine's Sprite entities which will give us the information we need to continue to work with Sprite objects later on in more complex situations.

Text is an important part of game development as it can be used to dynamically display point systems, tutorials, descriptions, and more. AndEngine also allows us to create text styles which suit individual game types better by specifying customized Font objects. In this recipe, we're going to create a Text object, which updates itself with the current system time as well as correct its position every time the length of the string grows or shrinks. This will prepare us for the use of Text objects in cases where we need to display scores, time, and other non-specific dynamic string situations.

Rotating entities relative to the position of other entities in 2D space is a great function to know. The uses for relative rotation are limitless and always seems to be a "hot topic" for newer mobile game developers. One of the more prominent examples of this technique being used is in tower-defense games, which allows a tower's turret to aim towards the direction that an enemy, non-playable character is walking. In this recipe, we're going to introduce a method of rotating our Entity objects in order to point them in the direction of a given x/y position. The following image displays how we will create an arrow on the scene, which will automatically point to the position of the circle image, wherever it moves to:

Overriding an Entity object's onManagedUpdate() method can be extremely useful in all types of situations. By doing so, we can allow our entities to execute code every time the entity is updated through the update thread, occuring many times per second unless the entity is set to ignore updates. There are so many possibilities including animating our entity, checking for collisions, producing timed events, and much more. Using our Entity objects's onManagedUpdate() method also saves us from having to create and register new timer handlers for time-based events for a single entity.

AndEngine provides us with what are known as modifiers and entity modifiers. Through the use of these modifiers we can apply neat effects to our entities with great ease. These modifiers apply specific changes to an Entity object over a defined period of time, such as movement, scaling, rotation, and more. On top of that, we can include listeners and ease functions to entity modifiers for full control over how they work, making them some of the most powerful-to-use methods for applying certain types of animation to our Scene object in AndEngine.

Particle systems can provide our games with very attractive effects for many different events in our games, such as explosions, sparks, gore, rain, and much more. In this chapter, we're going to cover AndEngine's ParticleSystem classes which will be used to create customized particle effects that will suit our every need.