added package descriptions for JavaDoc

GameProject/src/collider/package-info.java

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+/**
+ * The package contains classes implementing a 'bounding box' area around game objects. <br>
+ * The abstract base class {@link Collider} provides the abstract method {@link Collider#collidesWith(Collider)},
+ * which needs to be implemented by child classes to detect and decide whether or not an object with such instance really collides with the other.
+ * {@link Collider} instances are to be used for game objects ({@link gameobjects}); see constructors.<br>
+ * 
+ * The benefit of seperating Colliders from visual representations is that the area for collisions can be smaller/bigger/other shape to improve game play experience.
+ */
+package collider;

GameProject/src/gameobjects/package-info.java

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+/**
+ * The package gameobjects contains all objects with a visual representation on screen. 
+ * They can be combined to use controller instances for their behavior (subclasses of {@link controller.ObjectController}).
+ * The abstract base class is {@link GameObject}, which forces child-classes to implement the method
+ * {@link GameObject#updateObject()}.
+ */
+package gameobjects;

GameProject/src/playground/package-info.java

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+/**
+ * The package playground contains all level specific logic and control of level logic.
+ * The structure and general logic (with global and local flags to be stored/used) 
+ * is provided in abstract base class {@link Playground}.<br>
+ * Child-classes implement specific logic for one level and game type (e.g. {@link SpaceInvadersLevel}).<b>
+ * 
+ * Generally, the base class {@link Playground} supports totally different game types to be implemented.
+ */
+package playground;