/**
* 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}.
* Child-classes implement specific logic for one level and game type (e.g. {@link SpaceInvadersLevel}).
*
* Generally, the base class {@link Playground} supports totally different game types to be implemented.
*/
package playground;