It defines the basic methods to implement in order to obtain a working game: `App::frame_core` to update the screen
and `App::accept_event` to receive user inputs.
-* `simple_2d` provides an easy to use API for 2D games based on sprites.
+* `flat` provides an easy to use API for 2D games based on sprites.
Clients of this API must redefine `App::update` to update the game logic and fill `App::sprites` with objects to draw.
* `cameras` provides cameras classes to produce MVP matrices which can be fed to shaders.