Karts : Contains classes that deal with the properties, models and physics of karts.
Items : Defines the various collectibles and weapons of STK.
Io : Contains generic utility classes for file I/O (especially XML handling).
Input : Contains classes for input management (keyboard and gamepad).
Guiengine/Widgets : Contains the various types of widgets supported by the GUI engine.
Note that all input comes through this module too. See module States_screens for the actual STK GUI screens.
Guiengine : Contains the generic GUI engine (contains the widgets and the backing logic for event handling, the skin, screens and dialogs).
Graphics : This module contains the core graphics engine, that is mostly a thin layer on top of irrlicht providing some additional features we need for STK (like particles, more scene node types, mesh manipulation tools, material management, etc.).
Font : This module stores font files and tools used to draw characters in STK.
Config : This module handles the user configuration, the supertuxkart configuration file (which contains options usually not edited by the player) and the input configuration file.
Challenges : This module handles the challenge system, which locks features (tracks, karts modes, etc.) until the user completes some task.
Audio : This module handles audio (sound effects and music).