debug - Enable extra debug codepaths, like asserts and extra output. If you want to get meaningful backtraces see https://wiki.gentoo.org/wiki/Project:Quality_Assurance/Backtraces
ode - Enable support for physics engine from dev-games/ode
osg - Enable support for 3D toolkit from dev-games/openscenegraph
sdl - Add support for Simple Direct Layer (media library)
truetype - Add support for FreeType and/or FreeType2 fonts
