Here is a list of all documented files with brief descriptions:

audio.cpp
audio.h
background.cpp
background.h
collision.cpp
collision.h
engine.cpp
engine.h
entity.cpp
entity.h
gamestate.cpp
gamestate.h
image.cpp
image.h
input.cpp
input.h
level.cpp
level.h
map.cpp
map.h
model.cpp
model.h
object.cpp
object.h
PerlinNoise.cpp
PerlinNoise.h
physics-tmp.cpp
physics-tmp.h
sdl_check.h
stage.cpp
stage.h
tile.cpp
tile.h
tileset.cpp
tileset.h