This inheritance list is sorted roughly, but not completely, alphabetically:

[detail level 12345]

▼CBlock	Block without special physics and attributes
▼CActive
CBell
CBush
CClock
▼CContainer	Container is multi-purpose container for blocks
CConverter
CFilter
CWorkbench	Workbench allows craft from multiple sources. There can be up to 2 products. Also can be used as container of smaller size
CDoor
▼CFalling
▼CAnimal
CDwarf
CPredator
CRabbit
CBox	Box represents falling inventory
CLiquid
▼CWeapon	Weapon class represents simple weapons as sticks, pebbles and so on. Also is used as base class for more special weapons. Weapon of SKY substance is abyss block, everything that touches abyss will be destroyed
CAxe
CHammer
CPick
CShovel
CGrass
CIlluminator
CRainMachine
CTelegraph
▼CArmour
CBoots
CHelmet
CBucket
CInformer	The Informer class, provides various information
CLadder
CMedKit
CPlate
▼CText
CMap
CBlockManager	This class is used for creating and deleting blocks, also for loading them from file
CCraftItem
CCraftList	This class represents craft recipe
CCraftManager
▼CInventory	Provides block ability to contain other blocks inside
CBox	Box represents falling inventory
CBucket
CBush
CContainer	Container is multi-purpose container for blocks
CDwarf
CRainMachine
CLongLat
▼CQObject
CActive
CPlayer	This class contains information specific to player and interface for manipulating him
▼CVirtScreen	This class provides base for all screens for freg
CScreen
▼CQThread
CIThread	Keyboard input thread for curses screen for freg
CPreloadThread
CWorld	World provides global physics and shred connection
CShredStorage
▼CWeather
CShred
CWorldMap
▼CXy
▼CXyz
CActive
CDeferredAction	Deferred Action is used when some action needs to be done at next physics turn
CPlayer	This class contains information specific to player and interface for manipulating him