Here are the classes, structs, unions and interfaces with brief descriptions:

[detail level 123]

Nboost
Ntype_erasure
Cserializable
Ncmpnt
CSorter
Nfmt
Cformatter< nlohmann::json >
Ngfx
CIndexBuffer
CLine
CMesh
CShader
CTexture	Holds and manages textures for use with meshes in sprites
CVAO
CVertex
CVertexBuffer	Buffer that holds data for the vertices for OpenGL
Ngobj	Namespace for things relating to GameObject, other than GameObject itself
CPath	An object that represents where a GameObject or a range of GameObjects exists in the Engine.
Citerator	Iterator member class for Path
CPathBase	Starts a range with an arbitrary GameObject
CPathDir	Given a range of GameObjects, generates a range of all of those GameObjects children
CPathFilter	Internal PathNode that takes a range of GameObjects on the left, and filters the range to only GameObjects fulfilling a predicate
CPathName	Internal PathNode that takes a range of GameObjects on the left, and filters the range to only GameObjects matching a given name
CPathNode	Internal type for computing Paths
Cpath_iterator	Iterator type, refers to a GameObject, and holds onto a reference to a PathNode to determine its range
CPathRoot	Path Node that represents the Root object in the Engine, and provides a starting point for a Path
CPathUp	Internal Path Node that takes a range of GameObjects on the left, and transforms the range into the parent of every GameObject in the range
Nsys	Type of elements in a basic_json container
CPlayerTurn
CScoring	Component that is responsible for managing the gameplay board, where cards are placed by Players.
CTable	The system responsible for facilitating communication between gameplay components (Players, Deck, and Board).
CAudioSystem
CColliderSystem
CDebugDraw
CEditor
CInput	System responsible for handling inputs and sending messages when they occur.
CJson
CMessaging	Component that is responsible for managing the gameplay board, where cards are placed by Players.
CnewSystemStub
CVertex
COpenGL
COptions
CParticleManager	System to store, render, and manage particles
CSceneManager
CTestRunner
Nth
CFactory
CLibrary
CBezier
CMemberFunction
CAction
CActionList	Component that stores all actions currently affecting the parent entity.
CAffineMatrix
CAudioObject	Audio system using FMOD with all declarations needed for basic audio playback
CBackground	The component tthat holds the texture behind everything.
CBehavior
CBoard	Component that is responsible for managing the gameplay board, where cards are placed by Players.
CBroadcastMessageAction	An action that broadcasts a message once it has finished executing.
CButton	A class that can be "activated" to broadcast a message.
CButtonMessage
CCard
CCardBehavior
CCategorizedHand
CChangeColorAction	An action that changes the color (and alpha) of a sprite.
CChangeOpacityAction	An action that changes the opacity of an entity (as compared to ChangeColorAction, which changes the entire color).
CChildrenHandeler	A container for child objects
CCollider
CCollisionMessage
CComponent
CConfirmDestructiveActionScene
CControllerButton	Helper class used by Controllers to handle the logic of knowing when a button is pressed down or not.
CControllerHoldButton	Derived version of ControllerButton.
CcontrollerInputTracker
CControllers	Class that detects whenever controllers are plugged in and broadcasts whenever any of them do an input.
CControllerStick	Helper class that assists Controllers by managing when a stick should be considered pressed or not.
CCreditsScene
CDeck	Component that represents a deck of playing cards.
CDrawCardMessage
CEngine
CEntity
CFilteredSelector	A derived version of selector that only selects from Input if the inputtingDeviceID matches a value inside the internal filter.
CFlags
CGameObject	the base class for the engine, most things inherit from this.
CKey	Key class to be used as a key when holding GameObjects (or unique pointers to game objects) in <key, value> datasets
CGameRules	An indicator that loops through a parents' nodes children and can "select" them on keypress.
CHandBehavior
CHandFinder
CHandRating
CKeyPressedMessage
CKeys	Class that can interact with the keyboard.
CLoadSceneAction	An action that broadcasts a message once it has finished executing.
CLogging
CMainMenuScene
CMainScene
CMenu	A menu that organizes its parents' children (in the node) either horizontally or vertically.
CPositioningInformation
CMenuPosition	Menu Position is a component that simply stores where in a menu an item/entity is.
CMessage
CMouse	Class that tracks mouse position and detects whenever a mouse button is pressed.
CMoveEntityAction	An action that moves an Entity based on its current position.
CMoveToPointAction	An action that moves an object to a specific point in the game world.
CMoveVerticalAction	Moves an entity vertically from where it is currently positioned.
CNewActionStub	BRIEF.
CNewComponentStub
CNewMessageStub
CNode	Manages the heirarchical structure between Systems and Entities.
COptionsScene
CParticle	Struct for passing around all the data a particle has, before a particle is added to a Particle Block
CParticleBlock	A container for holding and updating particles that are all the same type
CParticleEmitter	An object that manages many of a single type of particle
CParticleGenerator	A Component that generates several types of particles, by holding several ParticleEmitters
CParticleSpawner	Creates Particles, based on initial conditions set in the editor, with potential randomness
CPathException
CPauseScene
CPhysics
CPlayAudioMessage
CPlayCardMessage
CPlayer	The component responsible for storing information relevant to the player.
CPlayerCountScene
CPlayerHand
CPlayerJoinScene	Component that handles players connecting / disconnecting input devices in the "connect controllers" scene.
CRoot
CScene
CSceneState
CSelectable
CSelector	An indicator that loops through a parents' nodes children and can "select" them on keypress.
CSetMessageEnabledAction	Sets receive messages to either disabled or enabled.
CSplashScreenScene
CSprite	A component that renders an image on an entity, or text
CSystem
CTransform
CTutorialScene
CVector4D
CVertex
CWinScreenScene	An indicator that loops through a parents' nodes children and can "select" them on keypress.