Game subsystem: persistent game manager with auto-init

SETUP: Create Blueprint inheriting UGameInstanceSubsystem (or UWorldSubsystem for level-scoped). Override Initialize(Collection) to set up. Override Deinitialize to clean up. Add game variables here (Score, PlayTime, Settings). ACCESS FROM ANYWHERE: GetGameInstance → GetSubsystem(BP_GameSubsystem) → CastTo<BP_GameSubsystem> → access variables. WHY: Subsystems auto-create, auto-destroy, and don't need FindActor. Better than GameInstance for well-organized systems. UGameInstanceSubsystem persists across levels. UWorldSubsystem is recreated each level.

DoOnce — execute the output only the first time it is called

Has 'Reset' exec input to allow it to fire again. Default bStartClosed=false means it fires first time.

Create widget, add to viewport, and store reference

Pattern: EventBeginPlay → CreateWidget(OwningPlayer=GetPlayerController, WidgetType=WBP_MyWidget) → SetVariable(HUDWidget=ReturnValue) → CastTo<WBP_MyWidget>(HUDWidget) → Cast Succeeded → AddToViewport(ZOrder=0). Always store widget reference in a variable. CreateWidget inputs: 'OwningPlayer' (PlayerController) and 'WidgetType' (class). Exec in='execute', exec out='then'.

SetInputModeGameAndUI — set input for both game and UI

SetInputMode UIOnly — give all input to UI (show cursor)

Make HitResult — construct a HitResult struct manually

CreateWidget — create a UserWidget instance

Always pass a valid PlayerController as OwningPlayer. Cast the ReturnValue to your specific widget class.

SetInputModeUIOnly — set input to UI only

EnableInput — allow this actor to receive input events

Must call EnableInput(GetPlayerController(0)) before BindAction/BindAxis events fire on the actor.

CreateWidget — create widget instance from class

K2Node_CreateWidget. Class is the Widget Blueprint class reference.