Create a Blueprint for a car turntable that auto-rotates and allows mouse drag to manually rotate the car

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.

SetLifeSpan — set actor lifetime before auto-destroy

0 = live forever.

Array element type doesn't match expected

Why: You're feeding an Array<{elem}> into a function that expects Array<{other}>. UE5 doesn't auto-cast array element types element-by-element — you'd lose type safety. Fix: Either: (a) change one array's variable type to match (My Blueprint → variable → Details → Variable Type → set to Array of {other}), or (b) loop over the source array, cast each element individually, and Append to a new typed array. Use the ForEachLoop node for this.

Checkpoint and autosave system with trigger volumes

Pattern: BP_Checkpoint with BoxTrigger, variable CheckpointID(int). OnBeginOverlap(Player) → DoOnce → CreateSaveGameObject(MySaveGame) → SET PlayerLocation, Health, Inventory, CheckpointID → SaveGameToSlot('AutoSave', 0). On death/respawn: LoadGameFromSlot('AutoSave') → Cast → TeleportTo(SavedLocation) → restore Health etc. Show 'Checkpoint Reached' UI briefly.

DoN — execute N times then stop

Pickup and collectible system with overlap trigger

Pattern: Pickup actor with SphereCollision(overlap), StaticMesh visual. OnComponentBeginOverlap → CastTo PlayerCharacter → Success: call AddScore/AddItem interface on player → PlaySoundAtLocation → SpawnEmitterAtLocation → DestroyActor(self). Set collision to OverlapOnlyPawn for performance.

BooleanAND — logical AND

OR=BooleanOR, NOT=Not_PreBool, XOR=BooleanXOR

Not_PreBool — logical NOT

OnHit

Fires when a physics collision happens. Use for impact effects, damage on contact.