Sprint system with stamina drain and recovery

Pattern: Variables bIsSprinting(bool), Stamina(float)=100, MaxStamina(float)=100, SprintSpeed(float)=1200, WalkSpeed(float)=600, DrainRate(float)=20, RecoverRate(float)=10. Sprint pressed: bIsSprinting=true → SetMaxWalkSpeed(SprintSpeed). Released: bIsSprinting=false → SetMaxWalkSpeed(WalkSpeed). Tick: Branch(bIsSprinting) → Stamina -= DrainRate*DT. Else: Stamina += RecoverRate*DT. Clamp(0, Max). If Stamina<=0 → force stop sprint.

Blueprint communication: 4 methods ranked by coupling

1. DIRECT REFERENCE (tightest coupling): Get reference → CastTo<BP_Other> → call function. Use when: actor A always knows about actor B (e.g. Player → HUD). 2. CAST via GetAllActorsOfClass (loose): find → cast → call. Use when: you need to find actors dynamically. 3. EVENT DISPATCHER (loose): Owner calls dispatcher → listeners receive event. Use when: one actor notifies many others (e.g. death notification). 4. BLUEPRINT INTERFACE (loosest): Call interface message → any implementing actor responds. Use when: multiple different actor types should respond to same action (e.g. 'Interact'). 5. GAME INSTANCE (persistent): Store shared data in GameInstance → GetGameInstance → Cast. Use when: data must survive level loads.

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.

Elevator or moving platform with timeline and trigger

Pattern: Variables StartLocation(Vector), EndLocation(Vector). BeginPlay: SET StartLocation=GetActorLocation. Timeline MoveTimeline(Alpha 0→1 over Duration). Trigger overlap/button press → Play Timeline. Timeline Update: VLerp(StartLocation, EndLocation, Alpha) → SetActorLocation(Self, Result, bSweep=true). Finished: Delay → Reverse Timeline.

Spawn system with wave management for enemies

Pattern: Variables CurrentWave(int)=0, EnemiesAlive(int)=0, EnemiesPerWave(Array<int>). StartWave: CurrentWave++ → SET EnemiesAlive=EnemiesPerWave[CurrentWave]. Timer looping: Branch(SpawnedThisWave < EnemiesPerWave[CurrentWave]) → SpawnActor(EnemyClass, RandomSpawnPoint) → SpawnedThisWave++. OnEnemyDeath: EnemiesAlive-- → Branch(EnemiesAlive <= 0) → StartNextWave or Victory.

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AddImpulse — apply instant impulse to physics body

One-shot force. bVelChange=true treats Impulse as velocity change.

SpawnEmitterAtLocation — spawn a legacy Cascade particle system

Legacy Cascade system. Prefer Niagara (SpawnSystemAtLocation) for new projects.

Health and damage system with ApplyDamage and EventAnyDamage

Dealing damage: Event → ApplyDamage(TargetActor, BaseDamage, InstigatorController, DamageCauser, DamageTypeClass). Receiving: EventAnyDamage → Damage output → Subtract_FloatFloat(CurrentHealth, Damage) → FClamp(Result, 0, MaxHealth) → SET CurrentHealth → Branch(CurrentHealth <= 0) → True: DestroyActor. Initialize CurrentHealth=MaxHealth in BeginPlay.

GetTargetArmLength — get spring arm distance