DrawDebugLine — draw debug line in world

UKismetSystemLibrary::DrawDebugLine.

PrintString — print debug text to screen and log

UKismetSystemLibrary::PrintString. Default duration 2.0s.

PrintString — print debug text to screen and log

PrintString — print text to screen and log (debug only)

Inputs: 'InString' (NOT 'String' or 'Text'). Duration in seconds (-1 = default 5s). Disable in shipping builds — always gate with #if !UE_BUILD_SHIPPING or remove before release.

DrawDebugSphere — draw debug sphere in world

FlushPersistentDebugLines — clear all persistent debug draw

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.

Execution flow has a broken / missing wire

Why: An execution pin (the white triangle pins, not data pins) has no wire feeding into or out of it. UE5 can't determine when this node should run. Fix: Click and drag from the white-triangle exec OUTPUT of one node to the white-triangle exec INPUT of the next. Every node in an execution sequence must be chained — orphan nodes are silently skipped (warnings) or crash compile (errors).

Blueprint

A visual scripting asset (.uasset) that defines runtime behavior without C++. Compiles to bytecode the engine executes.

Common Blueprint mistakes and how to fix them

MISTAKE 1: Calling GetAllActorsOfClass every Tick. FIX: Cache results in BeginPlay or use delegates/tags instead. MISTAKE 2: Not checking IsValid before using object references. FIX: Always IsValid → Branch → Is Valid before dereferencing. MISTAKE 3: Using hard references to large assets in variables. FIX: Use Soft Object References + AsyncLoadAsset. MISTAKE 4: Tick enabled on many actors doing heavy work. FIX: SetActorTickInterval(0.1) for non-critical logic, or use Timers. MISTAKE 5: Casting to specific class without checking IsValid first. FIX: CastTo has 'Cast Failed' output — always handle it. MISTAKE 6: Modifying array elements by getting then setting a copy. FIX: Use 'Array Set' with index to modify in-place. MISTAKE 7: Creating widget every time it's shown. FIX: Create once → cache reference → show/hide with SetVisibility or Add/RemoveFromParent.