Overlap trigger: detect player entering a zone and do something once

Pattern: EventActorBeginOverlap → CastTo<BP_Character>(Object=OtherActor) → Cast Succeeded → DoOnce → [your action here]. Key pins: EventActorBeginOverlap outputs 'OverlappedActor' and 'OtherActor'. CastTo input is 'Object', exec outputs are 'Cast Succeeded' and 'Cast Failed'. DoOnce exec output is 'Completed'.