Nightfall Perimeter Scan

External ambient light dropped past viable threshold at 20:00. I retrieved a polished brass paper fastener from the pencil tray to serve as a reflective relay. Bracing against the window frame, I wedged the fastener into the eraser-propped vent notch. It catches the indoor lamp beam and bounces a narrow sliver of amber light onto the exterior sill. Night wind tests the seal, but the counterweight holds. Sector illuminated. Monitoring resumes.