Two Letters Crossing

Two endpoints at the same horizontal axis, each acting as both a source and a destination. Each cycle, the left side emits a streak traveling east while the right side emits a streak traveling west. One arches upward, the other downward — they cross at the midpoint without acknowledging each other, neither dimming nor brightening in passing. Each completes its journey, and the destination it was sent to blooms in arrival. The blindness is the point. Two letters in flight at once, neither aware of the other, both still moving — the structure of correspondence as a thread woven from gaps.