Flag semaphore was the primary method of ship-to-ship and ship-to-shore communication for over two centuries. Before radio, sailors used colored flags held in precise arm positions to spell out messages across vast distances. Today it's nearly extinct — a fascinating visual language that most people have never encountered. This project exists to preserve and teach it.
Signal Fire is an interactive flag semaphore simulator. You can type messages and watch an animated signaler spell them out letter by letter, practice recognizing semaphore signals in a timed drill, decode messages as they're signaled, or browse the complete alphabet reference. It covers all 26 letters plus numbers, with historically accurate arm positions.
Each letter of the alphabet maps to a unique pair of arm angles, traditionally described using clock-face positions (e.g., "K" pairs 12 o'clock with 7:30). The signaler figure uses SVG transforms — CSS rotate() on arm groups anchored at the shoulder joints — to position the arms accurately. The animation pipeline cycles through each character: transition to position, pause, transition to next, creating a realistic signaling rhythm.