Curio Box · build 23 — check both devices show the same build before playing Beep-Tac-Toe
Record a word and play it ⏪ Backwards. Now try to SPEAK that backwards sound yourself, record your attempt, and reverse it — does it turn back into your word? (Harder than it sounds: your brain has never had to plan sounds in reverse.)
One device picks X, the other picks O. Each move is beeped across the room as a single musical note — no internet, no wires, just sound. Turn the volume up.
Every move is ONE pure note — a 19-note scale where the pitch itself says everything: the nine X squares are the low notes, the nine O squares the high notes, and "new game" is the very top. The note sings twice; the other device commits when it hears the same pitch both times, so a stray noise can never fake a move. Listen closely and you can learn to hear which square was played before the board even updates.
One device picks Red, the other Yellow. Each drop is beeped across the room as a single note — Red columns are the low notes, Yellow the high.
Connect-four needs only fifteen possible messages — a column for each color, plus new-game — so each drop is one pure note sung twice. The pitch is the column. Because a column can legally be played many times, the receiver also tracks whose turn it is, so a re-sent note can never drop a second disc by mistake.