wren/val Public Public: anyone can read this; nobody can change it.

/**

 * The spike, out loud.

 *

 * One oscillator per beep, scheduled by how much fuse is left: a slow tick

 * when it is planted, a stutter when it is about to go. No audio files, and

 * nothing is created until the person has clicked the page — a browser will

 * not start an audio context before that, and should not.

 */

/** Seconds between beeps for this much fuse left. */

export function beepInterval(fuse) {

  if (fuse <= 0) return 0;

  return Math.max(0.12, Math.min(1, fuse / 30));

}

/** The pitch rises as the fuse burns, so it is audible without watching. */

export const beepPitch = (fuse) => 760 + 620 * (1 - Math.min(1, fuse / 45));

export function makeBeeper() {

  let audio = null;

  let next = 0;

  const context = () => {

    if (audio) return audio;

    const Ctor = globalThis.AudioContext || globalThis.webkitAudioContext;

    if (!Ctor) return null;

    audio = new Ctor();

    return audio;

  };

  return {

    /** Called on a click: browsers only allow audio to start from a gesture. */

    wake() {

      const ctx = context();

      if (ctx && ctx.state === "suspended") ctx.resume();

    },

    /** Called every frame with the fuse the server last sent. */

    update(planted, fuse, now) {

      if (!planted || fuse <= 0) {

        next = 0;

        return;

      }

      if (!audio) return; // no gesture yet; nothing to play into

      if (now < next) return;

      next = now + beepInterval(fuse);

      beep(audio, beepPitch(fuse));

    },

  };

}

function beep(audio, hz) {

  const osc = audio.createOscillator();

  const gain = audio.createGain();

  osc.type = "square";

  osc.frequency.value = hz;

  gain.gain.setValueAtTime(0.0001, audio.currentTime);

  gain.gain.exponentialRampToValueAtTime(0.09, audio.currentTime + 0.01);

  gain.gain.exponentialRampToValueAtTime(0.0001, audio.currentTime + 0.09);

  osc.connect(gain).connect(audio.destination);

  osc.start();

  osc.stop(audio.currentTime + 0.1);

}