Sound: recorded SFX layer + a touch-easier CPU

Wire the new assets/audio/*.wav samples over the synth SFX:
- Ball hits: per-side tennis-player / tennis-opponent on serve & return,
  now with a stadium reverb tail (same convolver as umpire/aww).
- Crowd: tennis-applaus on your points/games (louder on big moments);
  tennis-aww when the opponent scores or you're eaten (reverb tail).
- Ambient bed: tennis-ambient-loop from first tap, 500Hz lowcut, low vol.
- Zombie music: zombie-mode loop when splatter kicks in (800Hz lowcut),
  fades out for the 1:1 sudden-death duel and back in after.
- Headshots: random headshot-1/-2 on every zombie kill (killZombie).

audio.js: sfx() one-shot player w/ rate+reverb opts, loopBed() beds with
duck/fade, aww() wrapper, hotter reverb send on the umpire voice.

Also: normal opponent aiFlub 0.09 -> 0.14 (a little easier to beat).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

audio.js

@@ -29,7 +29,9 @@ export function voice(name, delay = 0, rate = 1) {
   const play = buf => {
     const src = ac.createBufferSource(); src.buffer = buf;
     src.playbackRate.value = rate; // < 1 = slower and lower — the umpire's dark register
-    src.connect(ac.destination); src.connect(reverb(ac)); // dry + center-court echo
+    src.connect(ac.destination); // dry
+    const send = ac.createGain(); send.gain.value = 1.8; // umpire rides a wetter PA tail than the crowd sfx
+    src.connect(send).connect(reverb(ac)); // extra reverb send — the big-stadium announcer echo
     src.start(ac.currentTime + delay);
   };
   if (VOICE[name]) return play(VOICE[name]);
@@ -40,6 +42,62 @@ export function voice(name, delay = 0, rate = 1) {
     .catch(() => say(name.replace(/_/g, ' '), delay));
 }
 
+// Recorded one-shot SFX (assets/audio/tennis-*.wav): ball hits, applause, the crowd's aww.
+// Same load-once-then-cache pattern as voice(), but dry (no PA reverb) and with a volume knob.
+const SFX = {};
+export function sfx(name, vol = 1, opts = {}) {
+  const ac = audio();
+  const play = buf => {
+    const src = ac.createBufferSource(); src.buffer = buf;
+    if (opts.rate) src.playbackRate.value = opts.rate; // < 1 stretches it a touch longer (and lower)
+    const g = ac.createGain(); g.gain.value = vol;
+    src.connect(g).connect(ac.destination);
+    if (opts.reverb) g.connect(reverb(ac)); // wet stadium tail on top of the dry sample
+    src.start();
+  };
+  if (SFX[name]) return play(SFX[name]);
+  fetch('assets/audio/' + name + '.wav')
+    .then(r => { if (!r.ok) throw 0; return r.arrayBuffer(); })
+    .then(ab => ac.decodeAudioData(ab))
+    .then(buf => { SFX[name] = buf; play(buf); })
+    .catch(() => {}); // missing sample = silence, never a thrown error mid-rally
+}
+
+// the crowd's groan — stretched a touch and pushed through the PA reverb for a longer, wetter sigh
+export function aww(vol = 1) { sfx('tennis-aww', vol * 0.5, { reverb: true }); }
+
+// Looping background beds (scene atmosphere, mode music): each starts once, highpass 'lowcut' + quiet gain.
+const beds = new Map(); // file -> {ac, g, vol} once playing (null while loading); see fadeBed
+function loopBed(file, lowcut, vol) {
+  if (beds.has(file)) return;
+  beds.set(file, null);
+  const ac = audio();
+  fetch('assets/audio/' + file + '.wav')
+    .then(r => { if (!r.ok) throw 0; return r.arrayBuffer(); })
+    .then(ab => ac.decodeAudioData(ab))
+    .then(buf => {
+      const src = ac.createBufferSource(); src.buffer = buf; src.loop = true;
+      const hp = ac.createBiquadFilter(); hp.type = 'highpass'; hp.frequency.value = lowcut;
+      const g = ac.createGain(); g.gain.value = vol;
+      src.connect(hp).connect(g).connect(ac.destination); src.start();
+      beds.set(file, { ac, g, vol });
+    })
+    .catch(() => beds.delete(file)); // failed start (decode/network) can retry next call
+}
+export const ambient = () => loopBed('tennis-ambient-loop', 500, 0.035);  // whole-scene atmosphere, from first tap
+export const zombieMusic = () => loopBed('zombie-mode', 800, 0.2);         // background music once splatter kicks in
+
+// duck a bed to silence (out=true) or back to its base level over `secs` — the sudden-death duel mutes the music
+function fadeBed(file, out, secs = 0.7) {
+  const b = beds.get(file);
+  if (!b) return;
+  const t = b.ac.currentTime;
+  b.g.gain.cancelScheduledValues(t);
+  b.g.gain.setValueAtTime(b.g.gain.value, t); // anchor at current level so a mid-fade toggle stays smooth
+  b.g.gain.linearRampToValueAtTime(out ? 0 : b.vol, t + secs);
+}
+export const zombieDuck = out => fadeBed('zombie-mode', out);
+
 let sysVoice = null;
 export function say(text, delay = 0) { // fallback when a recorded umpire line is missing
   try {