src/audio/Cheer.js

/**
 * Cheer — Web Audio chimes and arpeggios used on correct answers / mastery / level-up.
 */

let ctx = null;
function ensure() { if (!ctx) { try { ctx = new (window.AudioContext || window.webkitAudioContext)(); } catch (e) {} } return ctx; }

function tone(c, freq, when, dur = 0.45, gain = 0.18, type = 'triangle') {
  const o = c.createOscillator(), g = c.createGain();
  o.type = type; o.frequency.value = freq;
  g.gain.setValueAtTime(0, when);
  g.gain.linearRampToValueAtTime(gain, when + 0.02);
  g.gain.exponentialRampToValueAtTime(0.001, when + dur);
  o.connect(g).connect(c.destination);
  o.start(when); o.stop(when + dur + 0.05);
}

export const Cheer = {
  enabled: true,
  prime() { ensure(); },
  small() {
    if (!this.enabled) return;
    const c = ensure(); if (!c) return;
    const now = c.currentTime;
    [523.25, 659.25, 783.99, 1046.5].forEach((f, i) => tone(c, f, now + i * 0.08));
  },
  master() {
    if (!this.enabled) return;
    const c = ensure(); if (!c) return;
    const now = c.currentTime;
    [523.25, 659.25, 783.99, 1046.5, 1318.51, 1567.98, 2093.0].forEach((f, i) =>
      tone(c, f, now + i * 0.07, 0.6, 0.22, i % 2 ? 'sine' : 'triangle')
    );
  },
  levelUp() {
    this.master();
  },
};