* { box-sizing: border-box; margin: 0; padding: 0; }

    html, body {
      height: 100%;
      background: #000;
      color: #fff;
      font-family: 'Inter', -apple-system, system-ui, sans-serif;
      font-weight: 500;
      -webkit-font-smoothing: antialiased;
      user-select: none;
    }

    body {
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      padding: 30px;
      min-height: 100vh;
      gap: 0;
    }

    #level-desc {
      font-size: 21px;
      font-weight: 500;
      letter-spacing: -0.42px;
      color: #adadad;
      margin-bottom: 48px;
    }

    .tone-cards {
      display: flex;
      gap: 12px;
      width: 100%;
      max-width: 440px;
    }

    .tone-card {
      flex: 1;
      background: #111;
      border: 1.5px solid #222;
      border-radius: 20px;
      padding: 32px 16px;
      display: flex;
      flex-direction: column;
      align-items: center;
      gap: 0;
      transition: border-color 0.2s;
      cursor: default;
    }

    .tone-card.playing {
      border-color: rgba(255,255,255,0.5);
    }

    /* When answerable, card glows subtly on hover */
    .tone-card.answerable {
      cursor: pointer;
    }
    .tone-card.answerable:hover {
      border-color: rgba(255,255,255,0.35);
    }
    .tone-card.answerable:active {
      border-color: rgba(255,255,255,0.6);
    }

    .speaker-btn {
      width: 64px;
      height: 64px;
      border-radius: 50%;
      background: #fff;
      border: none;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: transform 0.15s ease, opacity 0.15s;
      flex-shrink: 0;
    }
    .speaker-btn:hover { transform: scale(1.05); }
    .speaker-btn:active { transform: scale(0.95); }
    .speaker-btn:disabled { opacity: 0.3; cursor: default; transform: none; }
    .speaker-btn svg { width: 24px; height: 24px; }

    /* answerable state: speaker button pulses white slightly */
    .tone-card.answerable .speaker-btn {
      box-shadow: 0 0 0 0 rgba(255,255,255,0.15);
    }

    #play-both-btn {
      margin-top: 20px;
      height: 52px;
      padding: 0 32px;
      border-radius: 58px;
      background: transparent;
      border: 1.5px solid rgba(255,255,255,0.25);
      color: #fff;
      font-family: inherit;
      font-weight: 500;
      font-size: 15px;
      letter-spacing: -0.3px;
      cursor: pointer;
      transition: border-color 0.15s, transform 0.15s;
    }
    #play-both-btn:hover { border-color: rgba(255,255,255,0.6); }
    #play-both-btn:active { transform: scale(0.97); }
    #play-both-btn:disabled { opacity: 0.25; cursor: default; transform: none; }

    #feedback {
      font-size: 16px;
      font-weight: 500;
      letter-spacing: -0.32px;
      min-height: 24px;
      margin-top: 32px;
      color: rgba(255,255,255,0.45);
      text-align: center;
    }
    #feedback.correct { color: #fff; }
    #feedback.wrong   { color: rgba(255,255,255,0.45); }