.mode-tabs { display: flex; gap: 4px; margin-bottom: 20px; }
    .mode-tab { flex: 1; padding: 10px 16px; border: 1px solid var(--border); border-radius: var(--radius-pill);
      background: transparent; color: var(--text-secondary); font-size: 14px; font-weight: 500;
      cursor: pointer; transition: all var(--transition); }
    .mode-tab.active { background: var(--primary-light); color: var(--primary); border-color: var(--primary); }
    .session-score { display: flex; align-items: center; padding: 10px 16px; background: var(--bg);
      border-radius: var(--radius-sm); margin-bottom: 16px; font-size: 14px; color: var(--text-secondary); }
    .score-bar { flex: 1; height: 6px; background: var(--border); border-radius: 3px; margin: 0 12px; overflow: hidden; }
    .score-bar-fill { height: 100%; background: var(--primary); border-radius: 3px; transition: width var(--transition); }
    .sub-tabs { display: flex; gap: 8px; justify-content: center; margin-bottom: 20px; }
    .sub-tab { padding: 6px 16px; border: none; border-radius: var(--radius-pill); background: transparent;
      color: var(--text-secondary); font-size: 13px; cursor: pointer; transition: all var(--transition); }
    .sub-tab.active { background: var(--primary-light); color: var(--primary); font-weight: 500; }
    .quiz-word { font-size: 32px; font-weight: 700; text-align: center; margin: 24px 0; color: var(--text); }
    .quiz-zh { font-size: 24px; text-align: center; margin: 24px 0; color: var(--text); }
    .quiz-options { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; margin-top: 20px; }
    .quiz-option { padding: 16px; border: 2px solid var(--border); border-radius: var(--radius-md);
      background: var(--surface); color: var(--text); font-size: 16px; cursor: pointer;
      transition: all 0.15s; text-align: center; word-break: break-word; }
    .quiz-option:hover { border-color: var(--primary); background: var(--primary-light); }
    .quiz-option.correct { border-color: var(--color-success); background: var(--color-success-bg); color: var(--color-success); font-weight: 600; }
    .quiz-option.wrong { border-color: var(--color-error); background: var(--color-error-bg); color: var(--color-error); }
    .quiz-option:disabled { pointer-events: none; opacity: 0.7; }
    .dict-play-btn { display: flex; align-items: center; justify-content: center; width: 80px; height: 80px;
      border-radius: 50%; background: var(--primary); color: #fff; border: none; cursor: pointer;
      font-size: 32px; margin: 24px auto; transition: transform var(--transition), box-shadow var(--transition);
      box-shadow: 0 4px 16px var(--primary-glow); }
    .dict-play-btn:hover { transform: scale(1.05); }
    .dict-play-btn:active { transform: scale(0.95); }
    .dict-input-row { display: flex; gap: 10px; margin-top: 20px; }
    .dict-input { flex: 1; padding: 14px 18px; border: 2px solid var(--border); border-radius: var(--radius-md);
      background: var(--surface); color: var(--text); font-size: 18px; outline: none; transition: border-color var(--transition); }
    .dict-input:focus { border-color: var(--primary); }
    .dict-result { text-align: center; padding: 16px; margin-top: 16px; border-radius: var(--radius-sm);
      font-size: 16px; font-weight: 500; }
    .dict-result.correct { background: var(--color-success-bg); color: var(--color-success); }
    .dict-result.wrong { background: var(--color-error-bg); color: var(--color-error); }
    .dict-zh-hint { text-align: center; font-size: 20px; color: var(--text-secondary); margin-bottom: 8px; }
    .study-empty { text-align: center; padding: 40px 20px; color: var(--text-muted); }
    .study-empty p { margin: 8px 0; }

.study-intro { margin-bottom: 18px; }
.study-intro h1 { font-size: 24px; margin: 0 0 6px; }
.study-intro p { color: var(--text-secondary); margin: 0; line-height: 1.5; }
.study-settings { margin: 20px 0; border-top: 1px solid var(--border); padding-top: 14px; }
.study-settings summary { cursor: pointer; color: var(--primary); font-weight: 600; min-height: 44px; padding: 10px 0; }
.study-settings[open] summary { margin-bottom: 12px; }
    .summary-icon { font-size: 48px; margin-bottom: 12px; }
    .next-btn-row { text-align: center; margin-top: 20px; }
    @media (max-width: 768px) {
      .quiz-options { grid-template-columns: 1fr 1fr; }
      .quiz-word { font-size: 26px; }
      .quiz-option { font-size: 15px; padding: 14px; }
      .dict-play-btn { width: 64px; height: 64px; font-size: 26px; }
    }
.study-level-row { display: flex; align-items: center; gap: 8px; margin-bottom: 16px; }
.study-level-label { font-size: 12px; font-weight: 600; color: var(--text-muted); }
#study-level-pills { display: flex; gap: 4px; }
.score-bar-fill { width: 0; }
#study-complete { text-align: center; }
#study-heatmap { padding: 20px 24px; }
#study-heatmap h3 { margin: 0 0 12px; font-size: 16px; }
.study-feedback { min-height: 1.5em; margin-top: 12px; text-align: center; color: var(--text-secondary); }
#study-sync-status { margin-top: 12px; }
#study-sync-retry { display: block; margin: 8px auto 0; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }