/* ========== 全局重置与基础 ========== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
  }
  
  body {
    background: #f4f7fc;
    font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    padding: 24px 16px 40px;
    color: #1e293b;
    line-height: 1.5;
    min-height: 100vh;
    position: relative;
  }
  
  @supports (font-variation-settings: normal) {
    body { font-family: 'Inter Variable', sans-serif; }
  }
  
  .view-container {
    max-width: 1400px;
    margin: 0 auto;
  }
  
  .study-view, .quiz-view {
    transition: opacity 0.2s;
  }
  
  .hidden-view {
    display: none !important;
  }
  
  /* ========== 语言切换按钮 ========== */
  .lang-switch {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 1500;
    background: white;
    border: 1px solid #bbd6f0;
    border-radius: 40px;
    padding: 8px 16px;
    font-weight: 600;
    color: #1e4a7a;
    box-shadow: 0 4px 10px rgba(0, 0, 0, 0.05);
    cursor: pointer;
    backdrop-filter: blur(4px);
    background: rgba(255, 255, 255, 0.9);
    transition: 0.15s;
  }
  
  .lang-switch:hover {
    background: #1e4a7a;
    color: white;
  }
  
  /* ========== 头部 ========== */
  .header {
    margin-bottom: 28px;
  }
  
  h1 {
    font-size: 2.2rem;
    font-weight: 700;
    letter-spacing: -0.02em;
    background: linear-gradient(145deg, #0f2b3d, #1b4a6b);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    margin-bottom: 6px;
    display: flex;
    align-items: center;
    gap: 10px;
  }
  
  .subhead {
    font-size: 1rem;
    color: #475569;
    border-left: 4px solid #3b82f6;
    padding-left: 16px;
    font-weight: 400;
    margin-top: 4px;
  }
  
  /* ========== 黄金口诀卡片 ========== */
  .golden-rules {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 14px;
    margin-bottom: 32px;
  }
  
  .rule-card {
    background: white;
    padding: 18px 14px;
    border-radius: 24px;
    box-shadow: 0 8px 18px rgba(0, 0, 0, 0.04);
    border: 1px solid #e9eef3;
    transition: transform 0.15s;
  }
  
  .rule-card:hover {
    transform: translateY(-3px);
    box-shadow: 0 14px 24px rgba(0, 35, 70, 0.08);
    border-color: #cbdffc;
  }
  
  .rule-emoji {
    font-size: 2rem;
    margin-bottom: 8px;
  }
  
  .rule-text {
    font-weight: 700;
    font-size: 1.2rem;
    color: #0b2b40;
    margin-bottom: 6px;
  }
  
  .rule-desc {
    color: #4b6589;
    font-size: 0.9rem;
    font-weight: 500;
    background: #f0f6ff;
    display: inline-block;
    padding: 4px 12px;
    border-radius: 40px;
  }
  
  /* ========== 章节通用 ========== */
  .section-title {
    display: flex;
    align-items: baseline;
    margin: 32px 0 18px 0;
  }
  
  .section-title h2 {
    font-size: 1.6rem;
    font-weight: 650;
    color: #163a5c;
    letter-spacing: -0.01em;
  }
  
  .section-title span {
    margin-left: 14px;
    font-size: 0.9rem;
    background: #dbeafe;
    color: #1e4a7a;
    padding: 4px 12px;
    border-radius: 30px;
    font-weight: 500;
  }
  
  /* ========== 后缀卡片网格 ========== */
  .suffix-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 18px;
  }
  
  .suffix-cat {
    background: white;
    border-radius: 24px;
    padding: 18px 16px 20px;
    box-shadow: 0 6px 12px rgba(0, 0, 0, 0.02);
    border: 1px solid #dee7ef;
  }
  
  .cat-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 16px;
    border-bottom: 2px dashed #cbd5e1;
    padding-bottom: 12px;
  }
  
  .cat-header h3 {
    font-size: 1.4rem;
    font-weight: 700;
  }
  
  .noun { color: #0b5e7c; }
  .verb { color: #0f7b4e; }
  .adj { color: #b25700; }
  .adv { color: #7b3f9e; }
  
  .suffix-list {
    display: flex;
    flex-wrap: wrap;
    gap: 10px 12px;
  }
  
  .suffix-item {
    background: #f8fafc;
    padding: 6px 12px;
    border-radius: 40px;
    font-size: 0.9rem;
    font-weight: 500;
    border: 1px solid #e2e8f0;
    color: #1e293b;
    transition: all 0.1s;
    cursor: default;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.02);
  }
  
  .suffix-item strong {
    font-weight: 700;
    margin-right: 5px;
  }
  
  .suffix-item .example {
    font-size: 0.8rem;
    color: #5e7180;
    margin-left: 4px;
    font-weight: 400;
  }
  
  .noun .suffix-item { border-left: 3px solid #0b5e7c; }
  .verb .suffix-item { border-left: 3px solid #0f7b4e; }
  .adj .suffix-item { border-left: 3px solid #b25700; }
  .adv .suffix-item { border-left: 3px solid #7b3f9e; }
  
  /* ========== 线索表格区 ========== */
  .clue-wrapper {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 22px;
    margin-top: 8px;
  }
  
  .clue-panel {
    background: white;
    border-radius: 24px;
    padding: 20px;
    border: 1px solid #e2eaf2;
    box-shadow: 0 6px 14px rgba(0, 0, 0, 0.02);
  }
  
  .clue-panel h3 {
    font-size: 1.3rem;
    font-weight: 650;
    margin-bottom: 16px;
    display: flex;
    align-items: center;
    gap: 8px;
  }
  
  .clue-table {
    width: 100%;
    border-collapse: collapse;
  }
  
  .clue-table th {
    text-align: left;
    font-weight: 600;
    font-size: 0.8rem;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: #64748b;
    padding-bottom: 8px;
    border-bottom: 1px solid #e2e8f0;
  }
  
  .clue-table td {
    padding: 10px 4px 10px 0;
    border-bottom: 1px solid #edf2f7;
    vertical-align: top;
  }
  
  .clue-table tr:last-child td { border-bottom: none; }
  
  .clue-signal {
    font-weight: 650;
    color: #0b3b5c;
    font-family: 'SF Mono', 'Menlo', monospace;
    background: #eef4ff;
    padding: 2px 8px;
    border-radius: 20px;
    font-size: 0.85rem;
    display: inline-block;
  }
  
  .clue-example {
    color: #2c4c6e;
    font-weight: 500;
  }
  
  .example-en {
    font-style: italic;
    color: #537188;
    font-size: 0.9rem;
  }
  
  /* ========== V-ing / V-ed 双卡片 ========== */
  .verbform-duo {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 22px;
    margin: 20px 0 30px;
  }
  
  .form-card {
    background: white;
    border-radius: 24px;
    padding: 20px;
    border: 1px solid #dee9f2;
  }
  
  .ing-card { border-top: 6px solid #2563eb; }
  .ed-card { border-top: 6px solid #b45309; }
  
  .form-card h4 {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: 16px;
  }
  
  .form-list {
    list-style: none;
  }
  
  .form-list li {
    margin-bottom: 12px;
    font-size: 0.95rem;
    display: flex;
    flex-wrap: wrap;
    align-items: baseline;
    gap: 6px;
  }
  
  .tag {
    background: #eef2f6;
    padding: 2px 10px;
    border-radius: 30px;
    font-size: 0.75rem;
    font-weight: 600;
    color: #334155;
    text-transform: uppercase;
  }
  
  /* ========== 随机小贴士 ========== */
  .tip-bar {
    margin-top: 36px;
    background: linear-gradient(105deg, #e6f0fa 0%, #d9e9fa 100%);
    border-radius: 60px;
    padding: 16px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    border: 1px solid #bbd6f0;
  }
  
  .tip-content {
    font-size: 1.1rem;
    font-weight: 500;
    color: #153e5c;
  }
  
  #randomTipBtn {
    background: white;
    border: none;
    padding: 10px 24px;
    border-radius: 60px;
    font-weight: 600;
    color: #1e4a7a;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.05);
    cursor: pointer;
    font-size: 0.95rem;
    border: 1px solid #aac8e4;
    transition: 0.15s;
  }
  
  #randomTipBtn:hover {
    background: #1e4a7a;
    color: white;
    border-color: #1e4a7a;
  }
  
  .footer-note {
    margin-top: 30px;
    text-align: right;
    color: #62748c;
    font-size: 0.85rem;
  }
  
  /* ========== 浮动按钮组 ========== */
  .float-actions {
    position: fixed;
    bottom: 28px;
    right: 24px;
    display: flex;
    flex-direction: column;
    gap: 12px;
    z-index: 1000;
  }
  
  .float-btn {
    width: 56px;
    height: 56px;
    border-radius: 30px;
    background: white;
    border: none;
    box-shadow: 0 8px 18px rgba(0, 20, 50, 0.15);
    font-size: 26px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid #cbdffc;
    transition: 0.15s;
    color: #1e4a7a;
  }
  
  .float-btn:hover {
    transform: scale(1.05);
    background: #eef4ff;
  }
  
  .float-btn.modal-trigger {
    background: #1e4a7a;
    color: white;
    border: none;
  }
  
  .float-btn.modal-trigger:hover {
    background: #0f3552;
  }
  
  /* ========== 模态框通用 ========== */
  .modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.3);
    backdrop-filter: blur(3px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
    visibility: hidden;
    opacity: 0;
    transition: 0.2s;
  }
  
  .modal-overlay.show {
    visibility: visible;
    opacity: 1;
  }
  
  .modal-card {
    background: white;
    max-width: 600px;
    width: 90%;
    border-radius: 32px;
    padding: 28px;
    box-shadow: 0 30px 40px rgba(0, 0, 0, 0.2);
    border: 1px solid #dbe7f3;
  }
  
  .modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 18px;
  }
  
  .modal-header h3 {
    font-size: 1.8rem;
    font-weight: 700;
    color: #0b2b40;
  }
  
  .close-modal {
    background: none;
    border: none;
    font-size: 28px;
    cursor: pointer;
    color: #6b85a0;
  }
  
  .modal-table {
    width: 100%;
    border-collapse: collapse;
  }
  
  .modal-table th {
    text-align: left;
    padding: 8px 4px;
    border-bottom: 1px solid #dce5ec;
    color: #3a6685;
  }
  
  .modal-table td {
    padding: 10px 4px;
    border-bottom: 1px solid #eef2f6;
  }
  
  .modal-note {
    margin-top: 18px;
    background: #eef4fa;
    border-radius: 20px;
    padding: 10px 16px;
    font-size: 0.9rem;
  }
  
  /* ========== 测验视图 ========== */
  .quiz-container {
    max-width: 700px;
    margin: 40px auto;
    background: white;
    border-radius: 40px;
    padding: 32px 30px;
    box-shadow: 0 20px 30px rgba(0, 0, 0, 0.05);
    border: 1px solid #dee9f2;
  }
  
  .quiz-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 20px;
    flex-wrap: wrap;
    gap: 10px;
  }
  
  .quiz-header-left {
    display: flex;
    gap: 10px;
    align-items: center;
  }
  
  .quiz-header h2 {
    font-size: 2rem;
    font-weight: 650;
    color: #163a5c;
  }
  
  .back-to-study {
    background: #eef2f6;
    border: none;
    padding: 10px 22px;
    border-radius: 40px;
    font-weight: 600;
    cursor: pointer;
  }
  
  .quiz-toolbar {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
    flex-wrap: wrap;
    align-items: center;
  }
  
  .lib-selector {
    background: #f0f6ff;
    border-radius: 40px;
    padding: 4px;
    display: inline-flex;
    border: 1px solid #cbdffc;
  }
  
  .lib-btn {
    padding: 8px 20px;
    border-radius: 40px;
    border: none;
    background: transparent;
    font-weight: 600;
    cursor: pointer;
  }
  
  .lib-btn.active {
    background: #1e4a7a;
    color: white;
  }
  
  .add-word-btn {
    background: #e6f3ec;
    border: none;
    padding: 8px 18px;
    border-radius: 40px;
    font-weight: 600;
    color: #1d6742;
    cursor: pointer;
  }
  
  .settle-btn {
    background: #f3eefe;
    border: none;
    padding: 8px 18px;
    border-radius: 40px;
    font-weight: 600;
    color: #4b3b7c;
    cursor: pointer;
  }
  
  .quiz-word {
    text-align: center;
    font-size: 4.2rem;
    font-weight: 700;
    margin: 20px 0 12px;
    letter-spacing: -0.02em;
  }
  
  .pos-options {
    display: flex;
    gap: 12px;
    justify-content: center;
    flex-wrap: wrap;
    margin: 28px 0 20px;
  }
  
  .pos-btn {
    background: #f4f9ff;
    border: 2px solid #d4e2f0;
    padding: 14px 26px;
    border-radius: 60px;
    font-size: 1.2rem;
    font-weight: 600;
    color: #1e405e;
    cursor: pointer;
    transition: all 0.1s;
    min-width: 100px;
  }
  
  .pos-btn.selected {
    background: #1e4a7a;
    border-color: #1e4a7a;
    color: white;
  }
  
  .pos-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    background: #e2e8f0;
  }
  
  .feedback-area {
    background: #f8fcfd;
    border-radius: 28px;
    padding: 20px 22px;
    margin: 20px 0 22px;
    border: 1px solid #cde1f0;
  }
  
  .feedback-message {
    font-size: 1.2rem;
    font-weight: 500;
    margin-bottom: 8px;
  }
  
  .feature-hint {
    color: #2d5575;
    background: #e1edfb;
    display: inline-block;
    padding: 8px 18px;
    border-radius: 40px;
  }
  
  .next-btn {
    background: #1e4a7a;
    color: white;
    border: none;
    padding: 16px 32px;
    border-radius: 60px;
    font-weight: 700;
    font-size: 1.2rem;
    width: 100%;
    cursor: pointer;
    transition: 0.1s;
  }
  
  .next-btn:disabled {
    background: #b6cbd9;
    cursor: default;
  }
  
  .quiz-stats {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 16px;
    color: #456f8c;
  }
  
  #resetStatsBtn {
    background: none;
    border: none;
    font-size: 1.2rem;
    cursor: pointer;
    color: #7f9ab3;
    padding: 4px 8px;
    border-radius: 30px;
    transition: 0.1s;
  }
  
  #resetStatsBtn:hover {
    background: #e2eaf3;
    color: #1e4a7a;
  }
  
  /* ========== 添加单词模态框 ========== */
  #addWordModal .modal-card {
    max-width: 450px;
  }
  
  .form-group {
    margin-bottom: 16px;
  }
  
  .form-group label {
    display: block;
    font-weight: 600;
    margin-bottom: 6px;
  }
  
  .form-group input,
  .form-group select {
    width: 100%;
    padding: 12px;
    border-radius: 20px;
    border: 1px solid #d4e2f0;
    font-size: 1rem;
  }
  
  .save-btn {
    background: #1e4a7a;
    color: white;
    border: none;
    padding: 14px;
    border-radius: 40px;
    width: 100%;
    font-weight: 700;
    cursor: pointer;
  }
  
  /* ========== 结算分享卡片 ========== */
  .share-card {
    max-width: 350px;
    text-align: center;
  }
  
  .share-card h3 {
    font-size: 1.8rem;
    margin-bottom: 16px;
  }
  
  .share-stats {
    font-size: 1.2rem;
    margin: 16px 0;
  }
  
  .share-btn {
    background: #1e4a7a;
    color: white;
    border: none;
    padding: 12px 24px;
    border-radius: 60px;
    margin: 8px;
    cursor: pointer;
    font-weight: 600;
  }
  
  /* ========== 响应式 ========== */
  @media (max-width: 900px) {
    .golden-rules { grid-template-columns: repeat(2, 1fr); }
    .suffix-grid { grid-template-columns: repeat(2, 1fr); }
    .clue-wrapper { grid-template-columns: 1fr; }
    .verbform-duo { grid-template-columns: 1fr; }
  }
  
  @media (max-width: 560px) {
    .golden-rules { grid-template-columns: 1fr; }
    .suffix-grid { grid-template-columns: 1fr; }
    h1 { font-size: 1.8rem; }
    .quiz-word { font-size: 2.8rem; }
  }