/* ==================== 基础变量 ==================== */
:root {
    --primary: #4A90D9;
    --primary-dark: #3A7BC8;
    --primary-light: #E8F1FB;
    --accent: #FF9F43;
    --accent-dark: #E8871E;
    --success: #2ED573;
    --success-light: #E8FBF0;
    --danger: #FF4757;
    --danger-light: #FFF0F0;
    --warning: #FFA502;
    --warning-light: #FFF8E8;
    --bg: #F0F4F8;
    --card-bg: #FFFFFF;
    --text: #2C3E50;
    --text-light: #7F8C8D;
    --text-lighter: #BDC3C7;
    --border: #E3E8ED;
    --sidebar-bg: #FFFFFF;
    --radius: 16px;
    --radius-sm: 10px;
    --shadow: 0 2px 12px rgba(0,0,0,0.06);
    --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
    --sidebar-width: 220px;
    --transition: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ==================== 重置 ==================== */
* { margin: 0; padding: 0; box-sizing: border-box; -webkit-tap-highlight-color: transparent; }
html, body { height: 100%; overflow: hidden; }
body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: var(--bg);
    color: var(--text);
    font-size: 15px;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}
input, select, textarea, button { font-family: inherit; font-size: inherit; }
button { cursor: pointer; border: none; background: none; }
ul { list-style: none; }

/* ==================== 主布局 ==================== */
#app { display: flex; height: 100vh; }

/* ==================== 侧边导航 ==================== */
.sidebar {
    width: var(--sidebar-width);
    background: var(--sidebar-bg);
    display: flex;
    flex-direction: column;
    border-right: 1px solid var(--border);
    flex-shrink: 0;
    z-index: 10;
}
.sidebar-header {
    padding: 20px 16px;
    text-align: center;
    border-bottom: 1px solid var(--border);
}
.logo { font-size: 36px; }
.app-title { font-size: 18px; font-weight: 700; color: var(--primary); margin-top: 4px; }
.app-subtitle { font-size: 12px; color: var(--text-light); }

.nav-list { flex: 1; overflow-y: auto; padding: 8px; }
.nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-light);
    margin-bottom: 4px;
}
.nav-item:hover { background: var(--primary-light); color: var(--primary); }
.nav-item.active { background: var(--primary); color: #fff; }
.nav-icon { font-size: 22px; width: 28px; text-align: center; }
.nav-text { font-size: 15px; font-weight: 500; }
.sidebar-footer { padding: 8px; border-top: 1px solid var(--border); }

/* ==================== 主内容区 ==================== */
.main-content {
    flex: 1;
    overflow-y: auto;
    padding: 24px 32px;
    -webkit-overflow-scrolling: touch;
}

/* ==================== 页面标题 ==================== */
.page-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 24px;
}
.page-title { font-size: 24px; font-weight: 700; }
.page-desc { font-size: 14px; color: var(--text-light); margin-top: 4px; }

/* ==================== 卡片 ==================== */
.card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: var(--shadow);
    margin-bottom: 16px;
}
.card-title { font-size: 17px; font-weight: 600; margin-bottom: 12px; }

/* ==================== 按钮 ==================== */
.btn {
    padding: 10px 24px;
    border-radius: var(--radius-sm);
    font-size: 15px;
    font-weight: 600;
    transition: var(--transition);
    display: inline-flex;
    align-items: center;
    gap: 6px;
}
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-accent { background: var(--accent); color: #fff; }
.btn-accent:hover { background: var(--accent-dark); }
.btn-success { background: var(--success); color: #fff; }
.btn-outline { border: 2px solid var(--border); color: var(--text); background: #fff; }
.btn-outline:hover { border-color: var(--primary); color: var(--primary); }
.btn-danger { background: var(--danger); color: #fff; }
.btn-lg { padding: 14px 32px; font-size: 17px; }
.btn-sm { padding: 6px 16px; font-size: 13px; }
.btn:disabled { opacity: 0.5; cursor: not-allowed; }

/* ==================== 首页仪表盘 ==================== */
.dashboard-stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 16px;
    margin-bottom: 24px;
}
.stat-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 20px;
    box-shadow: var(--shadow);
    display: flex;
    flex-direction: column;
    align-items: center;
    text-align: center;
}
.stat-icon { font-size: 32px; margin-bottom: 8px; }
.stat-value { font-size: 32px; font-weight: 700; color: var(--primary); }
.stat-label { font-size: 13px; color: var(--text-light); margin-top: 4px; }

.quick-entry {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 16px;
    margin-bottom: 24px;
}
.quick-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 24px 20px;
    box-shadow: var(--shadow);
    text-align: center;
    cursor: pointer;
    transition: var(--transition);
}
.quick-card:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.quick-icon { font-size: 40px; margin-bottom: 12px; }
.quick-title { font-size: 16px; font-weight: 600; }
.quick-desc { font-size: 12px; color: var(--text-light); margin-top: 4px; }

.progress-section { display: flex; gap: 20px; }
.progress-item { flex: 1; }
.progress-bar-bg {
    height: 10px;
    background: var(--border);
    border-radius: 10px;
    overflow: hidden;
    margin-top: 8px;
}
.progress-bar-fill {
    height: 100%;
    background: linear-gradient(90deg, var(--primary), var(--success));
    border-radius: 10px;
    transition: width 0.5s;
}

/* ==================== 课本选择器 ==================== */
.grade-selector {
    display: flex;
    gap: 8px;
    flex-wrap: wrap;
    margin-bottom: 20px;
}
.grade-tab {
    padding: 8px 18px;
    border-radius: 20px;
    background: var(--card-bg);
    border: 2px solid var(--border);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-light);
}
.grade-tab.active { background: var(--primary); color: #fff; border-color: var(--primary); }
.grade-tab:hover:not(.active) { border-color: var(--primary); color: var(--primary); }

.unit-list { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 12px; }
.unit-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: var(--transition);
    border: 2px solid transparent;
}
.unit-card:hover { border-color: var(--primary); transform: translateY(-2px); }
.unit-card.active { border-color: var(--primary); background: var(--primary-light); }
.unit-num { font-size: 12px; color: var(--accent); font-weight: 600; }
.unit-title { font-size: 16px; font-weight: 600; margin: 4px 0; }
.unit-words { font-size: 12px; color: var(--text-light); }

/* ==================== 课本阅读 ==================== */
.reader-toolbar {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
    flex-wrap: wrap;
}
.reader-text {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 28px 32px;
    box-shadow: var(--shadow);
    margin-bottom: 16px;
}
.sentence {
    display: block;
    padding: 12px 16px;
    margin: 4px -8px;
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    font-size: 18px;
    line-height: 2;
}
.sentence:hover { background: var(--primary-light); }
.sentence.playing { background: var(--primary); color: #fff; }
.sentence-cn { display: block; font-size: 14px; color: var(--text-light); margin-top: 4px; }

.reader-controls {
    display: flex;
    align-items: center;
    gap: 8px;
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 12px 20px;
    box-shadow: var(--shadow);
    position: sticky;
    bottom: 0;
}
.control-btn {
    width: 48px; height: 48px;
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-size: 20px;
    transition: var(--transition);
    background: var(--primary-light);
    color: var(--primary);
}
.control-btn:hover { background: var(--primary); color: #fff; }
.control-btn.play-all { background: var(--primary); color: #fff; width: 56px; height: 56px; font-size: 24px; }
.control-info { flex: 1; text-align: center; font-size: 14px; color: var(--text-light); }

/* ==================== 单词卡 ==================== */
.word-section { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.word-item {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 16px;
    box-shadow: var(--shadow);
    display: flex;
    align-items: center;
    gap: 12px;
    transition: var(--transition);
}
.word-item:hover { box-shadow: var(--shadow-lg); }
.word-text { font-size: 18px; font-weight: 700; flex: 1; }
.word-phonetic { font-size: 13px; color: var(--text-light); }
.word-meaning { font-size: 14px; color: var(--text-light); }
.word-action { display: flex; gap: 6px; }
.mini-btn {
    width: 36px; height: 36px;
    border-radius: 8px;
    display: flex; align-items: center; justify-content: center;
    font-size: 16px;
    background: var(--primary-light);
    color: var(--primary);
    transition: var(--transition);
}
.mini-btn:hover { background: var(--primary); color: #fff; }

/* ==================== 词典 ==================== */
.search-bar {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
}
.search-input {
    flex: 1;
    padding: 14px 20px;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 16px;
    outline: none;
    transition: var(--transition);
}
.search-input:focus { border-color: var(--primary); }

.dict-result {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
}
.dict-word { font-size: 28px; font-weight: 700; }
.dict-phonetic { font-size: 16px; color: var(--accent); margin: 8px 0; }
.dict-pos { font-size: 14px; color: var(--text-light); font-style: italic; }
.dict-meaning { font-size: 16px; margin-top: 8px; }
.dict-example {
    margin-top: 12px;
    padding: 12px;
    background: var(--bg);
    border-radius: var(--radius-sm);
    font-size: 14px;
}
.dict-example-en { color: var(--text); }
.dict-example-cn { color: var(--text-light); margin-top: 4px; }

.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-lighter);
}
.empty-state .empty-icon { font-size: 60px; }
.empty-state .empty-text { font-size: 16px; margin-top: 12px; }

/* ==================== 单词记忆 ==================== */
.memorize-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
}
.mem-tab {
    flex: 1;
    padding: 12px;
    text-align: center;
    border-radius: var(--radius-sm);
    background: var(--card-bg);
    border: 2px solid var(--border);
    cursor: pointer;
    font-weight: 600;
    transition: var(--transition);
    color: var(--text-light);
}
.mem-tab.active { background: var(--primary); color: #fff; border-color: var(--primary); }

.flashcard {
    background: var(--card-bg);
    border-radius: 24px;
    box-shadow: var(--shadow-lg);
    min-height: 320px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 40px;
    cursor: pointer;
    transition: var(--transition);
    position: relative;
}
.flashcard:hover { transform: scale(1.02); }
.fc-word { font-size: 40px; font-weight: 700; }
.fc-phonetic { font-size: 18px; color: var(--accent); margin-top: 12px; }
.fc-meaning { font-size: 24px; color: var(--text); margin-top: 20px; }
.fc-example { font-size: 14px; color: var(--text-light); margin-top: 16px; text-align: center; }
.fc-hint { position: absolute; bottom: 16px; font-size: 13px; color: var(--text-lighter); }

.card-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
    margin-top: 20px;
}
.rate-btn {
    padding: 14px 28px;
    border-radius: var(--radius-sm);
    font-weight: 600;
    font-size: 16px;
    transition: var(--transition);
}
.rate-forgot { background: var(--danger-light); color: var(--danger); border: 2px solid var(--danger); }
.rate-hard { background: var(--warning-light); color: var(--warning); border: 2px solid var(--warning); }
.rate-good { background: var(--success-light); color: var(--success); border: 2px solid var(--success); }
.rate-easy { background: var(--primary-light); color: var(--primary); border: 2px solid var(--primary); }
.rate-btn:hover { transform: scale(1.05); }

.review-stats {
    display: flex;
    gap: 16px;
    justify-content: center;
    margin-bottom: 20px;
}
.review-stat {
    text-align: center;
    padding: 8px 20px;
    background: var(--card-bg);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow);
}
.review-stat-num { font-size: 22px; font-weight: 700; color: var(--primary); }
.review-stat-label { font-size: 12px; color: var(--text-light); }

/* 听写模式 */
.dictation-area {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 32px;
    box-shadow: var(--shadow);
    text-align: center;
}
.dictation-word-num { font-size: 14px; color: var(--text-light); margin-bottom: 16px; }
.dictation-play {
    width: 80px; height: 80px;
    border-radius: 50%;
    background: var(--primary);
    color: #fff;
    font-size: 32px;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 20px;
}
.dictation-input {
    width: 100%;
    max-width: 400px;
    padding: 14px 20px;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 18px;
    text-align: center;
    outline: none;
}
.dictation-input:focus { border-color: var(--primary); }
.dictation-result { margin-top: 16px; font-size: 18px; font-weight: 600; }

/* ==================== 口语训练 ==================== */
.speaking-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow);
    margin-bottom: 16px;
    text-align: center;
}
.speak-target { font-size: 22px; font-weight: 600; margin-bottom: 8px; }
.speak-target-en { font-size: 24px; font-weight: 700; color: var(--primary); }
.speak-target-cn { font-size: 14px; color: var(--text-light); margin-top: 4px; }
.speak-actions { display: flex; gap: 12px; justify-content: center; margin: 20px 0; }

.mic-btn {
    width: 72px; height: 72px;
    border-radius: 50%;
    background: var(--primary);
    color: #fff;
    font-size: 28px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: var(--transition);
    box-shadow: 0 4px 15px rgba(74, 144, 217, 0.4);
}
.mic-btn:hover { transform: scale(1.1); }
.mic-btn.recording { background: var(--danger); animation: pulse 1.5s infinite; }
@keyframes pulse {
    0% { box-shadow: 0 0 0 0 rgba(255, 71, 87, 0.4); }
    70% { box-shadow: 0 0 0 20px rgba(255, 71, 87, 0); }
    100% { box-shadow: 0 0 0 0 rgba(255, 71, 87, 0); }
}

.score-display {
    margin-top: 20px;
    padding: 20px;
    background: var(--bg);
    border-radius: var(--radius);
}
.score-main {
    font-size: 48px;
    font-weight: 700;
}
.score-main.high { color: var(--success); }
.score-main.mid { color: var(--warning); }
.score-main.low { color: var(--danger); }
.score-detail { display: flex; gap: 24px; justify-content: center; margin-top: 12px; }
.score-item { text-align: center; }
.score-item-label { font-size: 13px; color: var(--text-light); }
.score-item-value { font-size: 20px; font-weight: 600; }

.recognized-text {
    margin-top: 12px;
    padding: 12px;
    background: var(--primary-light);
    border-radius: var(--radius-sm);
    font-size: 16px;
}
.recognized-text .diff { color: var(--danger); font-weight: 600; }
.recognized-text .match { color: var(--success); }

/* ==================== AI对话 ==================== */
.chat-container {
    display: flex;
    flex-direction: column;
    height: calc(100vh - 120px);
}
.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 8px 0;
}
.chat-msg {
    max-width: 75%;
    padding: 14px 18px;
    border-radius: var(--radius);
    margin-bottom: 12px;
    font-size: 15px;
    line-height: 1.6;
    white-space: pre-wrap;
    word-break: break-word;
}
.chat-msg.user {
    align-self: flex-end;
    background: var(--primary);
    color: #fff;
    border-bottom-right-radius: 4px;
}
.chat-msg.ai {
    align-self: flex-start;
    background: var(--card-bg);
    box-shadow: var(--shadow);
    border-bottom-left-radius: 4px;
}
.chat-msg.ai strong { color: var(--primary); }
.chat-input-area {
    display: flex;
    gap: 8px;
    padding: 12px 0;
    border-top: 1px solid var(--border);
}
.chat-input {
    flex: 1;
    padding: 12px 18px;
    border: 2px solid var(--border);
    border-radius: 24px;
    font-size: 15px;
    outline: none;
    transition: var(--transition);
}
.chat-input:focus { border-color: var(--primary); }
.chat-send {
    width: 48px; height: 48px;
    border-radius: 50%;
    background: var(--primary);
    color: #fff;
    font-size: 20px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}
.chat-send:disabled { opacity: 0.5; }

.chat-suggestions { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 12px; }
.suggestion-chip {
    padding: 8px 16px;
    border-radius: 20px;
    background: var(--primary-light);
    color: var(--primary);
    font-size: 13px;
    cursor: pointer;
    transition: var(--transition);
}
.suggestion-chip:hover { background: var(--primary); color: #fff; }

/* ==================== 作文批改 ==================== */
.essay-editor {
    width: 100%;
    min-height: 300px;
    padding: 20px;
    border: 2px solid var(--border);
    border-radius: var(--radius);
    font-size: 16px;
    line-height: 1.8;
    outline: none;
    resize: vertical;
    font-family: inherit;
}
.essay-editor:focus { border-color: var(--primary); }
.essay-feedback {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
    margin-top: 16px;
}
.feedback-item {
    padding: 12px;
    border-radius: var(--radius-sm);
    margin-bottom: 8px;
}
.feedback-item.error { background: var(--danger-light); border-left: 4px solid var(--danger); }
.feedback-item.warning { background: var(--warning-light); border-left: 4px solid var(--warning); }
.feedback-item.suggestion { background: var(--primary-light); border-left: 4px solid var(--primary); }
.feedback-item.good { background: var(--success-light); border-left: 4px solid var(--success); }
.feedback-type { font-size: 12px; font-weight: 700; text-transform: uppercase; }
.feedback-original { font-size: 14px; color: var(--danger); text-decoration: line-through; margin-top: 4px; }
.feedback-correct { font-size: 14px; color: var(--success); margin-top: 2px; }
.feedback-explanation { font-size: 13px; color: var(--text-light); margin-top: 4px; }

/* ==================== 精准练习 ==================== */
.practice-question {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow);
    margin-bottom: 16px;
}
.question-num { font-size: 14px; color: var(--accent); font-weight: 600; }
.question-text { font-size: 18px; font-weight: 600; margin: 12px 0 20px; }
.question-options { display: flex; flex-direction: column; gap: 10px; }
.option-item {
    padding: 14px 18px;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    cursor: pointer;
    transition: var(--transition);
    font-size: 16px;
}
.option-item:hover { border-color: var(--primary); background: var(--primary-light); }
.option-item.selected { border-color: var(--primary); background: var(--primary-light); }
.option-item.correct { border-color: var(--success); background: var(--success-light); }
.option-item.wrong { border-color: var(--danger); background: var(--danger-light); }
.option-label { font-weight: 700; margin-right: 8px; color: var(--primary); }

.practice-result {
    text-align: center;
    padding: 40px;
}
.result-score { font-size: 64px; font-weight: 700; }
.result-label { font-size: 18px; color: var(--text-light); }
.result-analysis {
    margin-top: 24px;
    text-align: left;
    background: var(--bg);
    border-radius: var(--radius);
    padding: 20px;
}

/* ==================== 弹窗 ==================== */
.modal-overlay {
    display: none;
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.4);
    z-index: 1000;
    align-items: center;
    justify-content: center;
}
.modal-overlay.show { display: flex; }
.modal {
    background: #fff;
    border-radius: var(--radius);
    width: 90%;
    max-width: 560px;
    max-height: 85vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
}
.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 20px 24px;
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    background: #fff;
    z-index: 1;
}
.modal-header h2 { font-size: 20px; }
.modal-close {
    width: 36px; height: 36px;
    border-radius: 50%;
    font-size: 18px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--bg);
}
.modal-close:hover { background: var(--danger-light); }
.modal-body { padding: 24px; }

.settings-section { margin-bottom: 24px; }
.settings-section h3 { font-size: 16px; margin-bottom: 12px; color: var(--primary); }
.setting-row { display: flex; align-items: center; gap: 12px; margin-bottom: 12px; }
.setting-row label { width: 100px; font-size: 14px; color: var(--text-light); flex-shrink: 0; }
.setting-row select, .setting-row input {
    flex: 1;
    padding: 10px 14px;
    border: 2px solid var(--border);
    border-radius: var(--radius-sm);
    outline: none;
}
.setting-row select:focus, .setting-row input:focus { border-color: var(--primary); }
.setting-input { font-size: 14px; }
.setting-tip { font-size: 13px; color: var(--text-light); margin-bottom: 12px; line-height: 1.5; }
.share-icon { display: inline-block; }

/* ==================== Toast ==================== */
.toast {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: rgba(44, 62, 80, 0.95);
    color: #fff;
    padding: 12px 28px;
    border-radius: 24px;
    font-size: 15px;
    z-index: 2000;
    transition: var(--transition);
    opacity: 0;
}
.toast.show { transform: translateX(-50%) translateY(0); opacity: 1; }

/* ==================== 加载动画 ==================== */
.loading-overlay {
    display: none;
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(255,255,255,0.8);
    z-index: 3000;
    flex-direction: column;
    align-items: center;
    justify-content: center;
}
.loading-overlay.show { display: flex; }
.loading-spinner {
    width: 48px; height: 48px;
    border: 4px solid var(--border);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 0.8s linear infinite;
}
@keyframes spin { to { transform: rotate(360deg); } }
.loading-text { margin-top: 16px; color: var(--text-light); font-size: 15px; }

/* ==================== 生词本列表 ==================== */
.wordbook-list { display: flex; flex-direction: column; gap: 8px; }
.wordbook-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 18px;
    background: var(--card-bg);
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow);
}
.wordbook-word { font-weight: 700; font-size: 16px; }
.wordbook-phonetic { font-size: 13px; color: var(--accent); }
.wordbook-meaning { font-size: 14px; color: var(--text-light); }

/* ==================== 底部导航栏（手机端） ==================== */
.bottom-nav {
    display: none;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: var(--sidebar-bg);
    border-top: 1px solid var(--border);
    z-index: 100;
    padding: 6px 0 calc(6px + env(safe-area-inset-bottom, 0px));
    justify-content: space-around;
    align-items: center;
}
.bottom-nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2px;
    padding: 6px 10px;
    cursor: pointer;
    transition: var(--transition);
    color: var(--text-light);
    border-radius: var(--radius-sm);
    flex: 1;
    max-width: 80px;
}
.bottom-nav-item.active { color: var(--primary); }
.bottom-nav-icon { font-size: 22px; }
.bottom-nav-label { font-size: 11px; font-weight: 500; }

/* 手机端更多菜单弹层 */
.bottom-nav-menu {
    display: none;
    position: fixed;
    bottom: 0;
    left: 0;
    right: 0;
    background: #fff;
    border-radius: 20px 20px 0 0;
    box-shadow: 0 -4px 30px rgba(0,0,0,0.15);
    z-index: 200;
    padding: 20px 20px calc(24px + env(safe-area-inset-bottom, 0px));
    transform: translateY(100%);
    transition: transform 0.3s ease;
}
.bottom-nav-menu.show { transform: translateY(0); display: block; }
.bottom-nav-menu::before {
    content: '';
    position: fixed;
    top: 0; left: 0; right: 0; bottom: 0;
    background: rgba(0,0,0,0.3);
    z-index: -1;
    border-radius: 0;
}
.bottom-nav-menu-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 16px;
}
.bottom-nav-close {
    width: 32px; height: 32px;
    border-radius: 50%;
    background: var(--bg);
    font-size: 16px;
    display: flex; align-items: center; justify-content: center;
}
.bottom-nav-menu-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 12px;
}
.bottom-nav-menu-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    padding: 16px 8px;
    border-radius: var(--radius-sm);
    background: var(--bg);
    cursor: pointer;
    font-size: 13px;
    font-weight: 500;
    transition: var(--transition);
}
.bottom-nav-menu-item:active { background: var(--primary-light); }

/* ==================== 响应式：大桌面（>1200px） ==================== */
/* 默认布局即为此档位，无需额外媒体查询 */

/* ==================== 响应式：平板横屏 / 小桌面（1024px ~ 1200px） ==================== */
@media (max-width: 1200px) {
    :root { --sidebar-width: 200px; }
    .main-content { padding: 20px 24px; }
    .dashboard-stats { gap: 12px; }
    .stat-value { font-size: 28px; }
    .quick-entry { gap: 12px; }
}

/* ==================== 响应式：平板竖屏（768px ~ 1024px） ==================== */
@media (max-width: 1024px) {
    :root { --sidebar-width: 64px; }
    .sidebar-header { padding: 16px 8px; }
    .sidebar-header .app-title,
    .sidebar-header .app-subtitle { display: none; }
    .logo { font-size: 28px; }
    .nav-item { justify-content: center; padding: 12px 8px; }
    .nav-text { display: none; }
    .nav-icon { font-size: 22px; width: auto; }
    .sidebar-footer .nav-item { justify-content: center; }

    .main-content { padding: 20px; }
    .dashboard-stats { grid-template-columns: repeat(4, 1fr); }
    .quick-entry { grid-template-columns: repeat(4, 1fr); }
    .page-title { font-size: 22px; }
    .reader-text { padding: 20px 24px; }
    .sentence { font-size: 17px; }
}

/* ==================== 响应式：大手机 / 小平板横屏（640px ~ 768px） ==================== */
@media (max-width: 768px) {
    :root { --sidebar-width: 56px; }
    .main-content { padding: 16px; }
    .page-title { font-size: 20px; }
    .page-header { margin-bottom: 16px; }

    .dashboard-stats { grid-template-columns: repeat(2, 1fr); gap: 10px; }
    .stat-card { padding: 16px; }
    .stat-value { font-size: 24px; }
    .stat-icon { font-size: 28px; }
    .quick-entry { grid-template-columns: repeat(2, 1fr); gap: 10px; }
    .quick-card { padding: 18px 14px; }
    .quick-icon { font-size: 32px; }

    .word-section { grid-template-columns: 1fr; }
    .progress-section { flex-direction: column; gap: 12px; }

    .reader-text { padding: 16px 18px; }
    .sentence { font-size: 16px; line-height: 1.8; }
    .reader-controls { padding: 10px 14px; flex-wrap: wrap; }

    .flashcard { min-height: 260px; padding: 28px 20px; }
    .fc-word { font-size: 32px; }
    .fc-phonetic { font-size: 16px; }
    .fc-meaning { font-size: 20px; }
    .card-actions { gap: 8px; }
    .rate-btn { padding: 12px 20px; font-size: 14px; }

    .practice-question { padding: 20px; }
    .question-text { font-size: 16px; }
    .option-item { padding: 12px 14px; font-size: 15px; }

    .essay-editor { min-height: 220px; padding: 16px; font-size: 15px; }

    .chat-container { height: calc(100vh - 100px); }
    .chat-msg { max-width: 85%; font-size: 14px; }

    .dict-word { font-size: 24px; }
    .score-main { font-size: 40px; }
    .score-detail { gap: 16px; }

    .modal { width: 95%; max-height: 88vh; }
    .modal-body { padding: 16px; }
    .setting-row { flex-wrap: wrap; }
    .setting-row label { width: 100%; margin-bottom: 4px; }

    .unit-list { grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 10px; }
}

/* ==================== 响应式：手机（< 640px） ==================== */
@media (max-width: 640px) {
    /* 隐藏侧边栏，显示底部导航 */
    .sidebar { display: none; }
    .bottom-nav { display: flex; }

    #app { flex-direction: column; }
    .main-content {
        flex: 1;
        padding: 14px;
        padding-bottom: 80px;
        overflow-y: auto;
    }

    .page-title { font-size: 19px; }
    .page-desc { font-size: 13px; }
    .card { padding: 16px; }
    .card-title { font-size: 16px; }

    .dashboard-stats { grid-template-columns: repeat(2, 1fr); gap: 10px; }
    .stat-card { padding: 14px; }
    .stat-value { font-size: 22px; }
    .stat-icon { font-size: 24px; }
    .stat-label { font-size: 12px; }

    .quick-entry { grid-template-columns: repeat(2, 1fr); gap: 10px; }
    .quick-card { padding: 16px 12px; }
    .quick-icon { font-size: 30px; }
    .quick-title { font-size: 14px; }
    .quick-desc { font-size: 11px; }

    .grade-selector { gap: 6px; }
    .grade-tab { padding: 6px 14px; font-size: 13px; }
    .unit-list { grid-template-columns: repeat(auto-fill, minmax(140px, 1fr)); gap: 8px; }
    .unit-card { padding: 12px; }
    .unit-title { font-size: 14px; }

    .reader-text { padding: 14px; }
    .sentence { font-size: 15px; padding: 10px 12px; line-height: 1.7; }
    .sentence-cn { font-size: 13px; }
    .reader-controls { padding: 10px 12px; gap: 6px; }
    .control-btn { width: 40px; height: 40px; font-size: 18px; }
    .control-btn.play-all { width: 48px; height: 48px; font-size: 22px; }
    .control-info { font-size: 12px; }

    .word-item { padding: 12px; gap: 8px; }
    .word-text { font-size: 16px; }
    .mini-btn { width: 32px; height: 32px; font-size: 14px; }

    .flashcard { min-height: 240px; padding: 24px 16px; border-radius: 20px; }
    .fc-word { font-size: 28px; }
    .fc-phonetic { font-size: 15px; }
    .fc-meaning { font-size: 18px; }
    .fc-example { font-size: 13px; }
    .card-actions { flex-wrap: wrap; gap: 8px; }
    .rate-btn { padding: 10px 18px; font-size: 13px; flex: 1; min-width: 70px; text-align: center; }

    .review-stats { gap: 10px; }
    .review-stat { padding: 6px 14px; }
    .review-stat-num { font-size: 18px; }

    .dictation-area { padding: 20px 16px; }
    .dictation-play { width: 64px; height: 64px; font-size: 26px; }
    .dictation-input { font-size: 16px; padding: 12px 16px; }

    .speaking-card { padding: 18px; }
    .speak-target-en { font-size: 20px; }
    .mic-btn { width: 60px; height: 60px; font-size: 24px; }
    .score-main { font-size: 36px; }
    .score-detail { flex-wrap: wrap; gap: 12px; }

    .practice-question { padding: 16px; }
    .question-text { font-size: 15px; margin: 10px 0 16px; }
    .option-item { padding: 12px; font-size: 14px; }
    .result-score { font-size: 52px; }

    .essay-editor { min-height: 180px; padding: 14px; font-size: 14px; }
    .essay-feedback { padding: 16px; }

    .chat-container { height: calc(100vh - 90px); }
    .chat-msg { max-width: 88%; font-size: 14px; padding: 12px 14px; }
    .chat-input { font-size: 14px; padding: 10px 14px; }
    .chat-send { width: 42px; height: 42px; font-size: 18px; }
    .chat-suggestions { gap: 6px; }
    .suggestion-chip { padding: 6px 12px; font-size: 12px; }

    .search-input { padding: 12px 16px; font-size: 15px; }
    .dict-result { padding: 16px; }
    .dict-word { font-size: 22px; }

    .modal { width: 100%; max-height: 90vh; border-radius: 0; }
    .modal-header { padding: 16px; }
    .modal-header h2 { font-size: 18px; }
    .modal-body { padding: 16px; }
    .setting-row label { width: 100%; }
    .btn { padding: 10px 18px; font-size: 14px; }

    .toast { bottom: 90px; font-size: 14px; padding: 10px 20px; }
}

/* ==================== 响应式：小手机（< 380px） ==================== */
@media (max-width: 380px) {
    .main-content { padding: 10px; }
    .dashboard-stats { grid-template-columns: 1fr 1fr; gap: 8px; }
    .quick-entry { grid-template-columns: 1fr 1fr; gap: 8px; }
    .stat-value { font-size: 20px; }
    .page-title { font-size: 17px; }
    .card { padding: 14px; }
    .grade-tab { padding: 5px 10px; font-size: 12px; }
    .bottom-nav-label { font-size: 10px; }
    .bottom-nav-icon { font-size: 20px; }
}

/* ==================== 响应式：横屏手机优化 ==================== */
@media (max-width: 900px) and (orientation: landscape) and (max-height: 500px) {
    .bottom-nav { padding: 4px 0; }
    .bottom-nav-item { padding: 4px 8px; }
    .bottom-nav-icon { font-size: 20px; }
    .bottom-nav-label { font-size: 10px; }
    .main-content { padding-bottom: 64px; }
    .flashcard { min-height: 200px; padding: 20px; }
    .fc-word { font-size: 28px; }
    .chat-container { height: calc(100vh - 70px); }
}