/**
 * PathFinder - IELTS Learning Protocol
 * AI-Powered English Deep Learning System
 *
 * 系统名称：PathFinder
 * 视觉风格：学院风 Academic
 */

:root {
    /* 主色调 */
    --primary-dark: #2c3e50;
    --primary-red: #8b0000;
    --bg-cream: #faf9f7;
    --bg-white: #ffffff;
    --border-soft: #e8e4de;
    --text-dark: #2c3e50;
    --text-gray: #666;
    --text-light: #888;

    /* 间距 */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;

    /* 圆角 */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 12px;

    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.06);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.08);
    --shadow-hover: 0 6px 20px rgba(139,0,0,0.12);
}

/* 通用样式重置 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
    background: var(--bg-cream);
    color: var(--text-dark);
    line-height: 1.6;
    min-height: 100vh;
}

/* 学院风字体 */
.font-serif {
    font-family: Georgia, 'Times New Roman', 'STSong', serif;
}

/* 容器 */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-xl);
}

/* ==================== */
/* 顶部导航栏 */
/* ==================== */
.header {
    background: var(--bg-white);
    border-bottom: 1px solid var(--border-soft);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-inner {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--space-md) 0;
}

.logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary-dark), var(--primary-red));
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-weight: 700;
    font-size: 1.1rem;
}

.logo-text {
    font-family: Georgia, serif;
    font-size: 1.3rem;
    font-weight: 700;
    color: var(--primary-dark);
}

.logo-text span {
    font-size: 0.7rem;
    display: block;
    font-weight: 400;
    color: var(--text-light);
    font-family: -apple-system, 'PingFang SC', 'Microsoft YaHei', sans-serif;
    letter-spacing: 1px;
}

.nav {
    display: flex;
    gap: var(--space-lg);
}

.nav-item {
    font-size: 0.9rem;
    color: var(--text-gray);
    text-decoration: none;
    padding: var(--space-sm) var(--space-md);
    border-radius: var(--radius-sm);
    transition: all 0.2s;
}

.nav-item:hover {
    color: var(--primary-red);
    background: var(--bg-cream);
}

.nav-item.active {
    color: var(--primary-red);
    font-weight: 600;
}

/* ==================== */
/* 英雄区 - 首页 banner */
/* ==================== */
.hero {
    background: var(--bg-cream);
    color: var(--text-dark);
    padding: 40px 0 32px;
    position: relative;
    text-align: center;
}

.hero-row {
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
}

.hero-brand {
    display: inline-block;
    text-align: center;
    max-width: 480px;
    background: linear-gradient(135deg, var(--primary-dark) 0%, #1a252f 50%, #0d1519 100%);
    color: white;
    padding: 28px 40px 24px;
    border-radius: 16px;
    position: relative;
    overflow: hidden;
    box-shadow: 0 8px 32px rgba(44,62,80,0.25);
}

.hero-brand::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: url("data:image/svg+xml,%3Csvg width='60' height='60' viewBox='0 0 60 60' xmlns='http://www.w3.org/2000/svg'%3E%3Cg fill='none' fill-rule='evenodd'%3E%3Cg fill='%23ffffff' fill-opacity='0.03'%3E%3Cpath d='M36 34v-4h-2v4h-4v2h4v4h2v-4h4v-2h-4zm0-30V0h-2v4h-4v2h4v4h2V6h4V4h-4zM6 34v-4H4v4H0v2h4v4h2v-4h4v-2H6zM6 4V0H4v4H0v2h4v4h2V6h4V4H6z'/%3E%3C/g%3E%3C/g%3E%3C/svg%3E");
    opacity: 0.5;
    pointer-events: none;
}

.hero-brand .hero-badge {
    display: inline-block;
    background: rgba(139,0,0,0.3);
    border: 1px solid rgba(139,0,0,0.5);
    padding: 4px 14px;
    border-radius: 20px;
    font-size: 0.7rem;
    margin-bottom: 8px;
    letter-spacing: 1px;
    position: relative;
    z-index: 1;
}

.hero-brand h1 {
    font-family: Georgia, serif;
    font-size: 2.4rem;
    font-weight: 700;
    margin: 0 0 4px;
    letter-spacing: 2px;
    position: relative;
    z-index: 1;
}

.hero-brand p {
    font-size: 0.95rem;
    opacity: 0.85;
    font-weight: 300;
    margin: 0;
    white-space: nowrap;
    position: relative;
    z-index: 1;
}

/* 兼容旧版 hero */
.hero-content { position:relative; z-index:1; text-align:center; max-width:700px; margin:0 auto; }
.hero-content .hero-badge { display:inline-block; background:rgba(139,0,0,0.3); border:1px solid rgba(139,0,0,0.5); padding:var(--space-xs) var(--space-md); border-radius:20px; font-size:0.75rem; margin-bottom:var(--space-lg); letter-spacing:1px; color:white; }
.hero-content h1 { font-family:'Playfair Display',serif; font-size:2.5rem; font-weight:700; margin-bottom:var(--space-md); letter-spacing:2px; color:white; }
.hero-content p { font-size:1.1rem; opacity:0.85; font-weight:300; margin-bottom:var(--space-xl); line-height:1.8; color:white; }
.hero-actions { display:flex; gap:var(--space-md); justify-content:center; }

.btn {
    display: inline-flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-md) var(--space-xl);
    border-radius: var(--radius-md);
    font-size: 0.95rem;
    font-weight: 500;
    text-decoration: none;
    transition: all 0.3s;
    cursor: pointer;
    border: none;
}

.btn-primary {
    background: var(--primary-red);
    color: white;
}

.btn-primary:hover {
    background: #6b0000;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(139,0,0,0.3);
}

.btn-secondary {
    background: transparent;
    color: white;
    border: 1px solid rgba(255,255,255,0.3);
}

.btn-secondary:hover {
    background: rgba(255,255,255,0.1);
    border-color: rgba(255,255,255,0.5);
}

/* ==================== */
/* 统计卡片 + 词典 横排区域 */
/* ==================== */
.dict-section {
    background: var(--bg-cream);
    padding: 0;
}

.stats-row {
    display: flex;
    align-items: stretch;
    gap: var(--space-lg);
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 var(--space-xl) 48px;
}

.stats {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--space-md);
    flex: 1;
}

.dict-section .dict-card {
    width: 320px;
    flex-shrink: 0;
}

.stat-card {
    background: var(--bg-white);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    padding: var(--space-md) var(--space-sm);
    text-align: center;
    box-shadow: var(--shadow-sm);
}

.stat-icon {
    font-size: 1.5rem;
    margin-bottom: 2px;
}

.stat-number {
    font-family: Georgia, serif;
    font-size: 1.6rem;
    font-weight: 700;
    color: var(--primary-dark);
}

.stat-label {
    font-size: 0.8rem;
    color: var(--text-light);
    margin-top: 1px;
}

/* ==================== */
/* 模块卡片区域 */
/* ==================== */
.section {
    padding: var(--space-2xl) 0;
}

.section-header {
    text-align: center;
    margin-bottom: var(--space-2xl);
}

.section-title {
    font-family: Georgia, serif;
    font-size: 1.8rem;
    color: var(--primary-dark);
    margin-bottom: var(--space-sm);
}

.section-subtitle {
    font-size: 0.95rem;
    color: var(--text-light);
}

.modules-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--space-xl);
}

.module-card {
    background: var(--bg-white);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    padding: var(--space-xl);
    cursor: pointer;
    transition: all 0.3s;
    position: relative;
    overflow: hidden;
}

.module-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: var(--primary-red);
    transform: scaleY(0);
    transition: transform 0.3s;
}

.module-card:hover {
    border-color: var(--primary-red);
    box-shadow: var(--shadow-hover);
    transform: translateY(-4px);
}

.module-card:hover::before {
    transform: scaleY(1);
}

.module-icon {
    width: 56px;
    height: 56px;
    background: var(--primary-red);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    margin-bottom: var(--space-lg);
    transition: transform 0.3s;
}

.module-card:hover .module-icon {
    transform: scale(1.1);
}

.module-title {
    font-size: 1.15rem;
    font-weight: 600;
    color: var(--primary-dark);
    margin-bottom: var(--space-sm);
}

.module-desc {
    font-size: 0.85rem;
    color: var(--text-light);
    line-height: 1.7;
    margin-bottom: var(--space-lg);
}

.module-tags {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-sm);
}

.module-tag {
    display: inline-block;
    background: var(--bg-cream);
    color: var(--text-gray);
    font-size: 0.7rem;
    padding: var(--space-xs) var(--space-sm);
    border-radius: var(--radius-sm);
}

.module-progress {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    margin-top: var(--space-md);
    padding-top: var(--space-md);
    border-top: 1px solid var(--border-soft);
}

.progress-bar {
    flex: 1;
    height: 4px;
    background: #e8e8e8;
    border-radius: 2px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary-red);
    border-radius: 2px;
    transition: width 0.3s;
}

.progress-text {
    font-size: 0.75rem;
    color: var(--text-light);
    white-space: nowrap;
}

/* ==================== */
/* 页脚 */
/* ==================== */
.footer {
    background: var(--primary-dark);
    color: rgba(255,255,255,0.7);
    padding: var(--space-2xl) 0;
    text-align: center;
    margin-top: var(--space-2xl);
}

.footer-logo {
    font-family: Georgia, serif;
    font-size: 1.2rem;
    color: white;
    margin-bottom: var(--space-sm);
}

.footer-text {
    font-size: 0.8rem;
}

.footer-text a {
    color: rgba(255,255,255,0.9);
    text-decoration: none;
}

/* ==================== */
/* 响应式设计 */
/* ==================== */
@media (max-width: 1024px) {
    .modules-grid {
        grid-template-columns: repeat(2, 1fr);
    }

    .stats-row {
        flex-direction: column;
        align-items: center;
    }

    .stats {
        grid-template-columns: repeat(4, 1fr);
    }

    .dict-section .dict-card {
        max-width: 480px;
        width: 100%;
    }
}

@media (max-width: 768px) {
    .container {
        padding: 0 var(--space-md);
    }

    .nav {
        display: none;
    }

    .hero-brand {
        max-width: 100%;
        border-radius: 0;
        padding: 24px 16px 20px;
    }

    .hero-brand h1 {
        font-size: 1.8rem;
    }

    .hero-brand p {
        font-size: 0.8rem;
        white-space: normal;
    }

    .hero-actions {
        flex-direction: column;
        align-items: center;
    }

    .modules-grid {
        grid-template-columns: 1fr;
    }

    .stats-row {
        flex-direction: column;
        padding: 0 var(--space-md) 32px;
    }

    .stats {
        grid-template-columns: repeat(2, 1fr);
    }

    .dict-section .dict-card {
        width: 100%;
        max-width: 100%;
    }

    .stat-card {
        padding: var(--space-lg);
    }
}

/* ==================== */
/* 面包屑导航 */
/* ==================== */
.breadcrumb {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.85rem;
    color: var(--text-light);
    margin-bottom: var(--space-lg);
}

.breadcrumb a {
    color: var(--text-light);
    text-decoration: none;
}

.breadcrumb a:hover {
    color: var(--primary-red);
}

.breadcrumb-sep {
    color: #ccc;
}

/* ==================== */
/* 子模块列表页 */
/* ==================== */
.module-header {
    background: var(--bg-white);
    border-bottom: 1px solid var(--border-soft);
    padding: var(--space-2xl) 0;
}

.module-header-inner {
    display: flex;
    align-items: center;
    gap: var(--space-xl);
}

.module-header-icon {
    width: 80px;
    height: 80px;
    background: var(--primary-red);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 2.5rem;
}

.module-header-info h1 {
    font-family: Georgia, serif;
    font-size: 1.8rem;
    color: var(--primary-dark);
    margin-bottom: var(--space-xs);
}

.module-header-info p {
    color: var(--text-gray);
    font-size: 0.95rem;
}

.submodules-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--space-lg);
}

.submodule-card {
    background: var(--bg-white);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-md);
    padding: var(--space-xl);
    display: flex;
    gap: var(--space-lg);
    cursor: pointer;
    transition: all 0.3s;
}

.submodule-card:hover {
    border-color: var(--primary-red);
    box-shadow: var(--shadow-md);
}

.submodule-number {
    width: 44px;
    height: 44px;
    background: var(--bg-cream);
    border-radius: var(--radius-md);
    display: flex;
    align-items: center;
    justify-content: center;
    font-family: Georgia, serif;
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--primary-red);
    flex-shrink: 0;
}

.submodule-content h3 {
    font-size: 1rem;
    font-weight: 600;
    color: var(--primary-dark);
    margin-bottom: var(--space-xs);
}

.submodule-content p {
    font-size: 0.85rem;
    color: var(--text-light);
    margin-bottom: var(--space-sm);
}

.submodule-meta {
    display: flex;
    gap: var(--space-md);
    font-size: 0.75rem;
    color: var(--text-light);
}

.submodule-meta span {
    display: flex;
    align-items: center;
    gap: 4px;
}

/* ==================== */
/* 学习内容页 */
/* ==================== */
.lesson-container {
    display: grid;
    grid-template-columns: 1fr 360px;
    gap: var(--space-xl);
    padding: var(--space-xl) 0;
}

.lesson-main {
    background: var(--bg-white);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.lesson-content {
    padding: var(--space-xl);
}

.lesson-title {
    font-family: Georgia, serif;
    font-size: 1.5rem;
    color: var(--primary-dark);
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-md);
    border-bottom: 1px solid var(--border-soft);
}

.lesson-text {
    font-size: 1rem;
    line-height: 2;
    color: var(--text-dark);
}

.lesson-text p {
    margin-bottom: var(--space-lg);
}

.lesson-text strong {
    color: var(--primary-red);
}

.lesson-text .highlight {
    background: #fff5e6;
    padding: 2px 6px;
    border-radius: 3px;
}

/* 音频播放器 */
.audio-player {
    background: var(--bg-cream);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-md);
    padding: var(--space-lg);
    margin: var(--space-xl) 0;
}

.audio-controls {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.play-btn {
    width: 48px;
    height: 48px;
    background: var(--primary-red);
    border: none;
    border-radius: 50%;
    color: white;
    font-size: 1.2rem;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s;
}

.play-btn:hover {
    background: #6b0000;
    transform: scale(1.05);
}

.audio-info {
    flex: 1;
}

.audio-title {
    font-size: 0.9rem;
    font-weight: 500;
    color: var(--primary-dark);
}

.audio-progress {
    height: 4px;
    background: #ddd;
    border-radius: 2px;
    margin-top: var(--space-sm);
    overflow: hidden;
}

.audio-progress-fill {
    height: 100%;
    background: var(--primary-red);
    width: 0%;
    transition: width 0.1s;
}

.audio-time {
    font-size: 0.8rem;
    color: var(--text-light);
    min-width: 80px;
    text-align: right;
}

/* 练习区域 */
.exercise-section {
    margin-top: var(--space-2xl);
    padding-top: var(--space-xl);
    border-top: 2px solid var(--border-soft);
}

.exercise-card {
    background: var(--bg-cream);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-md);
    padding: var(--space-xl);
}

.exercise-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: var(--space-lg);
}

.exercise-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--primary-dark);
}

.exercise-type {
    font-size: 0.75rem;
    color: var(--text-light);
    background: var(--bg-white);
    padding: var(--space-xs) var(--space-sm);
    border-radius: var(--radius-sm);
}

.question {
    font-size: 1rem;
    color: var(--text-dark);
    margin-bottom: var(--space-lg);
    line-height: 1.8;
}

.options {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.option {
    display: flex;
    align-items: center;
    gap: var(--space-md);
    padding: var(--space-md) var(--space-lg);
    background: var(--bg-white);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.2s;
}

.option:hover {
    border-color: var(--primary-red);
    background: #fff;
}

.option.selected {
    border-color: var(--primary-red);
    background: rgba(139,0,0,0.05);
}

.option-letter {
    width: 28px;
    height: 28px;
    background: var(--bg-cream);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-gray);
}

.option.selected .option-letter {
    background: var(--primary-red);
    color: white;
}

.option-text {
    flex: 1;
    font-size: 0.95rem;
}

/* 侧边栏 */
.lesson-sidebar {
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

.sidebar-card {
    background: var(--bg-white);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
}

.sidebar-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--primary-dark);
    margin-bottom: var(--space-md);
    padding-bottom: var(--space-sm);
    border-bottom: 1px solid var(--border-soft);
}

.toc-list {
    list-style: none;
}

.toc-item {
    padding: var(--space-sm) 0;
    border-bottom: 1px dashed var(--border-soft);
}

.toc-item:last-child {
    border-bottom: none;
}

.toc-item a {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-size: 0.85rem;
    color: var(--text-gray);
    text-decoration: none;
    transition: color 0.2s;
}

.toc-item a:hover,
.toc-item.active a {
    color: var(--primary-red);
}

.toc-item .num {
    width: 20px;
    height: 20px;
    background: var(--bg-cream);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 0.7rem;
    font-weight: 600;
}

.toc-item.active .num {
    background: var(--primary-red);
    color: white;
}

/* 笔记区域 */
.notes-area {
    width: 100%;
    min-height: 120px;
    padding: var(--space-md);
    border: 1px solid var(--border-soft);
    border-radius: var(--radius-md);
    font-family: inherit;
    font-size: 0.9rem;
    resize: vertical;
    margin-top: var(--space-sm);
}

.notes-area:focus {
    outline: none;
    border-color: var(--primary-red);
}

/* 响应式 */
@media (max-width: 1024px) {
    .lesson-container {
        grid-template-columns: 1fr;
    }

    .lesson-sidebar {
        flex-direction: row;
        flex-wrap: wrap;
    }

    .sidebar-card {
        flex: 1;
        min-width: 280px;
    }
}

@media (max-width: 768px) {
    .submodules-grid {
        grid-template-columns: 1fr;
    }

    .module-header-inner {
        flex-direction: column;
        text-align: center;
    }
}