/* EduBuddy AI学伴官网 - 明亮清新风格 */

/* 基础变量 */
:root {
    --bg-primary: #ffffff;
    --bg-secondary: #f8f9fa;
    --bg-card: #ffffff;
    --accent-primary: #4f46e5;
    --accent-secondary: #06b6d4;
    --accent-gradient: linear-gradient(135deg, #4f46e5 0%, #06b6d4 100%);
    --text-primary: #1f2937;
    --text-secondary: #4b5563;
    --text-muted: #9ca3af;
    --border-color: #e5e7eb;
    --card-shadow: 0 4px 20px rgba(79, 70, 229, 0.1);
}

/* 基础样式 */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'PingFang SC', 'Source Han Sans CN', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

/* Header */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
}

.nav {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo img {
    height: 40px;
}

.nav-links {
    display: flex;
    gap: 2rem;
    list-style: none;
}

.nav-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.95rem;
    transition: color 0.3s ease;
    position: relative;
}

.nav-links a:hover {
    color: var(--accent-primary);
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -4px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--accent-gradient);
    transition: width 0.3s ease;
}

.nav-links a:hover::after {
    width: 100%;
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    padding-top: 80px;
    overflow: hidden;
}

.hero-gradient {
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: radial-gradient(ellipse at 30% 20%, rgba(79, 70, 229, 0.08) 0%, transparent 50%),
                radial-gradient(ellipse at 70% 80%, rgba(6, 182, 212, 0.06) 0%, transparent 50%);
    z-index: 0;
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
    z-index: 1;
}

.hero-text {
    animation: fadeInUp 0.8s ease;
}

.hero-title {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 1rem;
    color: var(--accent-primary);
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    letter-spacing: 0.1em;
}

.hero-desc {
    font-size: 1.1rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
    max-width: 400px;
}

.btn-primary {
    display: inline-block;
    padding: 1rem 2rem;
    background: var(--accent-gradient);
    color: white;
    text-decoration: none;
    border-radius: 8px;
    font-weight: 500;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(79, 70, 229, 0.3);
}

.hero-image {
    animation: fadeInRight 0.8s ease;
}

.hero-image img {
    width: 100%;
    max-width: 500px;
    filter: drop-shadow(0 20px 40px rgba(79, 70, 229, 0.2));
    animation: float 6s ease-in-out infinite;
}

/* Features Section */
.features {
    padding: 100px 0;
    background: var(--bg-secondary);
}

.section-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

.section-title {
    text-align: center;
    font-size: 2.5rem;
    margin-bottom: 3rem;
    color: var(--accent-primary);
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 2rem;
}

.feature-card {
    background: var(--bg-card);
    padding: 2rem;
    border-radius: 16px;
    border: 1px solid var(--border-color);
    transition: transform 0.3s ease, box-shadow 0.3s ease;
    position: relative;
    overflow: hidden;
}

.feature-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--accent-gradient);
}

.feature-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--card-shadow);
}

.feature-icon {
    width: 60px;
    height: 60px;
    margin-bottom: 1.5rem;
    color: var(--accent-primary);
}

.feature-icon svg {
    width: 100%;
    height: 100%;
}

.feature-card h3 {
    font-size: 1.3rem;
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.feature-card p {
    color: var(--text-secondary);
    margin-bottom: 1rem;
    line-height: 1.7;
}

.feature-list {
    list-style: none;
    margin-top: 1rem;
}

.feature-list li {
    color: var(--text-muted);
    font-size: 0.9rem;
    padding: 0.3rem 0;
    position: relative;
    padding-left: 1rem;
}

.feature-list li::before {
    content: '·';
    position: absolute;
    left: 0;
    color: var(--accent-primary);
}

/* Specs Section */
.specs {
    padding: 100px 0;
    background: var(--bg-primary);
}

.specs-table-wrapper {
    overflow-x: auto;
}

.specs-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--bg-card);
    border-radius: 12px;
    overflow: hidden;
    border: 1px solid var(--border-color);
}

.specs-table th,
.specs-table td {
    padding: 1.2rem 1.5rem;
    text-align: left;
}

.specs-table th {
    background: rgba(79, 70, 229, 0.05);
    color: var(--accent-primary);
    font-weight: 500;
    width: 150px;
    border-right: 1px solid var(--border-color);
}

.specs-table td {
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border-color);
}

.specs-table tr:last-child td {
    border-bottom: none;
}

/* FAQ Section */
.faq {
    padding: 100px 0;
    background: var(--bg-primary);
}

.faq-list {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    background: var(--bg-card);
    margin-bottom: 1rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    overflow: hidden;
    transition: border-color 0.3s ease;
}

.faq-item:hover {
    border-color: var(--accent-primary);
}

.faq-question {
    padding: 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    cursor: pointer;
}

.faq-icon {
    width: 36px;
    height: 36px;
    background: var(--accent-gradient);
    border-radius: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 1rem;
    color: white;
}

.faq-question h3 {
    font-size: 1.1rem;
    color: var(--text-primary);
}

.faq-answer {
    padding: 0 1.5rem 1.5rem 4rem;
}

.faq-answer p {
    color: var(--text-secondary);
    line-height: 1.7;
}

/* Download Section */
.download {
    padding: 100px 0;
    background: var(--bg-secondary);
}

.download-desc {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 2rem;
    font-size: 1.1rem;
}

.download-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
    max-width: 600px;
    margin: 0 auto;
}

.download-card {
    background: var(--bg-card);
    padding: 2rem;
    border-radius: 16px;
    border: 1px solid var(--border-color);
    text-align: center;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.download-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--card-shadow);
}

.download-icon {
    width: 60px;
    height: 60px;
    margin: 0 auto 1rem;
    color: var(--accent-primary);
}

.download-icon svg {
    width: 100%;
    height: 100%;
}

.download-card h3 {
    font-size: 1.2rem;
    margin-bottom: 0.5rem;
    color: var(--text-primary);
}

.download-card p {
    color: var(--text-muted);
    font-size: 0.9rem;
    margin-bottom: 1.5rem;
}

.btn-download {
    display: inline-block;
    padding: 0.8rem 1.5rem;
    background: var(--accent-gradient);
    color: white;
    text-decoration: none;
    border-radius: 8px;
    font-weight: 500;
    transition: transform 0.3s ease, box-shadow 0.3s ease;
}

.btn-download:hover {
    transform: translateY(-2px);
    box-shadow: 0 5px 15px rgba(79, 70, 229, 0.3);
}

/* Footer */
.footer {
    background: var(--bg-primary);
    border-top: 1px solid var(--border-color);
    padding: 60px 0 30px;
}

.footer-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 3rem;
}

.footer-logo {
    height: 50px;
    margin-bottom: 1rem;
}

.footer-tagline {
    color: var(--text-muted);
    font-size: 0.95rem;
}

.footer-info h4 {
    color: var(--text-primary);
    font-size: 1.1rem;
    margin-bottom: 1rem;
}

.footer-info p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.8;
}

.footer-bottom {
    text-align: center;
    padding-top: 2rem;
    margin-top: 2rem;
    border-top: 1px solid var(--border-color);
}

.footer-bottom p {
    color: var(--text-muted);
    font-size: 0.85rem;
}

.footer-links {
    margin-top: 0.5rem;
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    transition: color 0.3s ease;
}

.footer-links a:hover {
    color: var(--accent-primary);
}

.footer-links .separator {
    color: var(--text-muted);
    margin: 0 0.5rem;
}

/* 动画 */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInRight {
    from {
        opacity: 0;
        transform: translateX(30px);
    }
    to {
        opacity: 1;
        transform: translateX(0);
    }
}

@keyframes float {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-20px);
    }
}

/* 响应式设计 */
@media (max-width: 1024px) {
    .hero-content {
        grid-template-columns: 1fr;
        text-align: center;
    }

    .hero-desc {
        max-width: 100%;
    }

    .hero-image img {
        max-width: 400px;
    }

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

    .footer-container {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .nav {
        padding: 1rem;
    }

    .nav-links {
        gap: 1rem;
        font-size: 0.85rem;
    }

    .hero-title {
        font-size: 2.5rem;
    }

    .hero-subtitle {
        font-size: 1.2rem;
    }

    .section-title {
        font-size: 2rem;
    }

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

    .specs-table th {
        width: 100px;
    }

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

    .footer-container {
        gap: 2rem;
    }
}

@media (max-width: 480px) {
    .hero-title {
        font-size: 2rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .nav-links {
        display: none;
    }

    .feature-card {
        padding: 1.5rem;
    }

    .specs-table th,
    .specs-table td {
        padding: 0.8rem;
        font-size: 0.9rem;
    }
}