/* ===== 全局重置 & 变量 ===== */
:root {
    --primary: #10b981;
    --primary-dark: #059669;
    --primary-light: #6ee7b7;
    --secondary: #34d399;
    --accent: #f59e0b;
    --bg: #f0fdf4;
    --bg-card: #ffffff;
    --text: #1e293b;
    --text-muted: #64748b;
    --border: #e2e8f0;
    --shadow: 0 4px 24px rgba(0,0,0,0.06);
    --shadow-hover: 0 8px 32px rgba(16,185,129,0.18);
    --radius: 16px;
    --radius-sm: 10px;
    --transition: 0.3s cubic-bezier(.4,0,.2,1);
    --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

a {
    text-decoration: none;
    color: inherit;
}

ul {
    list-style: none;
}

img {
    max-width: 100%;
    display: block;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ===== 导航栏 ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(240, 253, 244, 0.75);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-bottom: 1px solid transparent;
    transition: background var(--transition), box-shadow var(--transition);
}

.navbar.scrolled {
    background: rgba(240, 253, 244, 0.92);
    box-shadow: 0 2px 24px rgba(0,0,0,0.06);
}

.nav-container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 68px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-icon {
    width: 36px;
    height: 36px;
}

.logo-text {
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--primary-dark);
}

.nav-links {
    display: flex;
    gap: 32px;
}

.nav-links a {
    font-size: 0.95rem;
    font-weight: 500;
    color: var(--text-muted);
    position: relative;
    padding: 4px 0;
    transition: color var(--transition);
}

.nav-links a::after {
    content: '';
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--primary);
    transition: width var(--transition);
    border-radius: 2px;
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--primary-dark);
}

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

.nav-actions {
    display: flex;
    align-items: center;
    gap: 16px;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 10px 22px;
    border-radius: 50px;
    font-weight: 600;
    font-size: 0.9rem;
    border: none;
    cursor: pointer;
    transition: all var(--transition);
    font-family: var(--font);
}

.btn-sm {
    padding: 6px 16px;
    font-size: 0.82rem;
}

.btn-primary {
    background: var(--primary);
    color: #fff;
    box-shadow: 0 4px 14px rgba(16,185,129,0.35);
}

.btn-primary:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(16,185,129,0.4);
}

.btn-secondary {
    background: transparent;
    color: var(--primary-dark);
    border: 2px solid var(--primary);
}

.btn-secondary:hover {
    background: var(--primary);
    color: #fff;
}

.btn-outline {
    background: transparent;
    color: var(--text-muted);
    border: 1.5px solid var(--border);
}

.btn-outline:hover {
    border-color: var(--primary);
    color: var(--primary-dark);
}

.btn-block {
    width: 100%;
}

.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}

.hamburger span {
    display: block;
    width: 24px;
    height: 2.5px;
    background: var(--text);
    border-radius: 4px;
    transition: all var(--transition);
}

/* ===== Hero ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 100px 0 80px;
    background: linear-gradient(135deg, #ecfdf5 0%, #d1fae5 50%, #a7f3d0 100%);
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -30%;
    right: -20%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(16,185,129,0.12) 0%, transparent 70%);
    border-radius: 50%;
    pointer-events: none;
}

.hero-container {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 60px;
    align-items: center;
}

.hero-content {
    z-index: 1;
}

.hero-logo {
    width: 200px;
    margin-bottom: 24px;
}

.hero h1 {
    font-size: 3rem;
    font-weight: 700;
    line-height: 1.2;
    margin-bottom: 20px;
    color: var(--text);
}

.hero p {
    font-size: 1.15rem;
    color: var(--text-muted);
    max-width: 480px;
    margin-bottom: 36px;
}

.hero-buttons {
    display: flex;
    gap: 16px;
    flex-wrap: wrap;
}

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

.chat-preview {
    background: #fff;
    border-radius: 24px;
    padding: 24px 20px;
    box-shadow: 0 12px 48px rgba(0,0,0,0.08);
    width: 320px;
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.chat-bubble {
    max-width: 75%;
    padding: 12px 16px;
    border-radius: 18px;
    font-size: 0.95rem;
    line-height: 1.4;
    animation: fadeUp 0.6s ease both;
}

.chat-bubble:nth-child(1) { animation-delay: 0.1s; }
.chat-bubble:nth-child(2) { animation-delay: 0.3s; }
.chat-bubble:nth-child(3) { animation-delay: 0.5s; }

.chat-bubble.incoming {
    align-self: flex-start;
    background: #f1f5f9;
    color: var(--text);
    border-bottom-left-radius: 4px;
}

.chat-bubble.outgoing {
    align-self: flex-end;
    background: var(--primary);
    color: #fff;
    border-bottom-right-radius: 4px;
}

.typing-indicator {
    display: flex;
    align-items: center;
    gap: 5px;
    padding: 8px 12px;
    align-self: flex-start;
    background: #f1f5f9;
    border-radius: 18px;
}

.typing-indicator span {
    width: 8px;
    height: 8px;
    background: var(--text-muted);
    border-radius: 50%;
    animation: typing 1.4s infinite ease-in-out;
}

.typing-indicator span:nth-child(2) { animation-delay: 0.2s; }
.typing-indicator span:nth-child(3) { animation-delay: 0.4s; }

@keyframes typing {
    0%, 60%, 100% { opacity: 0.3; transform: translateY(0); }
    30% { opacity: 1; transform: translateY(-4px); }
}

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ===== Section Header ===== */
.section-header {
    text-align: center;
    margin-bottom: 48px;
}

.section-header h2 {
    font-size: 2.2rem;
    font-weight: 700;
    margin-bottom: 12px;
    color: var(--text);
}

.section-header p {
    font-size: 1.05rem;
    color: var(--text-muted);
}

/* ===== Features ===== */
.features {
    padding: 100px 0;
    background: #ffffff;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
    gap: 28px;
}

.feature-card {
    background: var(--bg-card);
    border-radius: var(--radius);
    padding: 32px 24px;
    box-shadow: var(--shadow);
    transition: all var(--transition);
    border: 1px solid var(--border);
    text-align: center;
}

.feature-card:hover {
    transform: translateY(-6px);
    box-shadow: var(--shadow-hover);
    border-color: var(--primary-light);
}

.feature-icon {
    width: 56px;
    height: 56px;
    border-radius: 16px;
    background: linear-gradient(135deg, var(--primary-light), var(--primary));
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 16px;
    font-size: 1.6rem;
    color: #fff;
}

.feature-card h3 {
    font-size: 1.15rem;
    margin-bottom: 10px;
}

.feature-card p {
    font-size: 0.92rem;
    color: var(--text-muted);
}

/* ===== Updates ===== */
.updates {
    padding: 100px 0;
    background: var(--bg);
}

.updates-list {
    display: flex;
    flex-direction: column;
    gap: 20px;
    max-width: 800px;
    margin: 0 auto;
}

.update-item {
    background: #fff;
    border-radius: var(--radius);
    padding: 24px 28px;
    box-shadow: var(--shadow);
    border-left: 4px solid var(--primary);
    transition: all var(--transition);
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 20px;
    flex-wrap: wrap;
}

.update-item:hover {
    box-shadow: var(--shadow-hover);
    transform: translateX(4px);
}

.update-content h4 {
    font-size: 1.05rem;
    margin-bottom: 6px;
}

.update-content p {
    font-size: 0.9rem;
    color: var(--text-muted);
}

.update-tag {
    background: var(--primary-light);
    color: var(--primary-dark);
    padding: 4px 14px;
    border-radius: 50px;
    font-size: 0.78rem;
    font-weight: 600;
    white-space: nowrap;
}

/* ===== About ===== */
.about {
    padding: 100px 0;
    background: #ffffff;
}

.about-content {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 48px;
    align-items: center;
}

.about-text p {
    color: var(--text-muted);
    margin-bottom: 16px;
    font-size: 1rem;
    line-height: 1.7;
}

.about-stats {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 20px;
}

.stat {
    text-align: center;
    background: var(--bg);
    padding: 28px 16px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
}

.stat-number {
    display: block;
    font-size: 1.8rem;
    font-weight: 700;
    color: var(--primary-dark);
}

.stat-label {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 4px;
}

/* ===== Contact ===== */
.contact {
    padding: 100px 0;
    background: var(--bg);
}

.contact-form-wrapper {
    max-width: 520px;
    margin: 0 auto;
}

.contact-form {
    display: flex;
    flex-direction: column;
    gap: 18px;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 14px 18px;
    border-radius: var(--radius-sm);
    border: 1.5px solid var(--border);
    font-size: 0.95rem;
    font-family: var(--font);
    background: #fff;
    transition: border-color var(--transition), box-shadow var(--transition);
    outline: none;
}

.form-group input:focus,
.form-group textarea:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 4px rgba(16,185,129,0.12);
}

/* ===== Footer ===== */
.footer {
    background: #1e293b;
    color: #cbd5e1;
    padding: 60px 0 20px;
}

.footer-container {
    display: grid;
    grid-template-columns: 1.5fr 2fr;
    gap: 60px;
    margin-bottom: 40px;
}

.footer-logo {
    width: 160px;
    margin-bottom: 16px;
}

.footer-brand p {
    font-size: 0.9rem;
    line-height: 1.6;
}

.footer-links {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}

.footer-col h4 {
    color: #fff;
    margin-bottom: 16px;
    font-size: 1rem;
}

.footer-col a {
    display: block;
    color: #94a3b8;
    margin-bottom: 10px;
    font-size: 0.9rem;
    transition: color var(--transition);
}

.footer-col a:hover {
    color: var(--primary-light);
}

.footer-bottom {
    border-top: 1px solid #334155;
    padding-top: 20px;
    text-align: center;
    font-size: 0.85rem;
    color: #64748b;
}

/* ===== 响应式 ===== */
@media (max-width: 992px) {
    .hero-container {
        grid-template-columns: 1fr;
        text-align: center;
    }
    .hero-content {
        order: 1;
    }
    .hero-visual {
        order: 0;
        justify-content: center;
    }
    .hero p {
        margin-left: auto;
        margin-right: auto;
    }
    .hero-buttons {
        justify-content: center;
    }
    .hero h1 {
        font-size: 2.4rem;
    }
    .about-content {
        grid-template-columns: 1fr;
    }
    .footer-container {
        grid-template-columns: 1fr;
        gap: 40px;
    }
}

@media (max-width: 768px) {
    .nav-links {
        position: fixed;
        top: 68px;
        left: 0;
        right: 0;
        background: rgba(240, 253, 244, 0.98);
        backdrop-filter: blur(16px);
        flex-direction: column;
        gap: 0;
        padding: 16px 24px;
        box-shadow: 0 8px 32px rgba(0,0,0,0.08);
        transform: translateY(-120%);
        transition: transform 0.4s ease;
        border-bottom: 1px solid var(--border);
    }
    .nav-links.open {
        transform: translateY(0);
    }
    .nav-links a {
        padding: 12px 0;
        border-bottom: 1px solid var(--border);
    }
    .nav-links a:last-child {
        border-bottom: none;
    }
    .hamburger {
        display: flex;
    }
    .hamburger.active span:nth-child(1) {
        transform: rotate(45deg) translate(5px, 5px);
    }
    .hamburger.active span:nth-child(2) {
        opacity: 0;
    }
    .hamburger.active span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }
    .hero h1 {
        font-size: 2rem;
    }
    .hero-logo {
        width: 160px;
    }
    .section-header h2 {
        font-size: 1.8rem;
    }
    .features-grid {
        grid-template-columns: 1fr;
    }
    .about-stats {
        grid-template-columns: 1fr;
    }
    .footer-links {
        grid-template-columns: 1fr;
    }
    .chat-preview {
        width: 260px;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }
    .hero h1 {
        font-size: 1.6rem;
    }
    .hero p {
        font-size: 1rem;
    }
    .hero-buttons {
        flex-direction: column;
        align-items: stretch;
    }
    .nav-logo .logo-text {
        display: none;
    }
}