/* ===================================================================
   Lanmao Space — Apple-Inspired Design System
   =================================================================== */

/* ===== CSS Custom Properties ===== */
:root {
    --font-system: -apple-system, BlinkMacSystemFont, 'SF Pro Display', 'SF Pro Text',
                   'Helvetica Neue', 'PingFang SC', 'Microsoft YaHei', 'Segoe UI', sans-serif;
    --font-mono: 'SF Mono', 'Fira Code', 'Courier New', monospace;

    --white: #ffffff;
    --off-white: #fbfbfd;
    --gray-50: #f5f5f7;
    --gray-100: #e8e8ed;
    --gray-200: #d2d2d7;
    --gray-400: #86868b;
    --gray-600: #6e6e73;
    --gray-800: #424245;
    --dark: #1d1d1f;
    --pure-black: #000000;

    --blue: #0071e3;
    --blue-hover: #0077ed;

    --transition-fast: 0.2s cubic-bezier(0.25, 0.1, 0.25, 1);
    --transition-base: 0.36s cubic-bezier(0.25, 0.1, 0.25, 1);
    --transition-slow: 0.5s cubic-bezier(0.25, 0.1, 0.25, 1);

    --container-width: 980px;
    --section-padding: 160px;
    --card-radius: 22px;
    --ease-out: cubic-bezier(0.22, 1, 0.36, 1);
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
    scroll-padding-top: 52px;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-system);
    background: var(--white);
    color: var(--dark);
    line-height: 1.47059;
    font-weight: 400;
    letter-spacing: -0.022em;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    overflow-x: hidden;
}

.skip-link {
    position: absolute;
    top: -100%;
    left: 16px;
    z-index: 10000;
    padding: 12px 24px;
    background: var(--blue);
    color: var(--white);
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    text-decoration: none;
    transition: top var(--transition-fast);
}

.skip-link:focus {
    top: 16px;
}

a {
    text-decoration: none;
    color: inherit;
    transition: color var(--transition-fast);
}

img { max-width: 100%; }

button {
    cursor: pointer;
    border: none;
    outline: none;
    background: none;
    font-family: var(--font-system);
}

.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 22px;
}

/* ===== Selection ===== */
::selection {
    background: rgba(0, 113, 227, 0.15);
    color: var(--dark);
}

/* ===== Navbar — Frosted Glass ===== */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 9999;
    background: rgba(251, 251, 253, 0.72);
    backdrop-filter: saturate(180%) blur(20px);
    -webkit-backdrop-filter: saturate(180%) blur(20px);
    border-bottom: 0.5px solid rgba(0, 0, 0, 0.07);
    transition: background var(--transition-base);
}

.navbar.scrolled {
    background: rgba(251, 251, 253, 0.92);
}

.nav-container {
    max-width: 1024px;
    margin: 0 auto;
    padding: 0 22px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 52px;
}

.nav-logo {
    display: flex;
    align-items: center;
    gap: 8px;
    font-weight: 600;
    font-size: 0.95rem;
    color: var(--dark);
    letter-spacing: -0.01em;
}

.logo-icon {
    font-size: 1.35rem;
    line-height: 1;
}

.logo-text {
    font-weight: 600;
}

.nav-links {
    display: flex;
    gap: 4px;
}

.nav-link {
    padding: 6px 14px;
    border-radius: 980px;
    font-size: 0.82rem;
    font-weight: 400;
    color: var(--gray-600);
    transition: color var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
    letter-spacing: 0;
}

.nav-link:hover {
    color: var(--dark);
    background: rgba(0, 0, 0, 0.04);
}

.nav-link.active {
    color: var(--dark);
    font-weight: 500;
}

.nav-toggle {
    display: none;
    flex-direction: column;
    gap: 5px;
    padding: 4px;
}

.nav-toggle span {
    display: block;
    width: 18px;
    height: 1.5px;
    background: var(--dark);
    border-radius: 2px;
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
    transform-origin: center;
}

/* ===== Hero Section ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
    background: var(--off-white);
    overflow: hidden;
    padding: 52px 22px 0;
}

.hero-bg {
    position: absolute;
    inset: 0;
    pointer-events: none;
    overflow: hidden;
}

.hero-orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(64px);
    opacity: 0.22;
    animation: orbFloat 28s ease-in-out infinite;
}

.orb-1 {
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, #a78bfa 0%, transparent 70%);
    top: -10%;
    right: -10%;
    animation-delay: 0s;
}

.orb-2 {
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, #60a5fa 0%, transparent 70%);
    bottom: -15%;
    left: -10%;
    animation-delay: -7s;
}

.orb-3 {
    width: 400px;
    height: 400px;
    background: radial-gradient(circle, #f472b6 0%, transparent 70%);
    top: 50%;
    left: 50%;
    margin: -200px 0 0 -200px;
    animation-delay: -14s;
}

@keyframes orbFloat {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(30px, -30px) scale(1.05); }
    66% { transform: translate(-20px, 20px) scale(0.95); }
}

.hero-content {
    text-align: center;
    position: relative;
    z-index: 1;
    max-width: 780px;
}

.hero-eyebrow {
    font-size: 1.125rem;
    font-weight: 500;
    color: var(--gray-600);
    letter-spacing: 0.02em;
    margin-bottom: 12px;
    opacity: 0;
    transform: translateY(20px);
    animation: heroFadeUp 0.85s var(--ease-out) forwards 0.2s;
}

.hero-title {
    font-size: clamp(48px, 8vw, 80px);
    font-weight: 700;
    line-height: 1.05;
    letter-spacing: -0.045em;
    margin-bottom: 24px;
    color: var(--dark);
    opacity: 0;
    transform: translateY(20px);
    animation: heroFadeUp 0.85s var(--ease-out) forwards 0.28s;
}

.gradient-text {
    background: linear-gradient(135deg, #6366f1 0%, #a855f7 35%, #ec4899 70%, #f43f5e 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.3125rem;
    font-weight: 400;
    color: var(--gray-600);
    line-height: 1.5;
    margin-bottom: 48px;
    letter-spacing: 0.012em;
    opacity: 0;
    transform: translateY(20px);
    animation: heroFadeUp 0.85s var(--ease-out) forwards 0.36s;
}

.hero-stats {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 40px;
    margin-bottom: 56px;
    opacity: 0;
    transform: translateY(20px);
    animation: heroFadeUp 0.85s var(--ease-out) forwards 0.44s;
}

.stat-item {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    letter-spacing: -0.04em;
    color: var(--dark);
    line-height: 1.1;
}

.stat-label {
    display: block;
    font-size: 0.8125rem;
    color: var(--gray-400);
    margin-top: 4px;
    font-weight: 400;
    letter-spacing: 0.01em;
}

.stat-divider {
    width: 1px;
    height: 40px;
    background: var(--gray-200);
}

.hero-cta {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    font-size: 1.0625rem;
    font-weight: 400;
    color: var(--blue);
    opacity: 0;
    transform: translateY(20px);
    animation: heroFadeUp 0.85s var(--ease-out) forwards 0.52s;
    transition: gap var(--transition-fast);
}

.hero-cta:hover {
    gap: 12px;
    color: var(--blue-hover);
}

.hero-cta svg {
    transition: transform 0.4s var(--ease-out);
}

@keyframes heroFadeUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes scrollBounce {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(6px); }
}

/* ===== Section Layout ===== */
.section {
    padding: var(--section-padding) 0;
}

.section-light {
    background: var(--white);
}

.section-dark {
    background: var(--dark);
    color: var(--gray-200);
}

.section-dark .section-title {
    color: var(--gray-50);
}

.section-dark .section-desc {
    color: var(--gray-400);
}

.section-header {
    text-align: center;
    margin-bottom: 64px;
}

.section-title {
    font-size: clamp(32px, 5vw, 48px);
    font-weight: 700;
    letter-spacing: -0.04em;
    line-height: 1.1;
    margin-bottom: 12px;
    color: var(--dark);
}

.section-desc {
    font-size: 1.0625rem;
    color: var(--gray-600);
    font-weight: 400;
    letter-spacing: 0.012em;
}

/* ===== Filter Tabs (Pill Buttons) ===== */
.filter-tabs {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-bottom: 48px;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 8px 22px;
    border-radius: 980px;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--gray-600);
    background: transparent;
    border: none;
    transition: color var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
    letter-spacing: 0;
}

.filter-btn:hover {
    color: var(--dark);
    background: rgba(0, 0, 0, 0.04);
}

.filter-btn.active {
    background: var(--dark);
    color: var(--white);
}

/* ===== Books Grid ===== */
.books-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 20px;
}

.book-card {
    background: var(--white);
    border-radius: var(--card-radius);
    overflow: hidden;
    display: flex;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
    border: 0.5px solid rgba(0, 0, 0, 0.06);
}

.book-card:hover {
    transform: scale(1.02);
    box-shadow: 0 8px 40px rgba(0, 0, 0, 0.1);
}

.book-card.hidden {
    display: none;
}

.book-cover {
    width: 100px;
    min-height: 160px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.book-emoji {
    font-size: 2.5rem;
    filter: drop-shadow(0 2px 8px rgba(0, 0, 0, 0.15));
}

.book-info {
    padding: 22px;
    flex: 1;
}

.book-title {
    font-size: 1.0625rem;
    font-weight: 600;
    letter-spacing: -0.02em;
    margin-bottom: 4px;
}

.book-author {
    font-size: 0.8125rem;
    color: var(--gray-600);
    margin-bottom: 10px;
}

.book-rating {
    font-size: 0.75rem;
    margin-bottom: 10px;
}

.book-tag {
    display: inline-block;
    font-size: 0.6875rem;
    padding: 3px 10px;
    border-radius: 980px;
    font-weight: 500;
    margin-bottom: 10px;
    letter-spacing: 0.01em;
}

.tag-reading { background: #fef3c7; color: #92400e; }
.tag-finished { background: #d1fae5; color: #065f46; }
.tag-wishlist { background: #ede9fe; color: #5b21b6; }

.book-note {
    font-size: 0.8125rem;
    color: var(--gray-600);
    line-height: 1.5;
    font-style: italic;
}

/* ===== Music & Movies ===== */
.media-tabs {
    display: flex;
    justify-content: center;
    gap: 8px;
    margin-bottom: 48px;
}

.media-tab {
    padding: 10px 26px;
    border-radius: 980px;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--gray-400);
    background: transparent;
    border: 1px solid rgba(255, 255, 255, 0.15);
    transition: color var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
}

.media-tab:hover {
    color: var(--white);
    border-color: rgba(255, 255, 255, 0.3);
}

.media-tab.active {
    background: var(--white);
    color: var(--dark);
    border-color: var(--white);
}

.media-content {
    display: none;
    animation: contentFadeIn 0.32s var(--ease-out);
}

.media-content.active {
    display: block;
}

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

.playlist-header {
    text-align: center;
    margin-bottom: 36px;
}

.playlist-header h3 {
    font-size: 1.375rem;
    font-weight: 600;
    margin-bottom: 8px;
    letter-spacing: -0.02em;
    color: var(--gray-50);
}

.playlist-desc {
    font-size: 0.9375rem;
    color: var(--gray-400);
}

.playlist-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 12px;
}

.song-card {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 14px 18px;
    background: rgba(255, 255, 255, 0.06);
    border-radius: 14px;
    border: 0.5px solid rgba(255, 255, 255, 0.08);
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
}

.song-card:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: translateY(-2px);
}

.song-cover {
    width: 48px;
    height: 48px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    flex-shrink: 0;
}

.song-info {
    flex: 1;
    min-width: 0;
}

.song-info h4 {
    font-size: 0.9375rem;
    font-weight: 600;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    color: var(--gray-50);
    letter-spacing: -0.01em;
}

.song-info p {
    font-size: 0.8125rem;
    color: var(--gray-400);
}

.song-tag {
    font-size: 0.6875rem;
    padding: 3px 10px;
    border-radius: 980px;
    background: rgba(255, 255, 255, 0.08);
    color: var(--gray-200);
    font-weight: 500;
    white-space: nowrap;
}

.movie-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 20px;
}

.movie-card {
    background: rgba(255, 255, 255, 0.06);
    border-radius: var(--card-radius);
    overflow: hidden;
    border: 0.5px solid rgba(255, 255, 255, 0.08);
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
}

.movie-card:hover {
    transform: scale(1.03);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.25);
}

.movie-poster {
    height: 180px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 3.5rem;
}

.movie-info {
    padding: 20px;
}

.movie-info h4 {
    font-size: 1.0625rem;
    font-weight: 600;
    margin-bottom: 4px;
    letter-spacing: -0.02em;
    color: var(--gray-50);
}

.movie-genre {
    font-size: 0.8125rem;
    color: var(--gray-400);
    margin-bottom: 8px;
}

.movie-rating {
    font-size: 0.875rem;
    color: #fbbf24;
    font-weight: 600;
    margin-bottom: 8px;
}

.movie-comment {
    font-size: 0.8125rem;
    color: var(--gray-400);
    font-style: italic;
    line-height: 1.5;
}

/* ===== Friends ===== */
.friends-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 16px;
    margin-bottom: 40px;
}

.friend-card {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 22px;
    background: var(--white);
    border-radius: var(--card-radius);
    border: 0.5px solid rgba(0, 0, 0, 0.06);
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
}

.friend-card:hover {
    transform: scale(1.03);
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.1);
}

.friend-avatar {
    width: 52px;
    height: 52px;
    border-radius: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    flex-shrink: 0;
}

.friend-info h4 {
    font-size: 0.9375rem;
    font-weight: 600;
    margin-bottom: 2px;
    letter-spacing: -0.01em;
}

.friend-info p {
    font-size: 0.8125rem;
    color: var(--gray-600);
}

.friend-apply {
    text-align: center;
    padding: 24px;
    background: var(--gray-50);
    border-radius: 14px;
    font-size: 0.9375rem;
    color: var(--gray-600);
}

/* ===== Toolbox ===== */
.tools-category {
    margin-bottom: 56px;
}

.tools-category:last-child {
    margin-bottom: 0;
}

.category-title {
    font-size: 1.1875rem;
    font-weight: 600;
    margin-bottom: 20px;
    letter-spacing: -0.02em;
    color: var(--gray-50);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 12px;
}

.tool-card {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 16px 18px;
    background: rgba(255, 255, 255, 0.06);
    border-radius: 14px;
    border: 0.5px solid rgba(255, 255, 255, 0.08);
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
}

.tool-card:hover {
    background: rgba(255, 255, 255, 0.1);
    transform: scale(1.02);
}

.tool-icon {
    width: 42px;
    height: 42px;
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.125rem;
    flex-shrink: 0;
    color: white;
}

.tool-info h4 {
    font-size: 0.9375rem;
    font-weight: 600;
    margin-bottom: 2px;
    letter-spacing: -0.01em;
    color: var(--gray-50);
}

.tool-info p {
    font-size: 0.8125rem;
    color: var(--gray-400);
}

/* ===== Contact & Guestbook ===== */
.contact-wrapper {
    display: grid;
    grid-template-columns: 1fr 340px;
    gap: 32px;
    align-items: start;
}

.guestbook {
    background: var(--white);
    border-radius: var(--card-radius);
    padding: 36px;
    border: 0.5px solid rgba(0, 0, 0, 0.06);
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
}

.message-form {
    margin-bottom: 32px;
}

.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

.form-group {
    margin-bottom: 16px;
}

.form-group label {
    display: block;
    font-size: 0.8125rem;
    font-weight: 500;
    margin-bottom: 6px;
    color: var(--gray-600);
    letter-spacing: 0;
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid var(--gray-200);
    border-radius: 10px;
    font-family: var(--font-system);
    font-size: 0.9375rem;
    color: var(--dark);
    background: var(--gray-50);
    transition: color var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
    outline: none;
    letter-spacing: -0.01em;
}

.form-group input:focus,
.form-group textarea:focus {
    border-color: var(--blue);
    box-shadow: 0 0 0 3px rgba(0, 113, 227, 0.12);
    background: var(--white);
}

.form-group textarea {
    resize: vertical;
    min-height: 100px;
}

.submit-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 28px;
    background: var(--blue);
    color: white;
    border-radius: 980px;
    font-size: 0.9375rem;
    font-weight: 500;
    transition: color var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
    border: none;
    letter-spacing: 0;
}

.submit-btn:hover {
    background: var(--blue-hover);
    transform: scale(1.04);
}

.btn-icon {
    font-size: 1rem;
}

.messages-list {
    border-top: 0.5px solid var(--gray-100);
    padding-top: 24px;
}

.guestbook-note,
.guestbook-status,
.guestbook-empty {
    color: var(--gray-600);
    font-size: 0.875rem;
    line-height: 1.7;
}

.guestbook-note {
    margin-bottom: 8px;
}

.guestbook-status {
    min-height: 1.5em;
    margin-bottom: 8px;
}

.guestbook-status:empty {
    display: none;
}

.guestbook-empty {
    padding: 18px 0;
    text-align: center;
}

.message-item {
    display: flex;
    gap: 14px;
    padding: 18px 0;
    border-bottom: 0.5px solid var(--gray-100);
}

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

.message-avatar {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    flex-shrink: 0;
}

.message-content {
    flex: 1;
}

.message-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 4px;
}

.message-name {
    font-weight: 600;
    font-size: 0.875rem;
    letter-spacing: -0.01em;
}

.message-time {
    font-size: 0.75rem;
    color: var(--gray-400);
}

.message-content p {
    font-size: 0.875rem;
    color: var(--gray-600);
    line-height: 1.5;
}

.contact-card {
    background: var(--white);
    border-radius: var(--card-radius);
    padding: 32px;
    border: 0.5px solid rgba(0, 0, 0, 0.06);
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.04);
    position: sticky;
    top: 72px;
}

.contact-card h3 {
    font-size: 1.1875rem;
    font-weight: 600;
    margin-bottom: 24px;
    letter-spacing: -0.02em;
}

.contact-links {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 28px;
}

.contact-link {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 14px;
    border-radius: 12px;
    transition: color var(--transition-fast), background-color var(--transition-fast), border-color var(--transition-fast), box-shadow var(--transition-fast), transform var(--transition-fast);
    background: var(--gray-50);
}

.contact-link:hover {
    background: var(--gray-100);
    transform: translateX(4px);
}

.contact-icon {
    font-size: 1.25rem;
}

.contact-label {
    display: block;
    font-size: 0.6875rem;
    color: var(--gray-400);
    letter-spacing: 0.02em;
    text-transform: uppercase;
}

.contact-value {
    font-size: 0.8125rem;
    font-weight: 500;
    letter-spacing: -0.01em;
}

.contact-qrcode {
    text-align: center;
}

.qr-placeholder {
    width: 120px;
    height: 120px;
    margin: 0 auto;
    background: var(--gray-50);
    border-radius: 14px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border: 1.5px dashed var(--gray-200);
}

.qr-placeholder span {
    font-size: 2rem;
    margin-bottom: 4px;
}

.qr-placeholder p {
    font-size: 0.6875rem;
    color: var(--gray-400);
}

/* ===== Footer ===== */
.footer {
    background: var(--dark);
    color: var(--gray-400);
    padding: 64px 0;
}

.footer-content {
    text-align: center;
}

.footer-logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    font-size: 1.0625rem;
    font-weight: 600;
    color: var(--gray-50);
    margin-bottom: 16px;
}

.footer-logo span:first-child {
    font-size: 1.4rem;
}

.footer-text {
    font-size: 0.8125rem;
    margin-bottom: 8px;
    color: var(--gray-400);
}

.footer-quote {
    font-size: 0.8125rem;
    font-style: italic;
    color: var(--gray-600);
}

/* ===== Back to Top ===== */
.back-to-top {
    position: fixed;
    bottom: 32px;
    right: 32px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: rgba(29, 29, 31, 0.72);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    color: var(--white);
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.15);
    transition: transform 0.45s var(--ease-out), box-shadow 0.45s var(--ease-out), background-color var(--transition-base), opacity var(--transition-base), visibility var(--transition-base);
    opacity: 0;
    visibility: hidden;
    transform: translateY(16px);
    z-index: 999;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    background: rgba(29, 29, 31, 0.92);
    transform: translateY(-3px);
}

/* ===== Scroll Fade-Up Animations ===== */
.fade-up {
    opacity: 1;
    transform: none;
}

/* 仅在观察器就绪后隐藏元素；脚本不可用时仍可阅读。 */
.fade-up.reveal-pending {
    opacity: 0;
    transform: translateY(18px);
    transition: opacity 0.7s var(--ease-out), transform 0.7s var(--ease-out);
}

.fade-up.reveal-pending.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    :root {
        --section-padding: 100px;
    }

    .nav-links {
        position: fixed;
        top: 52px;
        left: 0;
        right: 0;
        background: rgba(251, 251, 253, 0.96);
        backdrop-filter: saturate(180%) blur(20px);
        -webkit-backdrop-filter: saturate(180%) blur(20px);
        padding: 12px 22px 16px;
        flex-direction: column;
        gap: 2px;
        border-bottom: 0.5px solid rgba(0, 0, 0, 0.07);
        opacity: 0;
        visibility: hidden;
        pointer-events: none;
        transform: translateY(-8px);
        transition: opacity 0.24s ease, transform 0.32s var(--ease-out), visibility 0.24s;
    }

    .nav-links.open {
        opacity: 1;
        visibility: visible;
        pointer-events: auto;
        transform: translateY(0);
    }

    .nav-toggle {
        display: flex;
    }

    .nav-toggle.open span:nth-child(1) {
        transform: rotate(45deg) translate(4px, 4px);
    }
    .nav-toggle.open span:nth-child(2) {
        opacity: 0;
    }
    .nav-toggle.open span:nth-child(3) {
        transform: rotate(-45deg) translate(5px, -5px);
    }

    .hero-title {
        font-size: clamp(36px, 10vw, 56px);
    }

    .hero-stats {
        gap: 20px;
    }

    .stat-number {
        font-size: 1.75rem;
    }

    .stat-divider {
        height: 28px;
    }

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

    .contact-wrapper {
        grid-template-columns: 1fr;
    }

    .form-row {
        grid-template-columns: 1fr;
    }

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

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

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

    .movie-grid {
        grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    }

    .contact-card {
        position: static;
    }
}

@media (max-width: 480px) {
    :root {
        --section-padding: 80px;
    }

    .hero-subtitle {
        font-size: 1.0625rem;
    }

    .section-title {
        font-size: 28px;
    }
}


/* ===== 柔和质感与交互细节 ===== */
.hero { min-height: 100svh; padding-bottom: 40px; }
.hero-title { line-height: 1.12; }
.hero-subtitle { line-height: 1.75; }
.section-title { line-height: 1.25; }
.section-desc { line-height: 1.65; }
.section-light { background: #fbfbfd; }
.section-dark { background: linear-gradient(160deg, #202126, #1d1d1f 65%); }
.navbar { transition: background-color 0.35s ease, box-shadow 0.35s ease; }
.navbar.scrolled { box-shadow: 0 4px 24px rgba(29, 29, 31, 0.035); }
.book-card, .friend-card, .guestbook, .contact-card {
    box-shadow: 0 4px 24px rgba(29, 29, 31, 0.035);
    border-color: rgba(29, 29, 31, 0.045);
}
.book-cover, .movie-poster { box-shadow: inset 0 0 0 1000px rgba(255, 255, 255, 0.08); }
.book-info, .friend-info, .tool-info, .message-content { min-width: 0; overflow-wrap: anywhere; }
.stat-number { font-variant-numeric: tabular-nums; }
.song-card { min-width: 0; }
.song-info p { overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.filter-btn, .media-tab, .nav-toggle { min-height: 44px; min-width: 44px; }
.nav-toggle { align-items: center; justify-content: center; }
.book-card:hover, .friend-card:hover, .movie-card:hover, .tool-card:hover,
.song-card:hover, .submit-btn:hover, .contact-link:hover { transform: none; }
:where(a, button, input, textarea, [tabindex]):focus-visible {
    outline: 3px solid #2997ff;
    outline-offset: 5px;
}
.message-content p { white-space: pre-wrap; }
@media (hover: hover) and (pointer: fine) {
    .book-card:hover, .friend-card:hover, .movie-card:hover {
        transform: translateY(-4px);
        box-shadow: 0 12px 32px rgba(0, 0, 0, 0.085);
    }
    .tool-card:hover, .song-card:hover { transform: translateY(-2px); }
    .hero-cta:hover svg { transform: translateY(3px); }
    .submit-btn:hover { transform: translateY(-1px); }
}
@media (max-width: 768px) {
    .hero-orb { animation: none; filter: blur(48px); }
    .nav-links { max-height: calc(100svh - 52px); overflow-y: auto; }
    .nav-link { padding: 13px 16px; }
    .hero-stats { gap: 22px; }
    .section-header { margin-bottom: 40px; }
}
@media (max-width: 480px) {
    .hero { padding-top: 100px; padding-bottom: 56px; }
    .hero-title { font-size: clamp(42px, 12vw, 56px); }
    .hero-subtitle { margin-bottom: 36px; }
    .hero-stats { margin-bottom: 40px; }
    .book-cover { width: 76px; }
    .book-info { padding: 18px 16px; }
    .guestbook, .contact-card { padding: 24px 20px; }
    .message-header { flex-wrap: wrap; gap: 4px 12px; }
    .back-to-top { right: 18px; bottom: 20px; }
}
@media (prefers-reduced-motion: reduce) {
    html { scroll-behavior: auto; }
    *, *::before, *::after { animation: none !important; transition: none !important; }
    .fade-up, .fade-up.reveal-pending, .hero-eyebrow, .hero-title,
    .hero-subtitle, .hero-stats, .hero-cta { opacity: 1; transform: none; }
}