:root {
    --primary-color: var(--theme-dark, #3b82f6); 
    --primary-hover: var(--theme-light, #2563eb);
    --secondary-color: #64748b;
    --accent-color: var(--theme-gold, #10b981); 
    --bg-color: #f8fafc;
    --card-bg: rgba(255, 255, 255, 0.85);
    --text-main: var(--theme-text, #1e293b);
    --text-muted: #64748b;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-lg: 1rem;
    --radius-md: 0.75rem;
    --card-border: rgba(255, 255, 255, 0.5);
}

.dark-mode {
    --bg-color: #0f172a;
    --card-bg: rgba(30, 41, 59, 0.7);
    --text-main: #f1f5f9;
    --text-muted: #94a3b8;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.4), 0 2px 4px -1px rgba(0, 0, 0, 0.2);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.5), 0 4px 6px -2px rgba(0, 0, 0, 0.3);
    --card-border: rgba(255, 255, 255, 0.1);
}

/* Background Layer Styles */
.background-layer {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    z-index: -10;
    transform: scale(1.02);
    transition: filter 0.5s ease;
}

.background-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(135deg, rgba(203, 213, 225, 0.4), rgba(203, 213, 225, 0.6));
    z-index: -9;
}

.dark-mode .background-overlay {
    background: linear-gradient(135deg, rgba(15, 23, 42, 0.8), rgba(15, 23, 42, 0.9));
}

.dark-mode .background-layer {
    filter: brightness(0.6) saturate(0.8);
}

/* Theme Toggle Button Style */
.theme-toggle {
    position: fixed;
    top: 1.5rem;
    right: 1.5rem;
    z-index: 100;
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    color: var(--text-main);
    width: 44px;
    height: 44px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: var(--shadow-md);
    transition: all 0.3s ease;
}

.theme-toggle:hover {
    transform: rotate(15deg) scale(1.1);
}

.theme-toggle .sun-icon { display: none; }
.theme-toggle .moon-icon { display: block; }

.dark-mode .theme-toggle .sun-icon { display: block; }
.dark-mode .theme-toggle .moon-icon { display: none; }

.dark-mode .qr-placeholder {
    background: #1e293b;
    border-color: #334155;
}

.dark-mode .method-divider {
    background: #334155;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans SC", sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    line-height: 1.625;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

/* Header & Hero */
.hero {
    text-align: center;
    padding: 2rem 1.5rem; /* Adjusted for card enclosure */
}

.hero.card {
    margin-top: 1rem;
}

.avatar-container {
    position: relative;
    display: inline-block;
    margin-bottom: 1.5rem;
}

.avatar {
    width: 120px;
    height: 120px;
    border-radius: 50%;
    border: 4px solid #fff;
    box-shadow: var(--shadow-lg);
}

.status-online {
    position: absolute;
    bottom: 5px;
    right: 15px;
    width: 18px;
    height: 18px;
    background-color: var(--accent-color);
    border: 3px solid #fff;
    border-radius: 50%;
}

.hero h1 {
    font-size: 2.5rem;
    font-weight: 800;
    margin-bottom: 0.5rem;
    background: linear-gradient(135deg, var(--primary-color), var(--accent-color));
    -webkit-background-clip: text;
    background-clip: text;
    -webkit-text-fill-color: transparent;
}

.tagline {
    font-size: 1.125rem;
    color: var(--text-muted);
    margin-bottom: 2rem;
}

.hero-actions {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

/* Common Card Styles */
.card {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: var(--radius-lg);
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-md);
    transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.card h3 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

/* Announcement Card */
.announcement {
    display: flex;
    gap: 1.25rem;
    align-items: center;
}

.card-icon {
    flex-shrink: 0;
    width: 48px;
    height: 48px;
    background: rgba(59, 130, 246, 0.1);
    color: var(--primary-color);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.announcement-content h3 {
    font-size: 1rem;
    margin-bottom: 0.25rem;
    color: var(--text-main);
}

.announcement-content p {
    font-size: 0.9375rem;
}

/* Intro Grid */
.intro-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1rem;
}

.intro-grid .card {
    margin-bottom: 1rem;
}

.intro-grid ul {
    list-style: none;
}

.intro-grid li {
    position: relative;
    padding-left: 1.5rem;
    margin-bottom: 0.5rem;
    font-size: 0.875rem;
}

.intro-grid li::before {
    content: "•";
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

/* Features */
.features-section.card {
    padding: 2.5rem 1.5rem;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 1.25rem;
    margin-top: 1.5rem;
}

.features-grid .card {
    text-align: center;
    margin-bottom: 0;
    padding: 1.5rem 1rem;
    /* Nested cards should have slightly different background or simplified style */
    background: rgba(255, 255, 255, 0.4); 
    border-color: rgba(255, 255, 255, 0.2);
    box-shadow: none;
}

.dark-mode .features-grid .card {
    background: rgba(0, 0, 0, 0.2);
}

.features-grid .card:hover {
    transform: translateY(-4px);
    background: var(--card-bg); /* Highlight on hover */
    box-shadow: var(--shadow-md);
}

.feature-icon {
    width: 56px;
    height: 56px;
    background: rgb(from var(--primary-color) r g b / 0.05);
    color: var(--primary-color);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin: 0 auto 1.25rem;
}

.features-grid h4 {
    margin-bottom: 0.75rem;
    font-size: 1.125rem;
    color: var(--primary-color);
}

.features-grid p {
    font-size: 0.875rem;
    color: var(--text-muted);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 0.75rem 1.75rem;
    border-radius: 999px;
    font-weight: 600;
    text-decoration: none;
    transition: all 0.2s ease;
}

.btn-primary {
    background-color: var(--primary-color);
    color: #fff;
    box-shadow: 0 4px 12px rgb(from var(--primary-color) r g b / 0.3);
}

.btn-primary:hover {
    background-color: var(--primary-hover);
    transform: scale(1.02);
}

.btn-secondary {
    background-color: var(--card-bg);
    color: var(--primary-color);
    border: 1px solid var(--primary-color);
}

.btn-secondary:hover {
    background-color: rgb(from var(--primary-color) r g b / 0.05);
}

/* Help Sections */
.add-section {
    margin-top: 3rem;
}

.add-methods {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    justify-content: space-around;
    gap: 2rem;
}

.method {
    flex: 1;
    min-width: 250px;
    text-align: center;
}

.method-divider {
    width: 1px;
    height: 80px;
    background: #e2e8f0;
}

.qr-placeholder {
    width: 140px;
    height: 140px;
    background: #f1f5f9;
    border: 1px solid var(--card-border);
    margin: 1rem auto;
    border-radius: 12px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    overflow: hidden;
}

.qr-placeholder i {
    width: 48px;
    height: 48px;
    stroke-width: 1.5;
    margin-bottom: 0.5rem;
}

.requirement-list {
    display: grid;
    gap: 0.75rem;
    margin-top: 1rem;
}

.req-item {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 0.9375rem;
}

.req-item i {
    width: 18px;
    height: 18px;
    color: var(--accent-color);
}

/* Footer */
.footer {
    text-align: center;
    margin-top: 2rem;
    padding: 2rem 1.5rem;
    color: var(--primary-color);
    font-size: 0.95rem; /* Larger font size for both lines */
    font-weight: 500;
    opacity: 0.9;
}

.footer-links {
    margin-top: 1rem;
    display: flex;
    justify-content: center;
    gap: 1.5rem;
}

.footer-links a {
    color: var(--primary-color); /* Now using theme color in normal state */
    text-decoration: none;
    transition: opacity 0.15s ease, transform 0.15s ease;
    display: inline-flex;
    align-items: center;
}

.footer-links a:hover {
    opacity: 0.7;
    transform: translateY(-1px);
}

.link-highlight {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

.link-highlight:hover {
    text-decoration: underline;
}

/* Mobile Adjustments */
@media (max-width: 640px) {
    .container {
        padding: 1.5rem 1rem;
    }
    .hero h1 {
        font-size: 2rem;
    }
    .method-divider {
        display: none;
    }
    .intro-grid {
        grid-template-columns: 1fr;
    }
}

/* Page Specific & Reusable Components */

/* Generic Grids */
.grid-cols {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

/* QR & Card specific */
.text-center { text-align: center; }

.qr-card {
    text-align: center;
    padding: 2.5rem 1.5rem;
}

.qr-image {
    width: 200px;
    height: 200px;
    background: #f1f5f9;
    border-radius: 12px;
    margin: 1rem auto;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--card-border);
    transition: all 0.3s ease;
    overflow: hidden;
}

.dark-mode .qr-image {
    background: #1e293b;
    border-color: #334155;
}

/* Deco & Icons */
.header-deco {
    font-size: 3rem;
    margin-bottom: 1rem;
    display: block;
}

/* Navigation Links */
.back-link {
    margin-top: 2rem;
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: transform 0.2s ease;
}

.back-link:hover {
    text-decoration: underline;
    transform: translateX(-4px);
}

/* Compact Donation Teaser */
.donation-teaser {
    display: flex;
    align-items: center;
    gap: 1.25rem;
    padding: 1rem 1.5rem; /* More compact padding */
}

.donation-teaser-icon {
    width: 44px;
    height: 44px;
    background: rgba(255, 107, 107, 0.1);
    color: #ff6b6b;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.donation-teaser-body {
    flex: 1;
}

.donation-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    text-decoration: none;
    color: var(--text-main);
    transition: all 0.2s ease;
}

.donation-link:hover {
    color: var(--primary-color);
}

.donation-link:hover h3 {
    color: var(--primary-color);
}

.donation-link i {
    opacity: 0.6;
    transition: transform 0.2s ease;
}

.donation-link:hover i {
    opacity: 1;
    transform: translateX(3px);
}

.donation-teaser h3 {
    margin: 0;
    font-size: 1.1rem;
    transition: color 0.2s ease;
}

.donation-teaser p {
    margin: 2px 0 0 0;
    font-size: 0.875rem;
    color: var(--text-muted);
}

.qr-msg {
    font-size: 0.9rem;
    color: #475569; /* slate-600: 亮色模式下非常清晰 */
    opacity: 0.8;
}

.dark-mode .qr-msg {
    color: #94a3b8; /* slate-400: 暗色模式下灰白色 */
}