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

/* ==================== 赛博朋克主题（默认）==================== */
:root,
body.theme-cyber {
    --primary-color: #00ff88;
    --secondary-color: #00d4ff;
    --accent-color: #ff2e63;
    --bg-primary: #0d1117;
    --bg-secondary: #010409;
    --bg-card: rgba(0, 255, 136, 0.03);
    --bg-navbar: rgba(13, 17, 23, 0.95);
    --text-primary: #c9d1d9;
    --text-secondary: #8b949e;
    --border-color: rgba(0, 255, 136, 0.2);
    --shadow-color: rgba(0, 255, 136, 0.15);
    --neon-green: #00ff88;
    --neon-blue: #00d4ff;
    --neon-pink: #ff2e63;
    --gradient-primary: linear-gradient(135deg, #00ff88 0%, #00d4ff 100%);
    --matrix-bg: rgba(13, 17, 23, 0.05);
}

/* ==================== 深邃暗黑主题 ==================== */
body.theme-dark {
    --primary-color: #ff3333;
    --secondary-color: #ff6666;
    --accent-color: #ff9999;
    --bg-primary: #000000;
    --bg-secondary: #0a0a0a;
    --bg-card: rgba(255, 255, 255, 0.08);
    --bg-navbar: rgba(0, 0, 0, 0.95);
    --text-primary: #ffffff;
    --text-secondary: #cccccc;
    --border-color: rgba(255, 51, 51, 0.3);
    --shadow-color: rgba(255, 51, 51, 0.2);
    --neon-green: #ff3333;
    --neon-blue: #ff6666;
    --neon-pink: #ff9999;
    --gradient-primary: linear-gradient(135deg, #ff3333 0%, #ff6666 100%);
    --matrix-bg: rgba(0, 0, 0, 0.05);
}

body {
    font-family: 'Rajdhani', 'Orbitron', monospace;
    background: var(--bg-secondary);
    color: var(--text-primary);
    line-height: 1.6;
    overflow-x: hidden;
    position: relative;
    transition: background 0.3s ease, color 0.3s ease;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    position: relative;
    z-index: 10;
}

#matrixCanvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    opacity: 0.3;
}

.click-effect {
    position: fixed;
    pointer-events: none;
    z-index: 9999;
    animation: clickFade 0.8s ease-out forwards;
}

.click-ring {
    position: absolute;
    border: 2px solid var(--neon-green);
    border-radius: 50%;
    animation: ringExpand 0.8s ease-out forwards;
}

.click-particle {
    position: absolute;
    width: 4px;
    height: 4px;
    background: var(--neon-green);
    border-radius: 50%;
    box-shadow: 0 0 10px var(--neon-green);
}

@keyframes clickFade {
    0% {
        opacity: 1;
        transform: scale(0);
    }
    100% {
        opacity: 0;
        transform: scale(2);
    }
}



@keyframes ringExpand {
    0% {
        width: 0;
        height: 0;
        opacity: 1;
    }
    100% {
        width: 100px;
        height: 100px;
        opacity: 0;
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: var(--bg-navbar);
    backdrop-filter: blur(15px);
    z-index: 1000;
    padding: 0.8rem 0;
    border-bottom: 2px solid var(--border-color);
    box-shadow: 0 4px 30px var(--shadow-color);
}

.navbar .container {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 1.6rem;
    font-weight: 700;
    font-family: 'Orbitron', sans-serif;
}

.logo {
    font-size: 2.2rem;
    filter: drop-shadow(0 0 15px var(--neon-green));
}

.brand-text {
    white-space: nowrap;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: 0 0 20px var(--shadow-color);
}

.nav-links {
    display: flex;
    gap: 2rem;
    align-items: center;
    white-space: nowrap;
    margin-left: 2rem;
}

.nav-link {
    color: var(--text-primary);
    text-decoration: none;
    transition: all 0.3s;
    font-weight: 600;
    position: relative;
    padding: 0.5rem 0;
    font-size: 1.1rem;
    white-space: nowrap;
}

.nav-link::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 0;
    height: 2px;
    background: var(--neon-green);
    transition: width 0.3s;
    box-shadow: 0 0 10px var(--neon-green);
}

.nav-link:hover,
.nav-link.active {
    color: var(--neon-green);
    text-shadow: 0 0 15px var(--neon-green);
}

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

.btn-login, .btn-register {
    padding: 0.6rem 1.2rem;
    font-size: 1.1rem;
    font-weight: 600;
}

.cyber-button {
    position: relative;
    background: transparent;
    border: 2px solid var(--neon-green);
    color: var(--neon-green);
    padding: 0.75rem 1.5rem;
    border-radius: 4px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    font-size: 1rem;
    font-family: 'Orbitron', sans-serif;
    overflow: hidden;
    text-transform: uppercase;
    letter-spacing: 2px;
}

.cyber-button::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 51, 51, 0.3), transparent);
    transition: left 0.5s;
}

.cyber-button:hover::before {
    left: 100%;
}

.cyber-button:hover {
    background: rgba(255, 51, 51, 0.1);
    box-shadow: 0 0 20px var(--shadow-color), inset 0 0 20px var(--shadow-color);
    transform: translateY(-2px);
}

.cyber-button-outline {
    position: relative;
    background: transparent;
    border: 2px solid var(--neon-blue);
    color: var(--neon-blue);
    padding: 0.75rem 1.5rem;
    border-radius: 4px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    font-size: 1rem;
    font-family: 'Orbitron', sans-serif;
    overflow: hidden;
    text-transform: uppercase;
    letter-spacing: 2px;
}

.cyber-button-outline:hover {
    background: rgba(255, 102, 102, 0.1);
    box-shadow: 0 0 20px var(--shadow-color);
    transform: translateY(-2px);
}

.hero {
    min-height: 45vh;
    display: flex;
    align-items: center;
    position: relative;
    padding-top: 80px;
    padding-bottom: 30px;
    overflow: hidden;
}

.hero .container {
    width: 100%;
    position: relative;
    z-index: 10;
}

.hero-content-full {
    max-width: 1200px;
    margin: 0 auto;
    text-align: center;
    padding: 0.5rem 2rem;
}

.glitch-wrapper {
    position: relative;
    display: inline-block;
    margin-bottom: 0.3rem;
}

.hero-bg {
    position: relative;
    overflow: hidden;
}

.hero-bg-img {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, calc(-50% - 20px));
    height: 350px;
    opacity: 1;
    pointer-events: none;
    z-index: -1;
    object-fit: contain;
    user-select: none;
}

.hero-bg .hero-title {
    position: relative;
    z-index: 1;
}

.hero-title {
    font-size: 3.2rem;
    font-weight: 900;
    line-height: 1.2;
    margin-bottom: 0.3rem;
    font-family: 'Orbitron', sans-serif;
    color: var(--neon-green);
    text-shadow: 0 0 20px var(--shadow-color);
    position: relative;
}

.glitch {
    position: relative;
    animation: glitch-skew 3s infinite;
}

.glitch::before,
.glitch::after {
    content: attr(data-text);
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

.glitch::before {
    left: 2px;
    text-shadow: -2px 0 var(--neon-pink);
    clip: rect(44px, 450px, 56px, 0);
    animation: glitch-anim 5s infinite linear alternate-reverse;
}

.glitch::after {
    left: -2px;
    text-shadow: -2px 0 var(--neon-blue);
    clip: rect(44px, 450px, 56px, 0);
    animation: glitch-anim2 5s infinite linear alternate-reverse;
}

@keyframes glitch-anim {
    0% { clip: rect(12px, 9999px, 52px, 0); }
    20% { clip: rect(58px, 9999px, 12px, 0); }
    40% { clip: rect(12px, 9999px, 64px, 0); }
    60% { clip: rect(86px, 9999px, 32px, 0); }
    80% { clip: rect(28px, 9999px, 92px, 0); }
    100% { clip: rect(64px, 9999px, 16px, 0); }
}

@keyframes glitch-anim2 {
    0% { clip: rect(65px, 9999px, 99px, 0); }
    20% { clip: rect(12px, 9999px, 45px, 0); }
    40% { clip: rect(78px, 9999px, 12px, 0); }
    60% { clip: rect(34px, 9999px, 67px, 0); }
    80% { clip: rect(91px, 9999px, 23px, 0); }
    100% { clip: rect(12px, 9999px, 34px, 0); }
}

@keyframes glitch-skew {
    0% { transform: skew(0deg); }
    10% { transform: skew(-2deg); }
    20% { transform: skew(2deg); }
    30% { transform: skew(0deg); }
    100% { transform: skew(0deg); }
}

.hero-subtitle-cyber {
    font-size: 1.8rem;
    color: var(--neon-blue);
    margin-bottom: 0.6rem;
    font-family: 'Orbitron', sans-serif;
    text-shadow: 0 0 15px var(--shadow-color);
}

.hero-description-large {
    font-size: 1.1rem;
    color: var(--text-secondary);
    margin-bottom: 0;
    min-height: 35px;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
}

.typing-text {
    color: var(--text-primary);
}

.cursor {
    animation: blink 1s infinite;
    color: var(--neon-green);
    font-weight: bold;
}

@keyframes blink {
    0%, 50% { opacity: 1; }
    51%, 100% { opacity: 0; }
}

.challenges-section {
    padding: 0.5rem 0 5rem 0;
    position: relative;
}

.section-header {
    text-align: center;
    margin-bottom: 1.5rem;
}

.cyber-title {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.4rem;
    margin-top: 0.2rem;
    font-family: 'Orbitron', sans-serif;
    color: var(--neon-green);
    text-shadow: 0 0 20px var(--shadow-color);
    position: relative;
    display: inline-block;
}

.title-underline {
    width: 100px;
    height: 3px;
    background: var(--gradient-primary);
    margin: 0.4rem auto;
    box-shadow: 0 0 10px var(--neon-green);
}

.section-subtitle {
    font-size: 0.95rem;
    color: var(--text-secondary);
    margin-top: 0.3rem;
}

.activity-feed {
    margin-top: -5rem;
    margin-bottom: 0.5rem;
    padding: 0.4rem 0.8rem;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    max-width: 800px;
    margin-left: auto;
    margin-right: auto;
    min-height: 35px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.activity-item {
    display: flex;
    align-items: center;
    gap: 0.8rem;
    animation: fadeInOut 0.5s ease-in-out;
}

.activity-icon {
    font-size: 1.2rem;
    filter: drop-shadow(0 0 8px var(--neon-green));
}

.activity-text {
    color: var(--neon-blue);
    font-size: 0.9rem;
    font-weight: 500;
    text-shadow: 0 0 10px var(--shadow-color);
}

@keyframes fadeInOut {
    0% {
        opacity: 0;
        transform: translateY(-10px);
    }
    100% {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.difficulty-filter {
    display: flex;
    justify-content: center;
    gap: 0.8rem;
    margin-bottom: 1rem;
    flex-wrap: wrap;
}

.filter-btn {
    padding: 0.6rem 1.2rem;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.3s;
    font-family: 'Rajdhani', sans-serif;
    font-size: 0.95rem;
}

.filter-btn:hover,
.filter-btn.active {
    background: rgba(255, 51, 51, 0.2);
    border-color: var(--neon-green);
    color: var(--neon-green);
    box-shadow: 0 0 15px var(--shadow-color);
}

.challenges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.5rem;
}
.difficulty-description {
    min-height: 100px;
    max-width: 900px;
    margin: 0 auto 1.5rem;
    padding: 1rem 1.5rem;
    background: rgba(0, 255, 65, 0.03);
    border: 1px solid rgba(0, 255, 65, 0.15);
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.description-content {
    display: none;
    text-align: center;
    animation: fadeIn 0.3s ease;
}

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

.description-content p {
    margin: 0.4rem 0;
    color: var(--text-primary);
    font-size: 0.95rem;
    line-height: 1.6;
}

.description-content p:first-child {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: 0.6rem;
}

.novice-desc p:first-child {
    color: var(--neon-green);
}

.advanced-desc p:first-child {
    color: var(--neon-blue);
}

.advanced_aef-desc p:first-child {
    color: #ff2e4c;
}

.hard-desc p:first-child {
    color: #ffa500;
}

.expert-desc p:first-child {
    color: var(--neon-pink);
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.challenges-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 1.5rem;
}
.challenge-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    transition: all 0.3s;
    cursor: pointer;
    position: relative;
    overflow: hidden;
}

.challenge-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(255, 51, 51, 0.1), transparent);
    transition: left 0.5s;
}

.challenge-card:hover::before {
    left: 100%;
}

.challenge-card:hover {
    transform: translateY(-10px);
    border-color: var(--neon-green);
    box-shadow: 0 10px 40px var(--shadow-color);
}

.challenge-header {
    display: flex;
    justify-content: space-between;
    align-items: start;
    margin-bottom: 0.8rem;
}

.challenge-icon {
    font-size: 2.2rem;
    filter: drop-shadow(0 0 10px var(--neon-green));
}

.challenge-number {
    color: var(--neon-blue);
    font-size: 0.85rem;
    font-family: 'Orbitron', sans-serif;
}

.challenge-title {
    font-size: 1.2rem;
    font-weight: 600;
    margin-bottom: 0.6rem;
    color: var(--neon-green);
    font-family: 'Orbitron', sans-serif;
}

.challenge-description {
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 0.8rem;
    font-size: 0.9rem;
}

.challenge-meta {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding-top: 0.8rem;
    border-top: 1px solid var(--border-color);
}

.difficulty {
    padding: 0.2rem 0.6rem;
    border-radius: 4px;
    font-size: 0.8rem;
    font-weight: 600;
}

.difficulty-easy {
    background: rgba(255, 51, 51, 0.2);
    color: var(--neon-green);
    border: 1px solid var(--neon-green);
}

.difficulty-medium {
    background: rgba(255, 102, 102, 0.2);
    color: var(--neon-blue);
    border: 1px solid var(--neon-blue);
}

.difficulty-advanced_aef {
    background: rgba(255, 170, 0, 0.15);
    color: #ffaa00;
    border-color: rgba(255, 170, 0, 0.3);
}

.difficulty-hard {
    background: rgba(255, 165, 0, 0.2);
    color: #ffa500;
    border: 1px solid #ffa500;
}

.difficulty-expert {
    background: rgba(255, 153, 153, 0.2);
    color: var(--neon-pink);
    border: 1px solid var(--neon-pink);
}

.completions {
    color: var(--text-secondary);
    font-size: 0.8rem;
}

.completions.solved {
    color: var(--neon-green);
    font-weight: 600;
    text-shadow: 0 0 10px var(--shadow-color);
}

.completions.unsolved {
    color: #ff4444;
    font-weight: 600;
}

.modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.8);
    backdrop-filter: blur(5px);
}

.modal-content {
    background: var(--bg-primary);
    border: 2px solid var(--neon-green);
    border-radius: 8px;
    margin: 3% auto;
    padding: 2rem;
    width: 90%;
    max-width: 450px;
    position: relative;
    box-shadow: 0 0 40px var(--shadow-color);
    animation: modalSlideIn 0.3s ease-out;
    max-height: 90vh;
    overflow-y: auto;
}

@keyframes modalSlideIn {
    from {
        opacity: 0;
        transform: translateY(-50px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.close-btn {
    position: absolute;
    right: 1.5rem;
    top: 1.5rem;
    color: var(--text-secondary);
    font-size: 2rem;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
}

.close-btn:hover {
    color: var(--neon-green);
    text-shadow: 0 0 10px var(--neon-green);
}

.modal-title {
    color: var(--neon-green);
    font-size: 1.6rem;
    margin-bottom: 1.2rem;
    text-align: center;
    font-family: 'Orbitron', sans-serif;
    text-shadow: 0 0 15px var(--shadow-color);
}

.modal-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    color: var(--text-primary);
    font-size: 0.95rem;
    font-weight: 500;
}

.form-group input {
    padding: 0.75rem 1rem;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    color: var(--text-primary);
    font-size: 1rem;
    transition: all 0.3s;
    font-family: 'Rajdhani', sans-serif;
}

.form-group input:focus {
    outline: none;
    border-color: var(--neon-green);
    box-shadow: 0 0 15px var(--shadow-color);
}

.btn-submit {
    width: 100%;
    margin-top: 1rem;
}

.modal-footer-text {
    text-align: center;
    color: var(--text-secondary);
    margin-top: 1rem;
}

.modal-footer-text a {
    color: var(--neon-blue);
    text-decoration: none;
    transition: all 0.3s;
}

.modal-footer-text a:hover {
    color: var(--neon-green);
    text-shadow: 0 0 10px var(--neon-green);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
    padding-bottom: 0.8rem;
    border-bottom: 2px solid var(--border-color);
}

.nav-brand {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.brand-link {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    text-decoration: none;
    color: inherit;
    transition: all 0.3s;
    cursor: pointer;
}

.brand-link:hover {
    transform: scale(1.05);
    filter: drop-shadow(0 0 10px var(--shadow-color));
}

.logo {
    font-size: 2rem;
    animation: float 3s ease-in-out infinite;
}

.logo-img {
    height: 2.2rem;
    vertical-align: middle;
    filter: drop-shadow(0 0 15px var(--neon-green));
    transition: transform 0.3s ease;
}

.logo-img:hover {
    transform: scale(1.1);
}

.brand-text {
    font-family: 'Orbitron', sans-serif;
    font-size: 1.8rem;
    font-weight: 700;
    white-space: nowrap;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    text-shadow: 0 0 20px var(--shadow-color);
}

@keyframes float {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-5px);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.close-btn {
    color: var(--text-secondary);
    font-size: 2rem;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
    line-height: 1;
    padding: 0 0.5rem;
}

.close-btn:hover {
    color: var(--neon-green);
    text-shadow: 0 0 10px var(--neon-green);
    transform: scale(1.1);
}

.auth-modal {
    display: none;
    position: fixed;
    z-index: 2000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.85);
    backdrop-filter: blur(8px);
    opacity: 0;
    transition: opacity 0.3s ease;
    overflow-y: auto;
}

.auth-modal.active {
    opacity: 1;
}

.auth-container {
    max-width: 450px;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
    border: 2px solid var(--neon-green);
    box-shadow: 0 0 50px var(--shadow-color);
    padding: 1.2rem;
    margin: 2vh auto;
    max-height: 96vh;
    overflow-y: auto;
    position: relative;
}

.auth-tabs {
    display: flex;
    gap: 0.4rem;
    margin-bottom: 1rem;
    border-bottom: 2px solid var(--border-color);
    padding-bottom: 0.6rem;
}

.auth-tabs .tab-btn {
    flex: 1;
    padding: 0.6rem 0.8rem;
    background: transparent;
    border: 2px solid transparent;
    color: var(--text-secondary);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.3s;
    font-family: 'Rajdhani', sans-serif;
    font-size: 0.95rem;
    font-weight: 600;
}

.auth-tabs .tab-btn:hover {
    color: var(--neon-green);
    background: rgba(255, 51, 51, 0.1);
}

.auth-tabs .tab-btn.active {
    color: var(--neon-green);
    border-color: var(--neon-green);
    background: rgba(255, 51, 51, 0.15);
    box-shadow: 0 0 15px var(--shadow-color);
}

.auth-panel {
    display: none;
}

.auth-panel.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.auth-form {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.2rem;
}

.form-group label {
    display: block;
    color: var(--text-primary);
    margin-bottom: 0.2rem;
    font-size: 0.85rem;
    font-weight: 600;
}

.form-group input {
    width: 100%;
    padding: 0.5rem 0.7rem;
    background: var(--bg-card);
    border: 2px solid var(--border-color);
    border-radius: 4px;
    color: var(--text-primary);
    font-size: 0.9rem;
    transition: all 0.3s;
    font-family: 'Rajdhani', sans-serif;
}

.form-group input:focus {
    outline: none;
    border-color: var(--neon-green);
    box-shadow: 0 0 10px var(--shadow-color);
}

.field-hint {
    display: block;
    font-size: 0.75rem;
    margin-top: 0.15rem;
    min-height: 1em;
    color: var(--text-secondary);
    transition: all 0.3s;
    line-height: 1.2;
}

.field-hint.error {
    color: #ff4444;
}

.field-hint.success {
    color: var(--neon-green);
}

.form-group input.valid {
    border-color: var(--neon-green);
}

.form-group input.invalid {
    border-color: #ff4444;
}

.form-options {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.85rem;
    margin: 0.2rem 0;
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    color: var(--text-secondary);
    cursor: pointer;
}

.checkbox-label input[type="checkbox"] {
    width: auto;
    cursor: pointer;
}

.forgot-link {
    color: var(--neon-blue);
    text-decoration: none;
    transition: all 0.3s;
    font-size: 0.85rem;
}

.forgot-link:hover {
    color: var(--neon-green);
    text-shadow: 0 0 10px var(--neon-green);
}

.btn-submit {
    width: 100%;
    margin-top: 0.6rem;
    padding: 0.6rem 1rem;
    font-size: 0.95rem;
}

.modal-title {
    color: var(--neon-green);
    font-size: 1.4rem;
    margin-bottom: 0.8rem;
    text-align: center;
    font-family: 'Orbitron', sans-serif;
    text-shadow: 0 0 15px var(--shadow-color);
    padding-right: 2rem;
}

.close-btn {
    position: absolute;
    right: 1rem;
    top: 1rem;
    color: var(--text-secondary);
    font-size: 1.8rem;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
    line-height: 1;
    z-index: 10;
}

.close-btn:hover {
    color: var(--neon-green);
    text-shadow: 0 0 10px var(--neon-green);
}

.auth-message {
    padding: 0.6rem 0.8rem;
    border-radius: 4px;
    text-align: center;
    font-weight: 600;
    margin-bottom: 0.6rem;
    display: none;
    font-size: 0.9rem;
}

.auth-message.success {
    background: rgba(255, 51, 51, 0.15);
    border: 2px solid var(--neon-green);
    color: var(--neon-green);
}

.auth-message.error {
    background: rgba(255, 153, 153, 0.15);
    border: 2px solid var(--neon-pink);
    color: var(--neon-pink);
}

.wechat-login-container {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.qrcode-wrapper {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1.5rem;
}

.qrcode-container {
    width: 240px;
    height: 240px;
    background: rgba(255, 255, 255, 0.95);
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 15px;
    box-shadow: 0 0 30px rgba(255, 51, 51, 0.2);
    border: 2px solid rgba(255, 51, 51, 0.3);
}

.qrcode-image {
    width: 100%;
    height: 100%;
    object-fit: contain;
    border-radius: 8px;
}

.qrcode-placeholder {
    text-align: center;
    color: #333;
}

.qrcode-placeholder p {
    margin-top: 1rem;
    font-size: 0.95rem;
    color: #666;
}

.loading-spinner {
    width: 40px;
    height: 40px;
    border: 4px solid rgba(255, 51, 51, 0.2);
    border-top-color: #ff3333;
    border-radius: 50%;
    animation: spin 1s linear infinite;
    margin: 0 auto;
}

@keyframes spin {
    to { transform: rotate(360deg); }
}

.qrcode-error {
    text-align: center;
    color: #ff4444;
}

.error-icon {
    font-size: 3rem;
    margin-bottom: 1rem;
}

.retry-btn {
    margin-top: 1rem;
    padding: 0.6rem 1.5rem;
    background: #ff3333;
    color: white;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 600;
    transition: all 0.3s;
}

.retry-btn:hover {
    background: #cc0000;
    box-shadow: 0 0 20px rgba(255, 51, 51, 0.4);
    transform: translateY(-2px);
}

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

.status-text {
    font-size: 1.1rem;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
    font-weight: 600;
}

.status-text.scanned {
    color: #ff3333;
    animation: pulse 1.5s ease-in-out infinite;
}

.status-text.success {
    color: #ff3333;
    font-size: 1.3rem;
}

.status-text.expired {
    color: #ff4444;
}

@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.6; }
}

.status-subtext {
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.wechat-tips {
    background: rgba(255, 51, 51, 0.05);
    border: 1px solid rgba(255, 51, 51, 0.2);
    border-radius: 8px;
    padding: 1.2rem;
}

.tip-item {
    display: flex;
    align-items: center;
    gap: 0.8rem;
    padding: 0.6rem 0;
    color: var(--text-primary);
    font-size: 0.95rem;
}

.tip-item:not(:last-child) {
    border-bottom: 1px solid rgba(255, 51, 51, 0.1);
}

.tip-icon {
    color: #ff3333;
    font-weight: bold;
    font-size: 1.1rem;
}

.footer-simple {
    background: var(--bg-primary);
    padding: 2rem 0;
    border-top: 1px solid var(--border-color);
    text-align: center;
}

.footer-simple p {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.field-hint {
    display: block;
    font-size: 0.8rem;
    margin-top: 0.3rem;
    min-height: 1.2em;
    color: var(--text-secondary);
    transition: all 0.3s;
}

.field-hint.error {
    color: #ff4444;
}

.field-hint.success {
    color: var(--neon-green);
}

.form-group input.valid {
    border-color: var(--neon-green);
}

.form-group input.invalid {
    border-color: #ff4444;
}

.nav-links {
    display: flex;
    gap: 2rem;
    align-items: center;
    white-space: nowrap;
    margin-left: 2rem;
}

#userSection {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.user-name {
    color: var(--neon-green);
    font-weight: 600;
    font-size: 1rem;
    text-shadow: 0 0 10px var(--shadow-color);
    font-family: 'Orbitron', sans-serif;
}

.btn-logout {
    padding: 0.5rem 1rem;
    font-size: 0.9rem;
}

.welcome-banner {
    position: fixed;
    top: 70px;
    left: 0;
    width: 100%;
    background: linear-gradient(135deg, rgba(255, 51, 51, 0.15) 0%, rgba(255, 102, 102, 0.15) 100%);
    border-bottom: 2px solid var(--neon-green);
    box-shadow: 0 4px 20px var(--shadow-color);
    z-index: 999;
    transform: translateY(-100%);
    opacity: 0;
    transition: all 0.5s ease;
    overflow: hidden;
}

.welcome-banner.show {
    transform: translateY(0);
    opacity: 1;
}

.banner-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    position: relative;
}

.progress-bar {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 3px;
    background: rgba(255, 51, 51, 0.2);
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    width: 100%;
    transform-origin: left;
    animation: progressShrink 3s linear forwards;
    box-shadow: 0 0 10px var(--neon-green);
}

@keyframes progressShrink {
    from {
        transform: scaleX(1);
    }
    to {
        transform: scaleX(0);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.welcome-text {
    color: var(--neon-green);
    font-size: 1.2rem;
    font-weight: 600;
    text-align: center;
    margin: 0;
    font-family: 'Orbitron', sans-serif;
    text-shadow: 0 0 20px var(--shadow-color);
    animation: textFlicker 0.1s infinite;
}

@keyframes textFlicker {
    0%, 100% {
        opacity: 1;
        text-shadow: 0 0 20px var(--shadow-color), 0 0 30px var(--shadow-color);
    }
    50% {
        opacity: 0.8;
        text-shadow: 0 0 10px var(--shadow-color), 0 0 20px var(--shadow-color);
    }
}

/* ==================== ICP 备案号 ==================== */
.footer-icp {
    text-align: center;
    padding: 16px 10px 20px;
    font-size: 12px;
    color: var(--text-muted, rgba(255,255,255,0.3));
    letter-spacing: 0.5px;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.05));
}

.leaderboard-float {
    position: fixed;
    right: 10px;
    top: 100px;
    width: 320px;
    background: var(--bg-primary);
    border: 2px solid var(--neon-green);
    border-radius: 8px;
    box-shadow: 0 0 30px var(--shadow-color);
    z-index: 999;
    transition: all 0.3s ease;
    backdrop-filter: blur(10px);
}

.leaderboard-float.minimized {
    overflow: hidden;
}

.leaderboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 14px;
    background: linear-gradient(135deg, rgba(0, 255, 136, 0.08) 0%, rgba(0, 212, 255, 0.08) 100%);
    border-bottom: 1px solid var(--border-color);
    cursor: pointer;
    min-height: 44px;
}

.leaderboard-header h3 {
    margin: 0;
    color: var(--neon-green);
    font-size: 0.95rem;
    font-family: 'Orbitron', sans-serif;
    text-shadow: 0 0 10px var(--shadow-color);
    white-space: nowrap;
    overflow: hidden;
    transition: opacity 0.3s ease;
}

.leaderboard-float.minimized .leaderboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 14px;
    cursor: pointer;
    border-bottom: none;
}

.leaderboard-float.minimized .leaderboard-toggle {
    font-size: 1.5rem;
    border: 2px solid var(--neon-green);
    width: 34px;
    height: 34px;
}

/* ===== 排行榜选项卡 ===== */
.leaderboard-tabs {
    display: flex;
    border-bottom: 1px solid var(--border-color);
    background: rgba(0, 0, 0, 0.15);
}

.lb-tab {
    flex: 1;
    padding: 8px 4px;
    background: transparent;
    color: var(--text-secondary);
    border: none;
    border-bottom: 2px solid transparent;
    cursor: pointer;
    font-family: 'Orbitron', sans-serif;
    font-size: 0.8rem;
    font-weight: 500;
    transition: all 0.2s;
    letter-spacing: 1px;
}

.lb-tab:hover {
    color: var(--neon-green);
    background: rgba(0, 255, 136, 0.05);
}

.lb-tab.active {
    color: var(--neon-green);
    border-bottom-color: var(--neon-green);
    text-shadow: 0 0 8px var(--shadow-color);
}

/* ===== 排行榜分值说明条 ===== */
.leaderboard-score-bar {
    display: flex;
    justify-content: space-around;
    padding: 6px 8px;
    border-bottom: 1px solid var(--border-color);
    background: rgba(0, 0, 0, 0.1);
}

.score-tag {
    font-size: 0.75rem;
    font-weight: 600;
    font-family: 'Rajdhani', sans-serif;
    padding: 2px 6px;
    border-radius: 3px;
    white-space: nowrap;
}

.score-tag.novice {
    color: var(--neon-green);
    background: rgba(0, 255, 136, 0.1);
    border: 1px solid rgba(0, 255, 136, 0.25);
}

.score-tag.advanced {
    color: var(--neon-blue);
    background: rgba(0, 212, 255, 0.1);
    border: 1px solid rgba(0, 212, 255, 0.25);
}

.score-tag.hard {
    color: #ffa500;
    background: rgba(255, 165, 0, 0.1);
    border: 1px solid rgba(255, 165, 0, 0.25);
}

.score-tag.expert {
    color: var(--neon-pink);
    background: rgba(255, 46, 99, 0.1);
    border: 1px solid rgba(255, 46, 99, 0.25);
}

.leaderboard-toggle {
    background: transparent;
    border: 1px solid var(--neon-green);
    color: var(--neon-green);
    width: 24px;
    height: 24px;
    border-radius: 4px;
    cursor: pointer;
    font-size: 1.2rem;
    line-height: 1;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s;
    padding: 0;
    flex-shrink: 0;
}

.leaderboard-toggle:hover {
    background: rgba(0, 255, 136, 0.15);
    box-shadow: 0 0 10px var(--shadow-color);
}

.leaderboard-content {
    max-height: 380px;
    overflow-y: auto;
    padding: 8px;
}

.leaderboard-float.minimized .leaderboard-content {
    display: none;
}

.leaderboard-float.minimized .leaderboard-tabs,
.leaderboard-float.minimized .leaderboard-score-bar {
    display: none;
}

.leaderboard-list {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.leaderboard-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 10px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 6px;
    transition: all 0.2s;
}

.leaderboard-item:hover {
    background: rgba(0, 255, 136, 0.06);
    border-color: var(--neon-green);
    transform: translateX(-3px);
}

.leaderboard-item.current-user {
    border-color: var(--neon-blue);
    background: rgba(0, 212, 255, 0.08);
    box-shadow: 0 0 12px var(--shadow-color);
}

.rank-badge {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 800;
    font-size: 1.25rem;
    font-family: 'Orbitron', sans-serif;
    flex-shrink: 0;
}

.rank-1 {
    background: linear-gradient(135deg, #FFD700, #FFA500);
    color: #000;
    box-shadow: 0 0 12px rgba(255, 215, 0, 0.6);
}

.rank-2 {
    background: linear-gradient(135deg, #C0C0C0, #A0A0A0);
    color: #000;
    box-shadow: 0 0 12px rgba(192, 192, 192, 0.6);
}

.rank-3 {
    background: linear-gradient(135deg, #CD7F32, #B87333);
    color: #fff;
    box-shadow: 0 0 12px rgba(205, 127, 50, 0.6);
}

.rank-other {
    background: rgba(0, 255, 136, 0.12);
    color: var(--neon-green);
    border: 1px solid var(--neon-green);
}

.user-info {
    flex: 1;
    min-width: 0;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 8px;
}

.username {
    color: var(--text-primary);
    font-size: 1.05rem;
    font-weight: 700;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    flex: 1;
    min-width: 0;
}

.solved-count {
    color: var(--neon-blue);
    font-size: 0.82rem;
    font-weight: 700;
    flex-shrink: 0;
}

.loading-item {
    text-align: center;
    color: var(--text-secondary);
    padding: 20px;
    font-size: 0.9rem;
}

.leaderboard-content::-webkit-scrollbar {
    width: 5px;
}

.leaderboard-content::-webkit-scrollbar-track {
    background: var(--bg-card);
    border-radius: 3px;
}

.leaderboard-content::-webkit-scrollbar-thumb {
    background: var(--neon-green);
    border-radius: 3px;
}

.leaderboard-content::-webkit-scrollbar-thumb:hover {
    background: var(--neon-blue);
}

/* ===== 分页 ===== */
.pagination {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    margin-top: 2rem;
    padding: 1rem 0;
}

.page-btn {
    padding: 0.5rem 1rem;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    border-radius: 4px;
    cursor: pointer;
    transition: all 0.3s;
    font-family: 'Rajdhani', sans-serif;
    font-size: 0.95rem;
    min-width: 40px;
}

.page-btn:hover:not(:disabled) {
    background: rgba(0, 255, 136, 0.1);
    border-color: var(--neon-green);
    color: var(--neon-green);
    box-shadow: 0 0 15px var(--shadow-color);
}

.page-btn.active {
    background: rgba(0, 255, 136, 0.15);
    border-color: var(--neon-green);
    color: var(--neon-green);
    box-shadow: 0 0 15px var(--shadow-color);
}

.page-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.page-info {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin: 0 1rem;
}

.page-ellipsis {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin: 0 0.5rem;
}

/* ==================== 个人中心样式 ==================== */
.profile-modal .modal-content {
    max-width: 520px;
}
.profile-container {
    max-width: 520px !important;
}
.profile-section {
    margin-bottom: 20px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border-color);
}
.profile-section:last-child {
    border-bottom: none;
    margin-bottom: 0;
    padding-bottom: 0;
}
.profile-avatar {
    text-align: center;
    font-size: 3rem;
    margin-bottom: 12px;
    filter: drop-shadow(0 0 20px var(--neon-green));
}
.profile-details {
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.profile-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 6px 12px;
    background: var(--bg-card);
    border-radius: 4px;
    border: 1px solid var(--border-color);
}
.profile-label {
    color: var(--text-secondary);
    font-size: 0.85rem;
    font-weight: 500;
}
.profile-value {
    color: var(--neon-blue);
    font-size: 0.9rem;
    font-weight: 600;
    font-family: 'Orbitron', sans-serif;
}
.profile-section-title {
    color: var(--neon-green);
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 8px;
    font-family: 'Orbitron', sans-serif;
    text-shadow: 0 0 10px var(--shadow-color);
}
.profile-hint {
    color: var(--text-secondary);
    font-size: 0.8rem;
    margin-bottom: 8px;
}
.profile-form-row {
    display: flex;
    gap: 8px;
    align-items: center;
}
.profile-input {
    flex: 1;
    padding: 8px 12px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: 4px;
    color: var(--text-primary);
    font-size: 0.9rem;
    font-family: 'Rajdhani', sans-serif;
    transition: all 0.3s;
}
.profile-input:focus {
    outline: none;
    border-color: var(--neon-green);
    box-shadow: 0 0 10px var(--shadow-color);
}
.profile-form-group {
    margin-bottom: 6px;
}
.profile-btn {
    padding: 8px 16px !important;
    font-size: 0.85rem !important;
    white-space: nowrap;
}
.profile-info {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.theme-toggle-btn {
    background: transparent;
    border: none;
    font-size: 1.8rem;
    cursor: pointer;
    padding: 0.2rem;
    line-height: 1;
    transition: transform 0.3s ease;
}
.theme-toggle-btn:hover {
    transform: scale(1.2);
}

/* ===== 通关特效 ===== */
#victoryOverlay {
    position: fixed; top: 0; left: 0; width: 100%; height: 100%;
    z-index: 99999;
    display: flex; align-items: center; justify-content: center;
    pointer-events: none;
}

.victory-glow {
    position: absolute;
    width: 600px; height: 600px;
    background: radial-gradient(circle, rgba(255,51,51,0.3) 0%, rgba(255,102,102,0.15) 40%, transparent 70%);
    border-radius: 50%;
    animation: victoryPulse 2s ease-in-out infinite;
    pointer-events: none;
}

.victory-text {
    position: relative;
    color: #ff3333;
    font-family: 'Orbitron', sans-serif;
    font-size: 3.2rem;
    font-weight: 900;
    text-align: center;
    text-shadow: 0 0 30px rgba(255,51,51,0.8), 0 0 60px rgba(255,51,51,0.4), 0 0 100px rgba(255,102,102,0.3);
    animation: victoryTextIn 1s ease-out, victoryFloat 3s ease-in-out infinite 1s;
    line-height: 1.5;
    padding: 40px;
    max-width: 800px;
    letter-spacing: 3px;
}

@keyframes victoryPulse {
    0%, 100% { transform: scale(1); opacity: 0.6; }
    50% { transform: scale(1.3); opacity: 1; }
}

@keyframes victoryTextIn {
    0% { transform: scale(0.3); opacity: 0; }
    100% { transform: scale(1); opacity: 1; }
}

@keyframes victoryFloat {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-15px); }
}

/* ==================== 新手村45题专属通关特效 ==================== */

@keyframes novicePulse {
    0%, 100% { transform: scale(1); opacity: 0.5; }
    50% { transform: scale(1.4); opacity: 1; }
}

@keyframes noviceTextIn {
    0% { transform: scale(0.2); opacity: 0; }
    50% { transform: scale(1.15); opacity: 1; }
    100% { transform: scale(1); opacity: 1; }
}

@keyframes noviceFloat {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-18px); }
}

/* ==================== 底部悬浮信息栏 ==================== */
.footer-simple {
    position: fixed;
    bottom: 0;
    left: 0;
    width: 100%;
    z-index: 9999;
    background: var(--bg-primary, #0a0a1a);
    border-top: 1px solid var(--border-color, rgba(255,255,255,0.06));
    padding: 10px 0;
    text-align: center;
    backdrop-filter: blur(6px);
}

.footer-simple .container p {
    margin: 0;
    font-size: 0.85rem;
    color: #ffffff;
    font-family: 'Rajdhani', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    letter-spacing: 0.5px;
}

/* 页面底部留出 footter 高度，防止内容被遮挡 */
body {
    padding-bottom: 50px;
}