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

:root {
    --primary-color: #667eea;
    --secondary-color: #f5576c;
    --success-color: #4facfe;
    --bg-color: #f5f7fa;
    --card-shadow: 0 10px 40px rgba(0, 0, 0, 0.1);
    --card-hover-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
}

body {
    background: var(--bg-color);
    font-family: 'Segoe UI', 'PingFang SC', 'Microsoft YaHei', sans-serif;
    min-height: 100vh;
    overflow-x: hidden;
}

.navbar {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    box-shadow: 0 4px 30px rgba(0, 0, 0, 0.08);
    border-bottom: 1px solid rgba(255, 255, 255, 0.3);
    padding: 0.75rem 0;
}

.navbar-brand {
    color: var(--primary-color);
    font-weight: 800;
    font-size: 1.5rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.sidebar {
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    box-shadow: 4px 0 30px rgba(0, 0, 0, 0.05);
    min-height: calc(100vh - 72px);
    padding-top: 1.5rem;
    position: fixed;
    top: 72px;
    bottom: 0;
    left: 0;
    width: 260px;
    z-index: 100;
    overflow-y: auto;
    border-right: 1px solid rgba(255, 255, 255, 0.5);
}

.sidebar .nav-link {
    color: #5a6c7d;
    padding: 14px 24px;
    border-radius: 12px;
    margin: 6px 16px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    align-items: center;
    gap: 12px;
    font-weight: 500;
    position: relative;
    overflow: hidden;
}

.sidebar .nav-link::before {
    content: '';
    position: absolute;
    left: 0;
    top: 0;
    height: 100%;
    width: 0;
    background: var(--primary-color);
    transition: width 0.3s ease;
    z-index: -1;
}

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

.sidebar .nav-link:hover,
.sidebar .nav-link.active {
    color: white;
    transform: translateX(4px);
}

.main-content {
    padding: 2rem;
    margin-left: 260px;
    margin-top: 72px;
    animation: fadeInUp 0.6s ease-out;
}

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

.card {
    border: none;
    border-radius: 20px;
    box-shadow: var(--card-shadow);
    margin-bottom: 1.5rem;
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    background: rgba(255, 255, 255, 0.9);
    backdrop-filter: blur(10px);
    overflow: hidden;
}

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

.card-header {
    background: var(--primary-color);
    color: white;
    border-radius: 20px 20px 0 0 !important;
    font-weight: 700;
    padding: 1.25rem 1.5rem;
    border: none;
    display: flex;
    align-items: center;
    gap: 0.75rem;
}

.btn-primary {
    background: var(--primary-color);
    border: none;
    border-radius: 12px;
    padding: 0.75rem 2rem;
    font-weight: 600;
    transition: all 0.3s ease;
    box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.5);
}

.btn-sm {
    border-radius: 10px;
    padding: 0.5rem 1rem;
}

.overlay {
    display: none;
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0, 0, 0, 0.5);
    backdrop-filter: blur(4px);
    z-index: 99;
    animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

.overlay.active {
    display: block;
}

@media (max-width: 992px) {
    .sidebar {
        position: fixed;
        top: 72px;
        left: -280px;
        transition: left 0.4s cubic-bezier(0.4, 0, 0.2, 1);
        width: 280px;
        z-index: 101;
    }

    .sidebar.active {
        left: 0;
    }

    .main-content {
        margin-left: 0;
        padding: 1.25rem;
    }
}

.modal-content {
    border-radius: 20px;
    border: none;
    overflow: hidden;
}

.modal-header {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 1.25rem 1.5rem;
}

.form-control, .form-select {
    border-radius: 12px;
    padding: 0.75rem 1rem;
    border: 2px solid #e2e8f0;
    transition: all 0.3s ease;
}

.form-control:focus, .form-select:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 0.25rem rgba(102, 126, 234, 0.15);
}

.alert {
    border-radius: 16px;
    border: none;
    padding: 1.25rem;
}

.alert-success {
    background: rgba(72, 187, 120, 0.1);
    color: #22543d;
}

.alert-info {
    background: rgba(79, 172, 254, 0.1);
    color: #2c5282;
}

.alert-danger {
    background: rgba(245, 87, 108, 0.1);
    color: #742a2a;
}

.empty-state {
    text-align: center;
    padding: 4rem 2rem;
}

.empty-state i {
    font-size: 4rem;
    color: #cbd5e0;
    margin-bottom: 1rem;
}

.empty-state h5 {
    color: #718096;
    font-weight: 600;
}

.page-title {
    font-weight: 800;
    color: var(--primary-color);
}

.auth-card {
    max-width: 450px;
    margin: 2rem auto;
}

.auth-card .card-header {
    text-align: center;
    font-size: 1.25rem;
}

.auth-card .card-body {
    padding: 2rem;
}

.table {
    margin-bottom: 0;
}

.table thead th {
    border-top: none;
    font-weight: 700;
    color: #2d3748;
}

.stat-card {
    text-align: center;
    padding: 1.5rem;
    background: white;
    border-radius: 16px;
    box-shadow: var(--card-shadow);
    transition: all 0.3s ease;
}

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

.stat-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 800;
    color: var(--primary-color);
}

.stat-label {
    color: #718096;
    font-weight: 500;
    margin-top: 0.5rem;
}

.file-item {
    border: 1px solid #e2e8f0;
    border-radius: 16px;
    padding: 1.25rem;
    margin-bottom: 1rem;
    transition: all 0.3s ease;
    background: white;
}

.file-item:hover {
    box-shadow: 0 4px 20px rgba(0, 0, 0, 0.08);
    transform: translateY(-3px);
}

.file-icon {
    font-size: 2rem;
    color: var(--primary-color);
    margin-right: 1rem;
}

.file-name {
    font-weight: 700;
    font-size: 1.1rem;
    color: #2d3748;
}

.file-meta {
    font-size: 0.9rem;
    color: #718096;
}

.user-avatar {
    width: 100px;
    height: 100px;
    border-radius: 50%;
    background: var(--primary-color);
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    font-size: 2.5rem;
    margin: 0 auto 20px;
}

.nav-tabs {
    border: none;
    margin-bottom: 1.5rem;
}

.nav-tabs .nav-link {
    color: #5a6c7d;
    font-weight: 600;
    padding: 0.75rem 1.5rem;
    border: none;
    border-radius: 12px;
    margin-right: 0.5rem;
    transition: all 0.3s ease;
}

.nav-tabs .nav-link:hover {
    background: rgba(102, 126, 234, 0.1);
    color: #667eea;
}

.nav-tabs .nav-link.active {
    background: var(--primary-color);
    color: white;
}

.link-item {
    background: rgba(255, 255, 255, 0.5);
    padding: 1rem;
    border-radius: 12px;
    transition: all 0.3s ease;
}

.link-item:hover {
    background: rgba(255, 255, 255, 0.8);
}

.form-label {
    font-weight: 600;
    color: #2d3748;
    margin-bottom: 0.5rem;
}

.upload-area {
    border: 3px dashed #cbd5e0;
    border-radius: 20px;
    padding: 4rem 2rem;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background: rgba(255, 255, 255, 0.5);
}

.upload-area:hover {
    border-color: var(--primary-color);
    background: rgba(102, 126, 234, 0.05);
    transform: scale(1.02);
}

.upload-area.dragover {
    border-color: var(--primary-color);
    background: rgba(102, 126, 234, 0.1);
}

.upload-area i {
    font-size: 4rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.progress {
    height: 8px;
    border-radius: 4px;
    background: #e2e8f0;
}

.progress-bar {
    background: var(--primary-color);
    border-radius: 4px;
}

.file-preview {
    max-height: 400px;
    overflow-y: auto;
    margin-top: 1.5rem;
}

.preview-item {
    display: flex;
    align-items: center;
    padding: 1rem;
    border: 1px solid #e2e8f0;
    border-radius: 12px;
    margin-bottom: 0.75rem;
    background: white;
    transition: all 0.3s ease;
}

.preview-item:hover {
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.preview-thumb {
    width: 60px;
    height: 60px;
    object-fit: cover;
    margin-right: 1rem;
    border-radius: 10px;
    background: #f7fafc;
    display: flex;
    align-items: center;
    justify-content: center;
}

.preview-thumb i {
    font-size: 1.5rem;
    color: #a0aec0;
}

.feature-card {
    text-align: center;
    padding: 2rem 1rem;
    border-radius: 16px;
    transition: all 0.3s ease;
    background: rgba(255, 255, 255, 0.5);
    backdrop-filter: blur(5px);
}

.feature-card:hover {
    background: white;
    transform: translateY(-5px);
}

.feature-icon {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 1rem;
    display: inline-block;
}

.feature-card h5 {
    font-weight: 700;
    color: #2d3748;
    margin-bottom: 0.5rem;
}

.feature-card p {
    color: #718096;
    font-size: 0.9rem;
}

.welcome-section {
    text-align: center;
    padding: 3rem 2rem;
    background: white;
    border-radius: 24px;
    margin-bottom: 2rem;
    box-shadow: var(--card-shadow);
    position: relative;
    overflow: hidden;
}

.welcome-section::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 4px;
    background: var(--primary-color);
}

.welcome-section h1 {
    color: var(--primary-color);
    font-weight: 800;
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.welcome-section p {
    color: #718096;
    font-size: 1.1rem;
    max-width: 600px;
    margin: 0 auto;
}

.announcement-banner {
    background: var(--secondary-color);
    border-radius: 20px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    color: white;
    box-shadow: 0 8px 30px rgba(245, 87, 108, 0.3);
    position: relative;
    overflow: hidden;
}

.footer {
    background: #1a202c;
    color: white;
    padding: 2.5rem 0;
    margin-top: 3rem;
    border-radius: 30px 30px 0 0;
}

.footer p {
    margin: 0.5rem 0;
    opacity: 0.8;
}