:root {
    --primary: #0d6efd;
    --primary-dark: #0b5ed7;
    --primary-light: #e7f1ff;
    --dark: #0f172a;
    --gray-900: #0f172a;
    --gray-800: #1e293b;
    --gray-700: #334155;
    --gray-600: #475569;
    --gray-500: #64748b;
    --gray-400: #94a3b8;
    --gray-300: #cbd5e1;
    --gray-200: #e2e8f0;
    --gray-100: #f1f5f9;
    --gray-50: #f8fafc;
    --white: #ffffff;
    --success: #10b981;
    --success-light: #ecfdf5;
    --warning: #f59e0b;
    --warning-light: #fffbeb;
    --danger: #ef4444;
    --danger-light: #fef2f2;
    --radius: 12px;
    --radius-sm: 8px;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.08), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    color: var(--gray-800);
    background-color: #f8fafc;
    line-height: 1.6;
    font-size: 15px;
}

a {
    color: var(--primary);
    text-decoration: none;
    transition: color 0.15s ease;
}

a:hover {
    color: var(--primary-dark);
}

.container {
    max-width: 1140px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.help-header {
    background: var(--white);
    border-bottom: 1px solid var(--gray-200);
    position: sticky;
    top: 0;
    z-index: 100;
    padding: 14px 0;
}

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

.brand-group {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-main {
    font-size: 19px;
    font-weight: 800;
    color: var(--dark);
    display: flex;
    align-items: center;
    gap: 8px;
}

.logo-main img {
    border-radius: 6px;
}

.logo-main .badge-help {
    font-size: 11px;
    font-weight: 700;
    text-transform: uppercase;
    background: var(--primary-light);
    color: var(--primary);
    padding: 3px 8px;
    border-radius: 6px;
    letter-spacing: 0.5px;
}

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

.nav-link-item {
    font-size: 14px;
    font-weight: 500;
    color: var(--gray-600);
}

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

.btn-app {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    background: var(--primary);
    color: var(--white);
    padding: 7px 16px;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    transition: all 0.15s ease;
}

.btn-app:hover {
    background: var(--primary-dark);
    color: var(--white);
    transform: translateY(-1px);
}

/* Hero Search */
.hero-help {
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    color: var(--white);
    padding: 50px 0 60px;
    text-align: center;
    position: relative;
    overflow: hidden;
}

.hero-help::after {
    content: '';
    position: absolute;
    top: -50%;
    left: 50%;
    transform: translateX(-50%);
    width: 600px;
    height: 300px;
    background: radial-gradient(circle, rgba(13, 110, 253, 0.25) 0%, rgba(13, 110, 253, 0) 70%);
    pointer-events: none;
}

.hero-help h1 {
    font-size: 32px;
    font-weight: 800;
    margin-bottom: 12px;
    letter-spacing: -0.5px;
}

.hero-help p {
    font-size: 16px;
    color: var(--gray-300);
    max-width: 600px;
    margin: 0 auto 30px;
}

.search-box-wrapper {
    max-width: 620px;
    margin: 0 auto;
    position: relative;
}

.search-input {
    width: 100%;
    padding: 16px 20px 16px 50px;
    font-size: 15px;
    border-radius: var(--radius);
    border: 2px solid transparent;
    background: var(--white);
    color: var(--gray-800);
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.2);
    outline: none;
    transition: all 0.2s ease;
}

.search-input:focus {
    border-color: var(--primary);
    box-shadow: 0 10px 25px rgba(13, 110, 253, 0.3);
}

.search-icon-pos {
    position: absolute;
    left: 18px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--gray-400);
    font-size: 18px;
}

/* Category Grid */
.section-title {
    font-size: 22px;
    font-weight: 800;
    color: var(--dark);
    margin-bottom: 8px;
    letter-spacing: -0.3px;
}

.section-subtitle {
    font-size: 14px;
    color: var(--gray-500);
    margin-bottom: 28px;
}

.category-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
    gap: 20px;
    margin-bottom: 48px;
}

.category-card {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius);
    padding: 24px;
    transition: all 0.2s ease;
    display: flex;
    flex-direction: column;
    height: 100%;
}

.category-card:hover {
    border-color: var(--primary);
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
}

.cat-header {
    display: flex;
    align-items: center;
    gap: 14px;
    margin-bottom: 12px;
}

.cat-icon {
    font-size: 28px;
    width: 48px;
    height: 48px;
    display: flex;
    align-items: center;
    justify-content: center;
    background: var(--gray-100);
    border-radius: 10px;
}

.cat-title {
    font-size: 17px;
    font-weight: 700;
    color: var(--dark);
    margin: 0;
}

.cat-desc {
    font-size: 13.5px;
    color: var(--gray-600);
    line-height: 1.5;
    flex-grow: 1;
    margin-bottom: 16px;
}

.cat-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 12.5px;
    font-weight: 600;
    color: var(--primary);
    border-top: 1px solid var(--gray-100);
    padding-top: 14px;
}

/* Articles List / Cards */
.article-item-card {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius-sm);
    padding: 18px 20px;
    margin-bottom: 12px;
    display: flex;
    align-items: flex-start;
    gap: 14px;
    transition: all 0.15s ease;
}

.article-item-card:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow);
    transform: translateX(4px);
}

.art-icon {
    font-size: 20px;
    margin-top: 2px;
}

.art-info h4 {
    font-size: 15.5px;
    font-weight: 700;
    color: var(--dark);
    margin-bottom: 4px;
}

.art-info p {
    font-size: 13.5px;
    color: var(--gray-500);
    margin-bottom: 6px;
}

.art-meta {
    font-size: 12px;
    color: var(--gray-400);
    display: flex;
    gap: 12px;
}

/* Breadcrumbs */
.breadcrumb-nav {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 13px;
    color: var(--gray-500);
    margin-bottom: 24px;
    flex-wrap: wrap;
}

.breadcrumb-nav a {
    color: var(--gray-600);
    font-weight: 500;
}

.breadcrumb-nav a:hover {
    color: var(--primary);
}

.breadcrumb-sep {
    color: var(--gray-300);
}

/* Article View Layout */
.article-layout {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 280px;
    gap: 36px;
    margin-top: 20px;
    margin-bottom: 60px;
}

.article-main-content {
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius);
    padding: 36px 40px;
}

.article-header {
    border-bottom: 1px solid var(--gray-200);
    padding-bottom: 24px;
    margin-bottom: 30px;
}

.article-header h1 {
    font-size: 26px;
    font-weight: 800;
    color: var(--dark);
    line-height: 1.35;
    margin-bottom: 14px;
}

.article-meta-bar {
    display: flex;
    align-items: center;
    gap: 16px;
    font-size: 13px;
    color: var(--gray-500);
    flex-wrap: wrap;
}

.badge-category {
    background: var(--primary-light);
    color: var(--primary);
    font-weight: 700;
    padding: 4px 10px;
    border-radius: 6px;
    font-size: 12px;
}

/* Article Body Typography */
.article-body {
    font-size: 15px;
    color: var(--gray-700);
    line-height: 1.8;
}

.article-body h2 {
    font-size: 20px;
    font-weight: 800;
    color: var(--dark);
    margin-top: 36px;
    margin-bottom: 14px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--gray-100);
}

.article-body h3 {
    font-size: 16.5px;
    font-weight: 700;
    color: var(--dark);
    margin-top: 24px;
    margin-bottom: 10px;
}

.article-body p {
    margin-bottom: 18px;
}

.article-body ul, .article-body ol {
    margin-left: 24px;
    margin-bottom: 20px;
}

.article-body li {
    margin-bottom: 8px;
}

.article-body code {
    background: var(--gray-100);
    color: #b91c1c;
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 13.5px;
    font-family: Consolas, Monaco, monospace;
}

.article-body .alert {
    padding: 16px 20px;
    border-radius: var(--radius-sm);
    margin: 24px 0;
    font-size: 14px;
    line-height: 1.6;
}

.article-body .alert-info {
    background: #eff6ff;
    border-left: 4px solid var(--primary);
    color: #1e40af;
}

.article-body .alert-success {
    background: var(--success-light);
    border-left: 4px solid var(--success);
    color: #065f46;
}

.article-body .alert-warning {
    background: var(--warning-light);
    border-left: 4px solid var(--warning);
    color: #92400e;
}

/* Sidebar TOC */
.sidebar-toc {
    position: sticky;
    top: 90px;
    background: var(--white);
    border: 1px solid var(--gray-200);
    border-radius: var(--radius);
    padding: 20px;
    font-size: 13.5px;
}

.toc-title {
    font-size: 14px;
    font-weight: 700;
    text-transform: uppercase;
    color: var(--gray-400);
    letter-spacing: 0.5px;
    margin-bottom: 12px;
}

.toc-list {
    list-style: none;
}

.toc-list li {
    margin-bottom: 8px;
}

.toc-list a {
    color: var(--gray-600);
    display: block;
    line-height: 1.4;
}

.toc-list a:hover {
    color: var(--primary);
}

/* Feedback Box */
.feedback-box {
    margin-top: 40px;
    padding-top: 24px;
    border-top: 1px solid var(--gray-200);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: gap;
}

.feedback-buttons {
    display: flex;
    gap: 8px;
}

.btn-feedback {
    border: 1px solid var(--gray-300);
    background: var(--white);
    padding: 6px 14px;
    border-radius: 6px;
    font-size: 13px;
    cursor: pointer;
    transition: all 0.15s ease;
}

.btn-feedback:hover {
    background: var(--gray-50);
    border-color: var(--gray-400);
}

/* Footer */
.help-footer {
    background: var(--dark);
    color: var(--gray-400);
    padding: 40px 0 30px;
    font-size: 13.5px;
    margin-top: 60px;
}

.help-footer .footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
    border-bottom: 1px solid var(--gray-800);
    padding-bottom: 24px;
    margin-bottom: 24px;
    flex-wrap: wrap;
    gap: 20px;
}

.help-footer .footer-links {
    display: flex;
    gap: 20px;
}

.help-footer a {
    color: var(--gray-400);
}

.help-footer a:hover {
    color: var(--white);
}

@media (max-width: 900px) {
    .article-layout {
        grid-template-columns: 1fr;
    }
    .sidebar-toc {
        display: none;
    }
    .category-grid {
        grid-template-columns: 1fr;
    }
    .article-main-content {
        padding: 24px;
    }
}