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

:root {
    --blue: #007AFF;
    --blue-dark: #0056CC;
    --bg: #F5F5F7;
    --surface: #FFFFFF;
    --text: #1D1D1F;
    --text-secondary: #6E6E73;
    --border: #D2D2D7;
    --radius: 12px;
    --shadow: 0 2px 12px rgba(0,0,0,0.08);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.12);
    --max-width: 1100px;
}

html {
    scroll-behavior: smooth;
    font-size: 16px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0 24px;
}

a {
    color: var(--blue);
    text-decoration: none;
}
a:hover {
    text-decoration: underline;
}

h2 {
    font-size: 2rem;
    font-weight: 700;
    text-align: center;
    margin-bottom: 12px;
}
.section-desc {
    text-align: center;
    color: var(--text-secondary);
    margin-bottom: 48px;
    font-size: 1.05rem;
}

/* ========== Navbar ========== */
.navbar {
    background: rgba(255,255,255,0.9);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 100;
}
.navbar .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 56px;
}
.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-weight: 700;
    font-size: 1.15rem;
    color: var(--text);
}
.logo:hover {
    text-decoration: none;
}
.nav-links {
    display: flex;
    list-style: none;
    gap: 32px;
}
.nav-links a {
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    transition: color 0.2s;
}
.nav-links a:hover {
    color: var(--blue);
    text-decoration: none;
}
.hamburger {
    display: none;
    flex-direction: column;
    gap: 5px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 4px;
}
.hamburger span {
    display: block;
    width: 22px;
    height: 2px;
    background: var(--text);
    border-radius: 1px;
    transition: 0.3s;
}

/* ========== Hero ========== */
.hero {
    background: linear-gradient(135deg, #000 0%, #1a1a2e 50%, #16213e 100%);
    color: #fff;
    text-align: center;
    padding: 80px 24px 72px;
}
.hero h1 {
    font-size: 2.8rem;
    font-weight: 800;
    letter-spacing: -0.5px;
    margin-bottom: 16px;
}
.hero-subtitle {
    font-size: 1.2rem;
    color: rgba(255,255,255,0.7);
    margin-bottom: 40px;
}
.hero-search {
    display: flex;
    max-width: 520px;
    margin: 0 auto 48px;
    border-radius: 28px;
    overflow: hidden;
    box-shadow: 0 4px 24px rgba(0,122,255,0.3);
}
.hero-search input {
    flex: 1;
    padding: 14px 20px;
    border: none;
    font-size: 1rem;
    outline: none;
    background: #fff;
    color: var(--text);
}
.hero-search button {
    padding: 14px 28px;
    background: var(--blue);
    color: #fff;
    border: none;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
}
.hero-search button:hover {
    background: var(--blue-dark);
}
.hero-stats {
    display: flex;
    justify-content: center;
    gap: 48px;
}
.stat {
    display: flex;
    flex-direction: column;
}
.stat strong {
    font-size: 2rem;
    font-weight: 800;
}
.stat span {
    font-size: 0.9rem;
    color: rgba(255,255,255,0.6);
}

/* ========== Quick Links ========== */
.quick-links {
    padding: 48px 0 24px;
}
.quick-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
}
.quick-card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
    display: block;
    color: var(--text);
}
.quick-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    text-decoration: none;
}
.quick-card .icon {
    font-size: 2rem;
    display: block;
    margin-bottom: 8px;
}
.quick-card h3 {
    font-size: 1.05rem;
    font-weight: 600;
    margin-bottom: 4px;
}
.quick-card p {
    font-size: 0.85rem;
    color: var(--text-secondary);
}

/* ========== Guides ========== */
.guides {
    padding: 64px 0;
}
.guide-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
}
.guide-card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 28px;
    box-shadow: var(--shadow);
    border-left: 4px solid var(--blue);
    position: relative;
}
.guide-step {
    position: absolute;
    top: 20px;
    right: 24px;
    font-size: 1.2rem;
    font-weight: 800;
    color: var(--border);
}
.guide-card h3 {
    font-size: 1.15rem;
    font-weight: 700;
    margin-bottom: 16px;
    padding-right: 40px;
}
.guide-card ol {
    padding-left: 20px;
    color: var(--text-secondary);
    font-size: 0.93rem;
}
.guide-card ol li {
    margin-bottom: 8px;
}

/* ========== Issues ========== */
.issues {
    padding: 64px 0;
    background: var(--surface);
}
.issue-category {
    margin-bottom: 40px;
}
.issue-category h3 {
    font-size: 1.25rem;
    font-weight: 700;
    margin-bottom: 16px;
    padding-bottom: 8px;
    border-bottom: 2px solid var(--bg);
}
.issue-list {
    display: flex;
    flex-direction: column;
    gap: 8px;
}
.issue-item {
    background: var(--bg);
    border-radius: var(--radius);
    overflow: hidden;
}
.issue-item summary {
    padding: 16px 20px;
    font-weight: 600;
    cursor: pointer;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: background 0.2s;
}
.issue-item summary:hover {
    background: rgba(0,122,255,0.05);
}
.issue-item summary::after {
    content: '+';
    font-size: 1.3rem;
    font-weight: 400;
    color: var(--blue);
    transition: transform 0.2s;
    flex-shrink: 0;
    margin-left: 12px;
}
.issue-item[open] summary::after {
    content: '−';
    transform: rotate(180deg);
}
.issue-solution {
    padding: 0 20px 20px;
    font-size: 0.93rem;
    color: var(--text-secondary);
    line-height: 1.7;
}
.issue-solution p {
    margin-bottom: 8px;
}
.issue-solution ol,
.issue-solution ul {
    padding-left: 20px;
    margin-bottom: 8px;
}
.issue-solution li {
    margin-bottom: 4px;
}
.issue-solution strong {
    color: var(--text);
}
.issue-solution code {
    background: rgba(0,0,0,0.06);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.9em;
}

/* ========== FAQ ========== */
.faq {
    padding: 64px 0;
}
.faq-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 20px;
}
.faq-item {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
}
.faq-item h4 {
    font-size: 1.05rem;
    font-weight: 700;
    margin-bottom: 8px;
}
.faq-item p {
    font-size: 0.93rem;
    color: var(--text-secondary);
}

/* ========== Error Codes Table ========== */
.error-codes {
    padding: 64px 0;
    background: var(--surface);
}
.table-wrapper {
    overflow-x: auto;
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}
table {
    width: 100%;
    border-collapse: collapse;
    font-size: 0.93rem;
}
thead {
    background: var(--text);
    color: #fff;
}
th {
    padding: 14px 16px;
    text-align: left;
    font-weight: 600;
}
td {
    padding: 12px 16px;
    border-bottom: 1px solid var(--border);
}
tbody tr:hover {
    background: rgba(0,122,255,0.04);
}
td code {
    background: rgba(0,0,0,0.06);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.9em;
    white-space: nowrap;
}

/* ========== Resources ========== */
.resources {
    padding: 64px 0;
}
.resource-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 16px;
}
.resource-card {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
    transition: transform 0.2s, box-shadow 0.2s;
    display: block;
    color: var(--text);
}
.resource-card:hover {
    transform: translateY(-3px);
    box-shadow: var(--shadow-lg);
    text-decoration: none;
}
.resource-card h4 {
    font-size: 1.05rem;
    font-weight: 600;
    margin-bottom: 6px;
    color: var(--blue);
}
.resource-card p {
    font-size: 0.88rem;
    color: var(--text-secondary);
}

/* ========== Footer ========== */
.footer {
    background: #1D1D1F;
    color: #A1A1A6;
    padding: 48px 0 24px;
}
.footer-content {
    display: flex;
    gap: 48px;
    margin-bottom: 32px;
}
.footer-brand {
    max-width: 240px;
}
.footer-logo {
    font-size: 1.2rem;
    font-weight: 700;
    color: #fff;
    display: block;
    margin-bottom: 8px;
}
.footer-brand p {
    font-size: 0.88rem;
}
.footer-links {
    display: flex;
    gap: 48px;
    flex: 1;
}
.footer-col h4 {
    color: #fff;
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: 12px;
}
.footer-col a {
    display: block;
    font-size: 0.85rem;
    color: #A1A1A6;
    margin-bottom: 8px;
    transition: color 0.2s;
}
.footer-col a:hover {
    color: #fff;
    text-decoration: none;
}
.footer-bottom {
    border-top: 1px solid rgba(255,255,255,0.1);
    padding-top: 20px;
    text-align: center;
    font-size: 0.82rem;
}

/* ========== Back to Top ========== */
.back-to-top {
    position: fixed;
    bottom: 32px;
    right: 32px;
    width: 44px;
    height: 44px;
    border-radius: 50%;
    background: var(--blue);
    color: #fff;
    border: none;
    font-size: 1.4rem;
    cursor: pointer;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s, visibility 0.3s, transform 0.2s;
    z-index: 99;
}
.back-to-top.visible {
    opacity: 1;
    visibility: visible;
}
.back-to-top:hover {
    transform: scale(1.1);
}

/* ========== Search Overlay ========== */
.search-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.6);
    backdrop-filter: blur(4px);
    -webkit-backdrop-filter: blur(4px);
    z-index: 200;
    display: flex;
    align-items: flex-start;
    justify-content: center;
    padding-top: 80px;
}
.search-overlay[hidden] {
    display: none;
}
.search-overlay-content {
    background: var(--surface);
    border-radius: var(--radius);
    padding: 32px;
    width: 90%;
    max-width: 640px;
    max-height: 70vh;
    overflow-y: auto;
    box-shadow: var(--shadow-lg);
    position: relative;
}
.close-btn {
    position: absolute;
    top: 12px;
    right: 16px;
    background: none;
    border: none;
    font-size: 1.8rem;
    cursor: pointer;
    color: var(--text-secondary);
    line-height: 1;
}
.search-overlay-content h3 {
    margin-bottom: 16px;
}
.search-result-item {
    padding: 12px;
    border-bottom: 1px solid var(--border);
}
.search-result-item:last-child {
    border-bottom: none;
}
.search-result-item h4 {
    font-size: 1rem;
    margin-bottom: 4px;
}
.search-result-item p {
    font-size: 0.88rem;
    color: var(--text-secondary);
}
.no-results {
    text-align: center;
    color: var(--text-secondary);
    padding: 24px;
}

/* ========== Responsive ========== */
@media (max-width: 768px) {
    h2 {
        font-size: 1.6rem;
    }

    /* Nav */
    .nav-links {
        display: none;
        position: absolute;
        top: 56px;
        left: 0;
        right: 0;
        background: rgba(255,255,255,0.98);
        backdrop-filter: blur(20px);
        flex-direction: column;
        padding: 16px 24px;
        gap: 16px;
        border-bottom: 1px solid var(--border);
    }
    .nav-links.active {
        display: flex;
    }
    .hamburger {
        display: flex;
    }

    /* Hero */
    .hero {
        padding: 48px 24px 40px;
    }
    .hero h1 {
        font-size: 1.8rem;
    }
    .hero-subtitle {
        font-size: 1rem;
    }
    .hero-stats {
        gap: 24px;
    }
    .stat strong {
        font-size: 1.4rem;
    }

    /* Grids to single column */
    .quick-grid,
    .guide-grid,
    .faq-grid,
    .resource-grid {
        grid-template-columns: 1fr;
    }

    /* Footer */
    .footer-content {
        flex-direction: column;
        gap: 32px;
    }
    .footer-brand {
        max-width: 100%;
    }
    .footer-links {
        flex-wrap: wrap;
        gap: 24px;
    }

    /* Back to top */
    .back-to-top {
        bottom: 20px;
        right: 20px;
        width: 38px;
        height: 38px;
        font-size: 1.2rem;
    }
}

@media (max-width: 480px) {
    .hero h1 {
        font-size: 1.5rem;
    }
    .hero-search {
        flex-direction: column;
        border-radius: var(--radius);
    }
    .hero-search input {
        border-radius: var(--radius) var(--radius) 0 0;
        text-align: center;
    }
    .hero-search button {
        border-radius: 0 0 var(--radius) var(--radius);
    }
    .section-desc {
        margin-bottom: 32px;
        font-size: 0.95rem;
    }
}