/* ===== CSS Custom Properties ===== */
:root {
    --color-primary: #2563eb;
    --color-primary-dark: #1d4ed8;
    --color-primary-light: #dbeafe;
    --color-text: #1f2937;
    --color-text-light: #6b7280;
    --color-bg: #ffffff;
    --color-bg-alt: #f9fafb;
    --color-border: #e5e7eb;

    --font-body: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-mono: 'SF Mono', SFMono-Regular, Consolas, 'Liberation Mono', Menlo, monospace;

    --space-xs: 0.25rem;
    --space-sm: 0.5rem;
    --space-md: 1rem;
    --space-lg: 2rem;
    --space-xl: 4rem;

    --container-max: 1140px;
    --radius: 8px;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.1), 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px rgba(0, 0, 0, 0.1), 0 4px 6px rgba(0, 0, 0, 0.05);
}

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

/* ===== Base ===== */
html {
    font-size: 16px;
    -webkit-text-size-adjust: 100%;
}

body {
    font-family: var(--font-body);
    color: var(--color-text);
    background: var(--color-bg);
    line-height: 1.6;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

a {
    color: var(--color-primary);
    text-decoration: none;
}

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

/* ===== Typography ===== */
h1, h2, h3, h4, h5, h6 {
    line-height: 1.3;
    margin-bottom: var(--space-md);
    color: var(--color-text);
}

h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.25rem; }

p {
    margin-bottom: var(--space-md);
}

ul, ol {
    margin-bottom: var(--space-md);
    padding-left: var(--space-lg);
}

li {
    margin-bottom: var(--space-xs);
}

pre, code {
    font-family: var(--font-mono);
    font-size: 0.9em;
}

pre {
    background: var(--color-bg-alt);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: var(--space-md);
    overflow-x: auto;
    margin-bottom: var(--space-md);
}

code {
    background: var(--color-bg-alt);
    padding: 0.1em 0.3em;
    border-radius: 3px;
}

pre code {
    background: none;
    padding: 0;
}

blockquote {
    border-left: 4px solid var(--color-primary);
    padding-left: var(--space-md);
    margin-bottom: var(--space-md);
    color: var(--color-text-light);
    font-style: italic;
}

table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: var(--space-md);
}

th, td {
    text-align: left;
    padding: var(--space-sm) var(--space-md);
    border-bottom: 1px solid var(--color-border);
}

th {
    font-weight: 600;
    background: var(--color-bg-alt);
}

/* ===== Layout ===== */
.container {
    max-width: var(--container-max);
    margin: 0 auto;
    padding: 0 var(--space-md);
}

.site-content {
    flex: 1;
    padding: var(--space-xl) 0;
}

/* ===== Header ===== */
.site-header {
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    position: sticky;
    top: 0;
    z-index: 100;
}

.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
}

.site-logo {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    font-weight: 700;
    font-size: 1.2rem;
    color: var(--color-text);
    text-decoration: none;
}

.site-logo:hover {
    color: var(--color-primary);
    text-decoration: none;
}

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

.main-nav ul {
    display: flex;
    list-style: none;
    gap: var(--space-sm);
    margin: 0;
    padding: 0;
}

.main-nav a {
    display: block;
    padding: var(--space-sm) var(--space-md);
    color: var(--color-text-light);
    border-radius: var(--radius);
    font-size: 0.95rem;
    transition: color 0.2s, background 0.2s;
}

.main-nav a:hover,
.main-nav a.active {
    color: var(--color-primary);
    background: var(--color-primary-light);
    text-decoration: none;
}

/* Mobile nav toggle */
.mobile-nav-toggle {
    display: none;
    background: none;
    border: none;
    cursor: pointer;
    padding: var(--space-sm);
    flex-direction: column;
    gap: 5px;
}

.mobile-nav-toggle span {
    display: block;
    width: 24px;
    height: 2px;
    background: var(--color-text);
    transition: transform 0.3s, opacity 0.3s;
}

/* ===== Hero ===== */
.hero {
    text-align: center;
    padding: var(--space-xl) 0;
    margin-bottom: var(--space-xl);
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: var(--space-sm);
}

.hero-tagline {
    font-size: 1.25rem;
    color: var(--color-text-light);
    margin-bottom: var(--space-lg);
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

.hero-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
    display: inline-block;
    padding: 0.75rem 1.5rem;
    border-radius: var(--radius);
    font-weight: 600;
    font-size: 1rem;
    text-decoration: none;
    transition: background 0.2s, transform 0.1s;
    cursor: pointer;
    border: none;
}

.btn:hover {
    text-decoration: none;
    transform: translateY(-1px);
}

.btn-primary {
    background: var(--color-primary);
    color: #fff;
}

.btn-primary:hover {
    background: var(--color-primary-dark);
    color: #fff;
}

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

.btn-secondary:hover {
    background: var(--color-border);
    color: var(--color-text);
}

/* ===== Cards ===== */
.card-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: var(--space-lg);
    margin-bottom: var(--space-xl);
}

.card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: var(--space-lg);
    box-shadow: var(--shadow);
    transition: box-shadow 0.2s, transform 0.2s;
}

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

.card h3 {
    margin-bottom: var(--space-sm);
}

.card p {
    color: var(--color-text-light);
    font-size: 0.95rem;
}

/* ===== Features ===== */
.features {
    margin-bottom: var(--space-xl);
}

.feature-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--space-md);
}

.feature-item {
    padding: var(--space-md);
    border-radius: var(--radius);
    background: var(--color-bg-alt);
}

.feature-item h3 {
    font-size: 1rem;
    margin-bottom: var(--space-xs);
}

.feature-item p {
    font-size: 0.9rem;
    color: var(--color-text-light);
    margin-bottom: 0;
}

/* ===== FAQ Accordion ===== */
.faq-list {
    max-width: 800px;
}

.faq-item {
    border-bottom: 1px solid var(--color-border);
}

.faq-item summary {
    padding: var(--space-md) 0;
    cursor: pointer;
    font-weight: 600;
    list-style: none;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.faq-item summary::after {
    content: '+';
    font-size: 1.5rem;
    color: var(--color-text-light);
    transition: transform 0.2s;
}

.faq-item[open] summary::after {
    content: '\2212';
}

.faq-item summary::-webkit-details-marker {
    display: none;
}

.faq-answer {
    padding: 0 0 var(--space-md);
    color: var(--color-text-light);
}

/* ===== Post/Article List ===== */
.post-list {
    list-style: none;
    padding: 0;
}

.post-list li {
    padding: var(--space-md) 0;
    border-bottom: 1px solid var(--color-border);
}

.post-list a {
    font-weight: 600;
    font-size: 1.1rem;
}

.post-date {
    display: block;
    font-size: 0.85rem;
    color: var(--color-text-light);
    margin-top: var(--space-xs);
}

/* ===== Article Content ===== */
.article-header {
    margin-bottom: var(--space-lg);
}

.article-header h1 {
    margin-bottom: var(--space-sm);
}

.article-header time {
    font-size: 0.9rem;
    color: var(--color-text-light);
}

.article-body {
    max-width: 70ch;
}

.article-body img {
    border-radius: var(--radius);
    margin: var(--space-md) 0;
}

/* ===== Prev/Next Navigation ===== */
.prev-next-nav {
    display: flex;
    justify-content: space-between;
    gap: var(--space-md);
    margin-top: var(--space-xl);
    padding-top: var(--space-lg);
    border-top: 1px solid var(--color-border);
}

.prev-next-nav a {
    display: block;
    padding: var(--space-md);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    max-width: 45%;
    transition: border-color 0.2s;
}

.prev-next-nav a:hover {
    border-color: var(--color-primary);
    text-decoration: none;
}

.prev-next-nav .label {
    display: block;
    font-size: 0.8rem;
    color: var(--color-text-light);
    margin-bottom: var(--space-xs);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.prev-next-nav .next {
    text-align: right;
    margin-left: auto;
}

/* ===== Download Section ===== */
.download-section {
    background: var(--color-bg-alt);
    border-radius: var(--radius);
    padding: var(--space-xl);
    text-align: center;
    margin: var(--space-xl) 0;
}

.download-section h2 {
    margin-bottom: var(--space-sm);
}

.download-section p {
    color: var(--color-text-light);
    margin-bottom: var(--space-lg);
}

.download-actions {
    display: flex;
    gap: var(--space-md);
    justify-content: center;
    flex-wrap: wrap;
}

/* ===== Product Cards ===== */
.product-card {
    display: flex;
    gap: var(--space-md);
    align-items: flex-start;
}

.product-card img {
    width: 64px;
    height: 64px;
    border-radius: var(--radius);
    flex-shrink: 0;
}

/* ===== Footer ===== */
.site-footer {
    background: var(--color-bg-alt);
    border-top: 1px solid var(--color-border);
    padding: var(--space-lg) 0;
    text-align: center;
    color: var(--color-text-light);
    font-size: 0.9rem;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .mobile-nav-toggle {
        display: flex;
    }

    .main-nav {
        display: none;
        position: absolute;
        top: 64px;
        left: 0;
        right: 0;
        background: var(--color-bg);
        border-bottom: 1px solid var(--color-border);
        box-shadow: var(--shadow-lg);
    }

    .main-nav.open {
        display: block;
    }

    .main-nav ul {
        flex-direction: column;
        padding: var(--space-md);
    }

    .hero h1 {
        font-size: 1.8rem;
    }

    .hero-tagline {
        font-size: 1.1rem;
    }

    .card-grid {
        grid-template-columns: 1fr;
    }

    .prev-next-nav {
        flex-direction: column;
    }

    .prev-next-nav a {
        max-width: 100%;
    }

    .prev-next-nav .next {
        text-align: left;
    }
}

@media (min-width: 1024px) {
    h1 { font-size: 2.5rem; }
    h2 { font-size: 1.75rem; }

    .hero h1 {
        font-size: 3rem;
    }
}