/* Reset & Base */
:root {
    --primary: #1e40af; /* Blue 800 */
    --primary-light: #3b82f6; /* Blue 500 */
    --primary-dark: #1e3a8a; /* Blue 900 */
    --accent: #eff6ff; /* Blue 50 */
    --text-main: #1f2937; /* Gray 800 */
    --text-secondary: #4b5563; /* Gray 600 */
    --text-light: #9ca3af; /* Gray 400 */
    --bg-page: #f8fafc; /* Slate 50 */
    --bg-card: #ffffff;
    --border: #e2e8f0; /* Slate 200 */
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -1px rgb(0 0 0 / 0.06);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -2px rgb(0 0 0 / 0.05);
}

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    line-height: 1.7;
    color: var(--text-main);
    background-color: var(--bg-page);
    -webkit-font-smoothing: antialiased;
    font-size: 16px;
}

/* Typography Overrides */
h1, h2, h3 {
    color: var(--text-main);
    letter-spacing: -0.025em;
}

h1 {
    font-size: 2.75rem;
    font-weight: 800;
    line-height: 1.2;
    margin-bottom: 1rem;
    background: linear-gradient(to right, var(--primary-dark), var(--primary-light));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

h2 {
    font-size: 1.75rem;
    margin-top: 3rem;
    margin-bottom: 1.5rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border);
    position: relative;
}

h2::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    width: 60px;
    height: 3px;
    background-color: var(--primary);
    border-radius: 2px;
}

h3 {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--primary-dark);
}

p, li {
    color: var(--text-secondary);
}

a {
    color: var(--primary);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.2s ease;
    border-bottom: 1px solid transparent;
}

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

/* Header */
header {
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border);
    position: sticky;
    top: 0;
    z-index: 50;
    box-shadow: var(--shadow-sm);
}

.header-container {
    max-width: 1000px;
    margin: 0 auto;
    padding: 1.25rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-weight: 800;
    font-size: 1.25rem;
    color: var(--primary-dark);
    letter-spacing: -0.02em;
}

.nav-link {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-left: 2rem;
    font-weight: 600;
}

.nav-link:hover {
    color: var(--primary);
    border-bottom-color: transparent;
}

/* Hero */
.hero {
    background: linear-gradient(135deg, white 0%, var(--bg-page) 100%);
    padding: 5rem 1.5rem 6rem;
    text-align: center;
    border-bottom: 1px solid var(--border);
}

.hero-content {
    max-width: 700px;
    margin: 0 auto;
}

.hero-content p {
    font-size: 1.25rem;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* Main Content Wrapper */
main {
    padding: 0 1.5rem 4rem;
}

/* Central Card */
.content-card {
    background-color: var(--bg-card);
    max-width: 900px;
    margin: -4rem auto 0;
    padding: 4rem;
    border-radius: 1.5rem;
    box-shadow: var(--shadow-lg);
    border: 1px solid var(--border);
    position: relative;
    z-index: 10;
}

/* TOC */
.toc {
    background-color: var(--bg-page);
    padding: 2rem;
    border-radius: 1rem;
    margin-bottom: 4rem;
    border: 1px solid var(--border);
}

.toc ul {
    list-style: none;
    padding: 0;
    margin: 0;
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 1rem 2rem;
}

.toc a {
    color: var(--text-secondary);
    font-size: 0.95rem;
    display: flex;
    align-items: center;
    border: none;
}

.toc a::before {
    content: '→';
    margin-right: 0.5rem;
    color: var(--primary-light);
    opacity: 0;
    transition: all 0.2s;
}

.toc a:hover {
    color: var(--primary);
    transform: translateX(5px);
}

.toc a:hover::before {
    opacity: 1;
}

/* Callouts */
.callouts {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 2rem;
    margin-bottom: 4rem;
}

.callout {
    background: white;
    border: 1px solid var(--border);
    padding: 2rem;
    border-radius: 1rem;
    text-align: center;
    transition: transform 0.2s, box-shadow 0.2s;
    box-shadow: var(--shadow-sm);
}

.callout:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-md);
    border-color: var(--primary-light);
}

.callout h3 {
    color: var(--primary);
    margin-bottom: 0.75rem;
    font-size: 1.1rem;
}

/* Lists */
ul {
    padding-left: 1.25rem;
}

li {
    margin-bottom: 0.75rem;
    line-height: 1.6;
}

/* Contact Box */
.contact-box {
    background-color: var(--accent);
    padding: 2rem;
    border-radius: 1rem;
    border: 1px solid #bfdbfe;
    margin-top: 1.5rem;
}

.contact-box p {
    color: var(--primary-dark);
    font-weight: 500;
}

.last-update {
    margin-top: 3rem;
    font-size: 0.9rem;
    color: var(--text-light);
    text-align: center;
    border-top: 1px solid var(--border);
    padding-top: 1.5rem;
}

/* Footer */
footer {
    background-color: white;
    border-top: 1px solid var(--border);
    padding: 3rem 1.5rem;
    text-align: center;
}

.footer-content {
    max-width: 800px;
    margin: 0 auto;
}

.footer-links {
    margin-top: 1.5rem;
}

.footer-links a {
    margin: 0 1rem;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.footer-links a:hover {
    color: var(--primary);
}

/* Mobile */
@media (max-width: 768px) {
    h1 {
        font-size: 2rem;
    }
    
    .content-card {
        padding: 2rem;
        margin-top: -2rem;
    }
    
    .header-container {
        flex-direction: column;
        gap: 1rem;
    }
    
    .nav-link {
        margin: 0 0.75rem;
    }

    .toc ul {
        grid-template-columns: 1fr;
    }
}