@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700;800;900&display=swap');

:root {
    --royal-blue: #1976D2;
    --royal-blue-dark: #1565C0;
    --light-blue: #90CAF9;
    --field-blue: #E3F2FD;
    --card-white: #FFFFFF;
    --slate-gray: #263238;
    --silver: #B0BEC5;
    --white: #FFFFFF;
    --black: #000000;

    --primary: var(--royal-blue);
    --primary-dark: var(--royal-blue-dark);
    --secondary: var(--light-blue);
    --bg-soft: var(--field-blue);
    --text-main: var(--slate-gray);
    --text-muted: var(--silver);

    --radius-sm: 8px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --radius-xl: 32px;
    --shadow-sm: 0 2px 8px rgba(25, 118, 210, 0.06);
    --shadow-md: 0 4px 24px rgba(25, 118, 210, 0.08);
    --shadow-lg: 0 8px 40px rgba(25, 118, 210, 0.12);
    --shadow-xl: 0 16px 64px rgba(25, 118, 210, 0.16);
    --transition-fast: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: all 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

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

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: #F8FBFF;
    color: var(--text-main);
    line-height: 1.7;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* ═══════════════════════════════════════════
   HEADER / NAVIGATION
   ═══════════════════════════════════════════ */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(255, 255, 255, 0.85);
    backdrop-filter: blur(20px) saturate(180%);
    -webkit-backdrop-filter: blur(20px) saturate(180%);
    border-bottom: 1px solid rgba(25, 118, 210, 0.08);
    transition: var(--transition);
}

.header.scrolled {
    box-shadow: var(--shadow-md);
}

.nav {
    max-width: 1100px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo-group {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    text-decoration: none;
}

.logo-icon {
    width: 44px;
    height: 44px;
    border-radius: var(--radius-sm);
    object-fit: contain;
}

.logo-name {
    font-size: 1.5rem;
    font-weight: 800;
    color: var(--primary);
    letter-spacing: -0.5px;
}

.nav-links {
    display: flex;
    gap: 0.25rem;
    list-style: none;
}

.nav-links a {
    display: inline-block;
    padding: 0.5rem 1.25rem;
    border-radius: var(--radius-lg);
    color: var(--text-main);
    text-decoration: none;
    font-size: 0.875rem;
    font-weight: 500;
    transition: var(--transition-fast);
}

.nav-links a:hover {
    background: var(--field-blue);
    color: var(--primary);
}

.nav-links a.active {
    background: var(--primary);
    color: var(--white);
}

/* ═══════════════════════════════════════════
   HERO SECTION
   ═══════════════════════════════════════════ */
.hero {
    position: relative;
    min-height: 420px;
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    padding: 8rem 2rem 4rem;
    background: linear-gradient(135deg, #1565C0 0%, #1976D2 40%, #42A5F5 100%);
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: -20%;
    width: 600px;
    height: 600px;
    background: radial-gradient(circle, rgba(144, 202, 249, 0.3) 0%, transparent 70%);
    animation: float-orb 12s ease-in-out infinite;
}

.hero::after {
    content: '';
    position: absolute;
    bottom: -30%;
    right: -10%;
    width: 500px;
    height: 500px;
    background: radial-gradient(circle, rgba(255, 255, 255, 0.1) 0%, transparent 70%);
    animation: float-orb 10s ease-in-out infinite reverse;
}

@keyframes float-orb {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(30px, -40px) scale(1.05); }
    66% { transform: translate(-20px, 20px) scale(0.95); }
}

.hero-content {
    position: relative;
    z-index: 2;
    max-width: 700px;
}

.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.375rem 1rem;
    background: rgba(255, 255, 255, 0.15);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(255, 255, 255, 0.25);
    border-radius: var(--radius-lg);
    color: var(--white);
    font-size: 0.8rem;
    font-weight: 500;
    margin-bottom: 1.5rem;
    animation: fadeInDown 0.8s ease-out;
}

.hero-badge .dot {
    width: 6px;
    height: 6px;
    background: #69F0AE;
    border-radius: 50%;
    animation: pulse-dot 2s ease-in-out infinite;
}

@keyframes pulse-dot {
    0%, 100% { opacity: 1; transform: scale(1); }
    50% { opacity: 0.5; transform: scale(1.5); }
}

.hero h1 {
    font-size: 3rem;
    font-weight: 800;
    color: var(--white);
    line-height: 1.15;
    letter-spacing: -1px;
    margin-bottom: 1rem;
    animation: fadeInUp 0.8s ease-out 0.2s both;
}

.hero p {
    font-size: 1.1rem;
    color: rgba(255, 255, 255, 0.85);
    font-weight: 400;
    max-width: 520px;
    margin: 0 auto;
    animation: fadeInUp 0.8s ease-out 0.4s both;
}

.hero-wave {
    position: absolute;
    bottom: -1px;
    left: 0;
    right: 0;
    z-index: 3;
}

.hero-wave svg {
    display: block;
    width: 100%;
    height: 60px;
}

@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(24px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeInDown {
    from { opacity: 0; transform: translateY(-16px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ═══════════════════════════════════════════
   TABLE OF CONTENTS
   ═══════════════════════════════════════════ */
.toc {
    max-width: 1100px;
    margin: -2rem auto 0;
    padding: 0 2rem;
    position: relative;
    z-index: 10;
}

.toc-inner {
    background: var(--white);
    border-radius: var(--radius-lg);
    padding: 2rem 2.5rem;
    box-shadow: var(--shadow-lg);
    border: 1px solid rgba(25, 118, 210, 0.06);
    display: flex;
    align-items: center;
    gap: 2rem;
    flex-wrap: wrap;
}

.toc-label {
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--primary);
    white-space: nowrap;
}

.toc-links {
    display: flex;
    gap: 0.5rem;
    list-style: none;
    flex-wrap: wrap;
}

.toc-links a {
    display: inline-flex;
    align-items: center;
    gap: 0.375rem;
    padding: 0.375rem 0.875rem;
    border-radius: var(--radius-sm);
    color: var(--text-main);
    text-decoration: none;
    font-size: 0.8rem;
    font-weight: 500;
    background: var(--field-blue);
    transition: var(--transition-fast);
}

.toc-links a:hover {
    background: var(--primary);
    color: var(--white);
    transform: translateY(-2px);
    box-shadow: var(--shadow-sm);
}

.toc-links .toc-number {
    font-weight: 700;
    font-size: 0.7rem;
    opacity: 0.5;
}

/* ═══════════════════════════════════════════
   MAIN CONTENT
   ═══════════════════════════════════════════ */
.content {
    max-width: 1100px;
    margin: 0 auto;
    padding: 4rem 2rem;
}

.section-header {
    text-align: center;
    margin-bottom: 3rem;
    padding-top: 2rem;
}

.section-tag {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.375rem 1rem;
    background: var(--field-blue);
    border-radius: var(--radius-lg);
    color: var(--primary);
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    margin-bottom: 1rem;
}

.section-tag .tag-icon {
    font-size: 0.875rem;
}

.section-title {
    font-size: 2.25rem;
    font-weight: 800;
    color: var(--text-main);
    letter-spacing: -0.75px;
    line-height: 1.2;
    margin-bottom: 0.5rem;
}

.section-title span {
    color: var(--primary);
}

.section-subtitle {
    color: var(--text-muted);
    font-size: 0.95rem;
    font-weight: 400;
}

/* ═══════════════════════════════════════════
   ARTICLE CARDS
   ═══════════════════════════════════════════ */
.article-card {
    background: var(--white);
    border-radius: var(--radius-lg);
    padding: 2.5rem;
    margin-bottom: 1.5rem;
    box-shadow: var(--shadow-sm);
    border: 1px solid rgba(25, 118, 210, 0.06);
    transition: var(--transition);
    position: relative;
    overflow: hidden;
}

.article-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 4px;
    height: 100%;
    background: linear-gradient(180deg, var(--primary), var(--secondary));
    border-radius: 0 4px 4px 0;
    opacity: 0;
    transition: var(--transition);
}

.article-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(25, 118, 210, 0.12);
}

.article-card:hover::before {
    opacity: 1;
}

.article-number {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: var(--radius-sm);
    background: linear-gradient(135deg, var(--primary), #42A5F5);
    color: var(--white);
    font-size: 0.875rem;
    font-weight: 700;
    margin-bottom: 1rem;
    flex-shrink: 0;
}

.article-title {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--text-main);
    margin-bottom: 0.75rem;
    line-height: 1.4;
}

.article-text {
    color: #546E7A;
    font-size: 0.9375rem;
    line-height: 1.75;
    text-align: justify;
}

.article-text strong {
    color: var(--text-main);
    font-weight: 600;
}

/* List Styling */
.article-list {
    list-style: none;
    margin: 0.75rem 0;
    padding: 0;
}

.article-list li {
    position: relative;
    padding: 0.625rem 0 0.625rem 2rem;
    color: #546E7A;
    font-size: 0.9375rem;
    line-height: 1.65;
    border-bottom: 1px solid rgba(25, 118, 210, 0.04);
}

.article-list li:last-child {
    border-bottom: none;
}

.article-list li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background: linear-gradient(135deg, var(--primary), var(--secondary));
}

/* Highlight Box */
.highlight-box {
    background: linear-gradient(135deg, var(--field-blue), rgba(144, 202, 249, 0.15));
    border-radius: var(--radius-md);
    padding: 1.25rem 1.5rem;
    margin: 1rem 0;
    border-left: 3px solid var(--primary);
}

.highlight-box p {
    color: var(--text-main);
    font-size: 0.875rem;
    font-weight: 500;
    margin: 0;
}

/* ═══════════════════════════════════════════
   DIVIDER BETWEEN SECTIONS
   ═══════════════════════════════════════════ */
.section-divider {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    margin: 4rem 0;
    position: relative;
}

.section-divider::before,
.section-divider::after {
    content: '';
    flex: 1;
    height: 1px;
    background: linear-gradient(90deg, transparent, rgba(25, 118, 210, 0.15), transparent);
}

.section-divider .divider-icon {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--field-blue);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    color: var(--primary);
    border: 2px solid rgba(25, 118, 210, 0.1);
    flex-shrink: 0;
}

/* ═══════════════════════════════════════════
   FOOTER
   ═══════════════════════════════════════════ */
.footer {
    background: var(--slate-gray);
    color: var(--white);
    position: relative;
    overflow: hidden;
}

.footer::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--primary), var(--secondary), var(--primary));
    background-size: 200% 100%;
    animation: gradient-shift 4s ease-in-out infinite;
}

@keyframes gradient-shift {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

.footer-inner {
    max-width: 1100px;
    margin: 0 auto;
    padding: 3rem 2rem;
}

.footer-grid {
    display: grid;
    grid-template-columns: 2fr 1fr 1fr;
    gap: 3rem;
    margin-bottom: 2.5rem;
}

.footer-brand .footer-logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.footer-brand .footer-logo img {
    width: 36px;
    height: 36px;
    border-radius: 6px;
}

.footer-brand .footer-logo span {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--white);
}

.footer-brand p {
    color: var(--silver);
    font-size: 0.875rem;
    line-height: 1.6;
    max-width: 320px;
}

.footer-col h4 {
    font-size: 0.75rem;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 1.5px;
    color: var(--white);
    margin-bottom: 1rem;
}

.footer-col ul {
    list-style: none;
}

.footer-col ul li {
    margin-bottom: 0.5rem;
}

.footer-col ul a {
    color: var(--silver);
    text-decoration: none;
    font-size: 0.875rem;
    transition: var(--transition-fast);
}

.footer-col ul a:hover {
    color: var(--secondary);
    padding-left: 4px;
}

.footer-bottom {
    padding-top: 2rem;
    border-top: 1px solid rgba(255, 255, 255, 0.08);
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.footer-bottom p {
    color: var(--silver);
    font-size: 0.8rem;
}

.footer-bottom .footer-legal {
    display: flex;
    gap: 1.5rem;
}

.footer-bottom .footer-legal a {
    color: var(--silver);
    text-decoration: none;
    font-size: 0.8rem;
    transition: var(--transition-fast);
}

.footer-bottom .footer-legal a:hover {
    color: var(--secondary);
}

/* ═══════════════════════════════════════════
   SCROLL ANIMATIONS
   ═══════════════════════════════════════════ */
.reveal {
    opacity: 0;
    transform: translateY(30px);
    transition: opacity 0.6s cubic-bezier(0.4, 0, 0.2, 1),
                transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
}

.reveal.visible {
    opacity: 1;
    transform: translateY(0);
}

.reveal-delay-1 { transition-delay: 0.1s; }
.reveal-delay-2 { transition-delay: 0.2s; }
.reveal-delay-3 { transition-delay: 0.3s; }

/* ═══════════════════════════════════════════
   CUSTOM SCROLLBAR
   ═══════════════════════════════════════════ */
::-webkit-scrollbar {
    width: 8px;
}

::-webkit-scrollbar-track {
    background: #F0F4F8;
}

::-webkit-scrollbar-thumb {
    background: var(--secondary);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--primary);
}

/* ═══════════════════════════════════════════
   BACK TO TOP BUTTON
   ═══════════════════════════════════════════ */
.back-to-top {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background: var(--primary);
    color: var(--white);
    border: none;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.25rem;
    box-shadow: var(--shadow-lg);
    opacity: 0;
    visibility: hidden;
    transform: translateY(20px);
    transition: var(--transition);
    z-index: 999;
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.back-to-top:hover {
    background: var(--primary-dark);
    transform: translateY(-4px);
    box-shadow: var(--shadow-xl);
}

/* ═══════════════════════════════════════════
   RESPONSIVE
   ═══════════════════════════════════════════ */
@media (max-width: 768px) {
    .nav {
        padding: 0.75rem 1.25rem;
    }

    .nav-links {
        display: none;
    }

    .hero {
        min-height: 340px;
        padding: 7rem 1.5rem 3rem;
    }

    .hero h1 {
        font-size: 2rem;
    }

    .hero p {
        font-size: 0.95rem;
    }

    .toc {
        padding: 0 1.25rem;
    }

    .toc-inner {
        flex-direction: column;
        gap: 1rem;
        padding: 1.5rem;
        align-items: flex-start;
    }

    .content {
        padding: 3rem 1.25rem;
    }

    .article-card {
        padding: 1.75rem;
    }

    .section-title {
        font-size: 1.75rem;
    }

    .footer-grid {
        grid-template-columns: 1fr;
        gap: 2rem;
    }

    .footer-bottom {
        flex-direction: column;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .hero h1 {
        font-size: 1.625rem;
    }

    .article-card {
        padding: 1.25rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .toc-links {
        gap: 0.375rem;
    }

    .toc-links a {
        font-size: 0.7rem;
        padding: 0.3rem 0.625rem;
    }
}