/* ===========================
   CSS Reset & Base
   =========================== */

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

:root {
    --bg-primary: #0a0a0f;
    --bg-secondary: #12121a;
    --bg-card: #1a1a25;
    --bg-card-hover: #222233;
    --bg-code: #0d0d14;
    --text-primary: #e8e8f0;
    --text-secondary: #8888a0;
    --text-muted: #555570;
    --accent-1: #6366f1;
    --accent-2: #8b5cf6;
    --accent-3: #a855f7;
    --green: #22c55e;
    --yellow: #eab308;
    --red: #ef4444;
    --orange: #f97316;
    --cyan: #22d3ee;
    --border: #2a2a3a;
    --radius: 12px;
    --radius-sm: 8px;
    --transition: 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.7;
    min-height: 100vh;
    overflow-x: hidden;
}

a {
    color: var(--accent-1);
    text-decoration: none;
    transition: color var(--transition);
}

a:hover {
    color: var(--accent-3);
}

img {
    max-width: 100%;
}

/* ===========================
   Navigation
   =========================== */

nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 1000;
    background: rgba(10, 10, 15, 0.8);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-bottom: 1px solid var(--border);
}

.nav-inner {
    max-width: 1200px;
    margin: 0 auto;
    padding: 16px 24px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.5px;
}

.nav-links {
    display: flex;
    gap: 24px;
}

.nav-links a {
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    transition: color var(--transition);
}

.nav-links a:hover,
.nav-links a.active {
    color: var(--text-primary);
}

/* ===========================
   Hero Section
   =========================== */

.hero {
    padding: 120px 24px 80px;
    text-align: center;
    background: linear-gradient(180deg, 
        rgba(99, 102, 241, 0.08) 0%,
        rgba(139, 92, 246, 0.04) 50%,
        transparent 100%
    );
    position: relative;
    overflow: hidden;
}

.hero::before {
    content: '';
    position: absolute;
    top: -50%;
    left: 50%;
    transform: translateX(-50%);
    width: 800px;
    height: 800px;
    background: radial-gradient(circle, rgba(99, 102, 241, 0.06) 0%, transparent 70%);
    pointer-events: none;
}

.hero-content {
    max-width: 800px;
    margin: 0 auto;
    position: relative;
    z-index: 1;
}

.hero-badge {
    display: inline-block;
    padding: 6px 16px;
    background: rgba(99, 102, 241, 0.15);
    border: 1px solid rgba(99, 102, 241, 0.3);
    border-radius: 100px;
    font-size: 13px;
    font-weight: 600;
    color: var(--accent-1);
    margin-bottom: 24px;
    letter-spacing: 0.5px;
    text-transform: uppercase;
}

.hero h1 {
    font-size: 56px;
    font-weight: 800;
    letter-spacing: -2px;
    line-height: 1.1;
    margin-bottom: 20px;
}

.gradient-text {
    background: linear-gradient(135deg, var(--accent-1), var(--accent-2), var(--accent-3));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero p {
    font-size: 18px;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto 40px;
    line-height: 1.7;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 48px;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat-num {
    font-size: 36px;
    font-weight: 800;
    color: var(--text-primary);
    line-height: 1;
}

.stat-label {
    font-size: 13px;
    color: var(--text-muted);
    font-weight: 500;
    margin-top: 4px;
    text-transform: uppercase;
    letter-spacing: 1px;
}

/* ===========================
   Rooms Section
   =========================== */

.rooms-section {
    max-width: 1200px;
    margin: 0 auto;
    padding: 60px 24px;
}

.section-header {
    text-align: center;
    margin-bottom: 48px;
}

.section-header h2 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 8px;
}

.section-header p {
    color: var(--text-secondary);
    font-size: 16px;
}

.rooms-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
    gap: 20px;
}

/* ===========================
   Room Cards
   =========================== */

.room-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 28px;
    cursor: pointer;
    transition: all var(--transition);
    position: relative;
    overflow: hidden;
}

.room-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(90deg, var(--accent-1), var(--accent-3));
    opacity: 0;
    transition: opacity var(--transition);
}

.room-card:hover {
    background: var(--bg-card-hover);
    border-color: rgba(99, 102, 241, 0.3);
    transform: translateY(-4px);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.3);
}

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

.room-card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 12px;
}

.room-card h3 {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.3px;
}

.difficulty-badge {
    display: inline-flex;
    align-items: center;
    padding: 3px 10px;
    border-radius: 100px;
    font-size: 11px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    flex-shrink: 0;
}

.difficulty-badge.easy {
    background: rgba(34, 197, 94, 0.15);
    color: var(--green);
    border: 1px solid rgba(34, 197, 94, 0.25);
}

.difficulty-badge.medium {
    background: rgba(249, 115, 22, 0.15);
    color: var(--orange);
    border: 1px solid rgba(249, 115, 22, 0.25);
}

.difficulty-badge.hard {
    background: rgba(239, 68, 68, 0.15);
    color: var(--red);
    border: 1px solid rgba(239, 68, 68, 0.25);
}

.room-card-flags {
    font-size: 13px;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.room-card-flags strong {
    color: var(--yellow);
}

.room-card-tech {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.tech-tag {
    padding: 3px 8px;
    background: rgba(99, 102, 241, 0.08);
    border: 1px solid rgba(99, 102, 241, 0.15);
    border-radius: 4px;
    font-size: 11px;
    color: var(--accent-1);
    font-weight: 500;
}

/* ===========================
   Writeup Detail View
   =========================== */

.writeup-section {
    max-width: 800px;
    margin: 0 auto;
    padding: 60px 24px;
}

.writeup-section.hidden {
    display: none;
}

.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition);
    margin-bottom: 32px;
    font-family: 'Inter', sans-serif;
}

.back-btn:hover {
    background: var(--bg-card-hover);
    color: var(--text-primary);
    border-color: rgba(99, 102, 241, 0.3);
}

/* ===========================
   Writeup Content Styles
   =========================== */

#writeupContent h1 {
    font-size: 36px;
    font-weight: 800;
    letter-spacing: -1.5px;
    margin-bottom: 8px;
    line-height: 1.2;
}

#writeupContent .writeup-meta {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
    margin-bottom: 32px;
}

#writeupContent .meta-item {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 4px 12px;
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 100px;
    font-size: 13px;
    color: var(--text-secondary);
}

#writeupContent .meta-item strong {
    color: var(--text-primary);
}

#writeupContent hr {
    border: none;
    border-top: 1px solid var(--border);
    margin: 32px 0;
}

#writeupContent h2 {
    font-size: 26px;
    font-weight: 700;
    margin: 40px 0 16px;
    letter-spacing: -0.5px;
    padding-bottom: 8px;
    border-bottom: 2px solid var(--border);
    color: var(--text-primary);
}

#writeupContent h3 {
    font-size: 20px;
    font-weight: 600;
    margin: 28px 0 12px;
    color: var(--accent-1);
}

#writeupContent p {
    margin-bottom: 16px;
    color: var(--text-secondary);
    line-height: 1.8;
}

#writeupContent strong {
    color: var(--text-primary);
}

#writeupContent ul, 
#writeupContent ol {
    margin: 12px 0 20px;
    padding-left: 24px;
}

#writeupContent li {
    margin-bottom: 8px;
    color: var(--text-secondary);
    line-height: 1.7;
}

#writeupContent table {
    width: 100%;
    border-collapse: separate;
    border-spacing: 0;
    margin: 16px 0 24px;
    border-radius: var(--radius-sm);
    overflow: hidden;
    border: 1px solid var(--border);
}

#writeupContent th {
    background: var(--bg-card);
    padding: 10px 16px;
    text-align: left;
    font-size: 13px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.5px;
    color: var(--text-muted);
    border-bottom: 1px solid var(--border);
}

#writeupContent td {
    padding: 10px 16px;
    font-size: 14px;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border);
}

#writeupContent tr:last-child td {
    border-bottom: none;
}

#writeupContent code {
    font-family: 'JetBrains Mono', monospace;
    background: rgba(99, 102, 241, 0.1);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 13px;
    color: var(--cyan);
}

#writeupContent pre {
    background: var(--bg-code);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 20px 24px;
    margin: 16px 0 24px;
    overflow-x: auto;
    position: relative;
}

#writeupContent pre code {
    background: none;
    padding: 0;
    color: var(--text-primary);
    font-size: 13px;
    line-height: 1.7;
    font-family: 'JetBrains Mono', monospace;
}

/* ===========================
   Flags Table in Writeup
   =========================== */

#writeupContent .flags-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 12px;
    margin: 16px 0 24px;
}

#writeupContent .flag-card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 16px;
    text-align: center;
}

#writeupContent .flag-card .flag-num {
    font-size: 24px;
    font-weight: 800;
    color: var(--accent-1);
    display: block;
}

#writeupContent .flag-card .flag-desc {
    font-size: 13px;
    color: var(--text-secondary);
    margin-top: 4px;
}

/* ===========================
   Key Takeaways Block
   =========================== */

#writeupContent .takeaways {
    background: rgba(99, 102, 241, 0.06);
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: var(--radius-sm);
    padding: 24px;
    margin: 24px 0;
}

#writeupContent .takeaways h3 {
    color: var(--accent-1);
    margin-top: 0;
}

#writeupContent .takeaways ul {
    margin-bottom: 0;
}

#writeupContent .takeaways li {
    color: var(--text-secondary);
}

/* ===========================
   Chain Block
   =========================== */

#writeupContent .chain {
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 8px;
    margin: 16px 0 24px;
}

#writeupContent .chain-step {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    padding: 8px 14px;
    font-size: 13px;
    color: var(--text-secondary);
}

#writeupContent .chain-arrow {
    color: var(--accent-1);
    font-size: 16px;
    font-weight: 600;
}

#writeupContent .chain-step.current {
    border-color: var(--accent-1);
    color: var(--accent-1);
    background: rgba(99, 102, 241, 0.1);
}

/* ===========================
   Footer
   =========================== */

footer {
    text-align: center;
    padding: 40px 24px;
    border-top: 1px solid var(--border);
    color: var(--text-muted);
    font-size: 14px;
}

footer a {
    color: var(--text-secondary);
}

footer a:hover {
    color: var(--accent-1);
}

/* ===========================
   Animations
   =========================== */

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.room-card {
    animation: fadeInUp 0.5s ease forwards;
    opacity: 0;
}

.room-card:nth-child(1) { animation-delay: 0.05s; }
.room-card:nth-child(2) { animation-delay: 0.10s; }
.room-card:nth-child(3) { animation-delay: 0.15s; }
.room-card:nth-child(4) { animation-delay: 0.20s; }
.room-card:nth-child(5) { animation-delay: 0.25s; }
.room-card:nth-child(6) { animation-delay: 0.30s; }
.room-card:nth-child(7) { animation-delay: 0.35s; }

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

#writeupSection {
    animation: fadeIn 0.3s ease;
}

/* ===========================
   Responsive
   =========================== */

@media (max-width: 768px) {
    .hero h1 {
        font-size: 36px;
    }
    .hero-stats {
        gap: 24px;
    }
    .stat-num {
        font-size: 28px;
    }
    .rooms-grid {
        grid-template-columns: 1fr;
    }
    #writeupContent h1 {
        font-size: 26px;
    }
    #writeupContent h2 {
        font-size: 20px;
    }
    #writeupContent pre {
        padding: 14px 16px;
    }
    .nav-inner {
        padding: 12px 16px;
    }
    .hero {
        padding: 100px 16px 60px;
    }
}

@media (max-width: 480px) {
    .hero h1 {
        font-size: 28px;
    }
    .hero-stats {
        flex-wrap: wrap;
        gap: 16px;
    }
    .room-card {
        padding: 20px;
    }
}