:root {
    --bg-main: #121212;
    --bg-card: #1f1f1f;
    --accent: #ff9900;
    --accent-glow: rgba(255, 153, 0, 0.15);
    --text-main: #ffffff;
    --text-sec: #aaaaaa;
}

* { margin: 0; padding: 0; box-sizing: border-box; font-family: 'Inter', system-ui, sans-serif; }

body { background-color: var(--bg-main); color: var(--text-main); min-height: 100vh; display: flex; flex-direction: column; overflow-x: hidden; }

/* --- Navbar --- */
nav { background-color: rgba(0,0,0,0.9); padding: 15px 0; border-bottom: 1px solid #333; position: sticky; top: 0; z-index: 100; backdrop-filter: blur(10px); }
.container { max-width: -webkit-fill-available; margin: 0 auto; padding: 0 20px; }
.nav-content { display: flex; justify-content: space-between; align-items: center; }

.logo { font-size: 24px; font-weight: bold; display: flex; align-items: center; }
.white-text { color: #fff; margin-right: 2px; }
.orange-box { color: #fff; padding: 0px 6px; border-radius: 4px; font-weight: 800; }

.search-bar { flex: 1; max-width: 400px; display: flex; background: #222; border-radius: 6px; border: 1px solid #333; margin: 0 20px; }
.search-bar input { width: 100%; background: transparent; border: none; color: #fff; padding: 10px; outline: none; }
.search-bar button { background: transparent; border: none; color: #888; padding: 0 15px; cursor: pointer; }

.nav-actions { display: flex; gap: 15px; align-items: center; }
.premium-btn { background: #222; color: var(--accent); border: 1px solid var(--accent); padding: 8px 16px; border-radius: 4px; font-weight: 600; cursor: pointer; transition: 0.3s; }
.premium-btn:hover { background: var(--accent); color: #000; }
.user-icon { font-size: 24px; cursor: pointer; padding: 5px; }

/* --- Mobile Menu Toggle --- */
.mobile-only { display: none; }
.menu-toggle { background: none; border: none; color: #fff; font-size: 24px; cursor: pointer; }

/* Mobile Slide-out Menu */
.mobile-menu {
    position: fixed; top: 0; right: -100%; width: 280px; height: 100%;
    background: #000; border-left: 1px solid #333; z-index: 1000;
    transition: 0.3s ease-in-out; display: flex; flex-direction: column;
}
.mobile-menu.active { right: 0; }
.mobile-menu-header { padding: 20px; display: flex; justify-content: space-between; align-items: center; border-bottom: 1px solid #333; }
.close-btn { background: none; border: none; color: #fff; font-size: 24px; cursor: pointer; }
.mobile-menu-content { padding: 20px; }
.mobile-link { display: block; color: #fff; text-decoration: none; padding: 12px 0; font-size: 16px; border-bottom: 1px solid #222; }
.mobile-link:hover { color: var(--accent); padding-left: 5px; }
.mobile-search { display: flex; background: #222; padding: 5px; border-radius: 4px; margin-bottom: 20px; }
.mobile-search input { width: 100%; background: none; border: none; color: #fff; padding: 5px; outline: none; }
.mobile-search button { background: none; border: none; color: #888; }
.full-width { width: 100%; text-align: center; padding: 12px; }

/* --- NEW Hero Section (Replaces Bento) --- */
.hero-banner {
    position: relative;
    padding: 80px 0;
    margin-bottom: 40px;
    text-align: center;
    background: radial-gradient(circle at center, #1a1a1a 0%, #121212 70%);
    border-bottom: 1px solid #222;
    overflow: hidden;
}
.hero-content { position: relative; z-index: 2; max-width: 800px; margin: 0 auto; }
.hero-badge {
    display: inline-block;
    background: #222; color: var(--accent); border: 1px solid #333;
    padding: 6px 14px; border-radius: 20px; font-size: 13px; font-weight: bold;
    margin-bottom: 20px; text-transform: uppercase; letter-spacing: 1px;
}
.hero-banner h1 { font-size: 48px; line-height: 1.1; margin-bottom: 20px; font-weight: 800; }
.highlight { color: var(--accent); }
.hero-banner p { font-size: 18px; color: var(--text-sec); margin-bottom: 30px; line-height: 1.6; padding: 0 20px; }
.hero-buttons { display: flex; justify-content: center; align-items: center; gap: 30px; }
.cta-primary {
    background: var(--accent); color: #000; font-size: 16px; font-weight: bold;
    padding: 14px 30px; border-radius: 6px; border: none; cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
}
.cta-primary:hover { transform: translateY(-2px); box-shadow: 0 10px 20px rgba(255,153,0,0.3); }
.hero-stat { font-size: 14px; text-align: left; border-left: 3px solid #333; padding-left: 15px; }
.stat-number { display: block; font-size: 20px; font-weight: bold; color: #fff; }
.stat-label { color: #666; font-size: 12px; text-transform: uppercase; }

/* Background Glow Effect */
.hero-glow {
    position: absolute; top: 50%; left: 50%; transform: translate(-50%, -50%);
    width: 600px; height: 400px; background: var(--accent);
    filter: blur(150px); opacity: 0.08; z-index: 1; pointer-events: none;
}

/* --- Subject Filter Tabs --- */
.subject-tabs-container { border-bottom: 1px solid #333; margin-bottom: 30px; }
.subject-tabs { display: flex; gap: 30px; overflow-x: auto; -webkit-overflow-scrolling: touch; }
.subject-tabs::-webkit-scrollbar { display: none; }
.tab-btn {
    background: transparent; border: none; color: #888; font-size: 16px;
    padding: 10px 0; cursor: pointer; position: relative; white-space: nowrap;
    transition: 0.3s;
}
.tab-btn:hover { color: #fff; }
.tab-btn.active { color: #fff; font-weight: bold; }
.tab-btn.active::after { content: ''; position: absolute; bottom: -1px; left: 0; width: 100%; height: 3px; background-color: var(--accent); }

/* --- Book Grid --- */
.section-header h2 { font-size: 22px; font-weight: normal; margin-bottom: 20px; border-left: 4px solid var(--accent); padding-left: 10px; }
.book-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 20px; }
.book-card { background: var(--bg-card); border-radius: 8px; overflow: hidden; transition: 0.3s; cursor: pointer; border: 1px solid #2a2a2a; }
.book-card:hover { transform: translateY(-5px); border-color: #444; box-shadow: 0 10px 30px rgba(0,0,0,0.5); }
.book-thumb { height: 180px; overflow: hidden; position: relative; }
.book-thumb img { width: 100%; height: 100%; object-fit: cover; }
.book-info { padding: 15px; }
.book-title { font-size: 16px; margin-bottom: 5px; color: #fff; font-weight: 600; line-height: 1.4; }
.book-meta { font-size: 12px; color: var(--text-sec); margin-bottom: 15px; display: flex; justify-content: space-between; }
.price-row { display: flex; justify-content: space-between; align-items: center; border-top: 1px solid #333; padding-top: 12px; }
.price { color: var(--accent); font-size: 18px; font-weight: bold; }
.buy-btn { background: #333; color: #fff; border: none; padding: 6px 15px; border-radius: 4px; cursor: pointer; font-size: 12px; font-weight: bold; transition: 0.2s; }
.buy-btn:hover { background: var(--accent); color: #000; }

/* --- Footer --- */
.site-footer { background-color: #000; padding: 60px 0 30px 0; border-top: 1px solid #222; margin-top: auto; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr 1fr; gap: 40px; }
.footer-col h4 { color: #fff; margin-bottom: 20px; font-size: 16px; }
.footer-col p { color: #666; font-size: 14px; line-height: 1.6; max-width: 300px; }
.footer-col a { display: block; color: #888; text-decoration: none; margin-bottom: 10px; font-size: 14px; transition: 0.2s; }
.footer-col a:hover { color: var(--accent); padding-left: 5px; }
.social-icons a { margin-right: 15px; font-size: 20px; }

/* --- Modal --- */
.modal-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.9); z-index: 2000; display: none; align-items: center; justify-content: center; backdrop-filter: blur(5px); }
.modal-overlay.active { display: flex; animation: fadeIn 0.2s; }
.modal-container { background: #1a1a1a; width: 90%; max-width: 450px; border-radius: 12px; border: 1px solid #333; }
.modal-header { padding: 15px 20px; border-bottom: 1px solid #333; display: flex; justify-content: space-between; align-items: center; }
.modal-header button { background: none; border: none; color: #fff; font-size: 24px; cursor: pointer; }
.modal-body { padding: 25px; }
.item-summary { display: flex; gap: 15px; background: #111; padding: 10px; border-radius: 8px; margin-bottom: 20px; align-items: center; border: 1px solid #222; }
.item-summary img { width: 50px; height: 70px; object-fit: cover; border-radius: 4px; }
.input-group { margin-bottom: 15px; }
.input-group label { display: block; font-size: 12px; color: #888; margin-bottom: 5px; }
.input-group input { width: 100%; padding: 12px; background: #0f0f0f; border: 1px solid #333; color: #fff; border-radius: 6px; outline: none; }
.input-group input:focus { border-color: var(--accent); }
.cta-btn { width: 100%; background: var(--accent); color: #000; font-weight: bold; border: none; padding: 14px; border-radius: 6px; cursor: pointer; font-size: 16px; transition: 0.2s; }
.cta-btn:hover { background: #e68a00; }
.info-note { background: #222; padding: 10px; font-size: 12px; color: #aaa; border-radius: 6px; margin-bottom: 15px; display: flex; gap: 10px; align-items: center; }
.success-box { text-align: center; padding: 30px 0; color: #fff; }
.success-box i { font-size: 50px; color: #4CAF50; margin-bottom: 15px; display: block; }

/* --- Mobile Responsiveness --- */
@media (max-width: 768px) {
    .desktop-only { display: none !important; }
    .mobile-only { display: block; }
    
    .hero-banner { padding: 50px 0; text-align: left; }
    .hero-banner h1 { font-size: 36px; }
    .hero-buttons { flex-direction: column; align-items: flex-start; gap: 20px; }
    .hero-stat { border-left: none; padding-left: 0; border-top: 1px solid #333; padding-top: 10px; width: 100%; }
    
    .book-grid { grid-template-columns: 1fr; }
    .footer-grid { grid-template-columns: 1fr; gap: 30px; }
}

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