@import url('https://fonts.googleapis.com/css2?family=Poppins:wght@400;500;700;900&display=swap');
    :root { --primary: #2563eb; --bg: #f1f5f9; --text: #0f172a; }
    body { font-family: 'Poppins', sans-serif; background: var(--bg); color: var(--text); margin: 0; padding: 0; }
    .container { max-width: 600px; margin: 0 auto; min-height: 100vh; display: flex; flex-direction: column; background: #ffffff; }
    a { text-decoration: none; color: inherit; transition: color 0.2s; }
    .top-bar { display: flex; justify-content: space-between; align-items: center; padding: 15px 20px; border-bottom: 2px solid #f1f5f9; background: #fff; position: sticky; top: 0; z-index: 50; }
    .brand { font-weight: 900; font-size: 1.4rem; color: var(--primary); letter-spacing: -0.5px; }
    .top-icons { display: flex; align-items: center; gap: 15px; }
    .search-toggle-icon { font-size: 1.2rem; color: #475569; cursor: pointer; padding: 5px; }
    .premium-badge { background: linear-gradient(135deg, #fbbf24, #f59e0b); color: white; padding: 6px 12px; border-radius: 20px; font-size: 0.8rem; font-weight: 700; cursor: pointer; }
    .home-search-container { background: #f8fafc; padding: 15px 20px; border-bottom: 2px solid #e2e8f0; }
    .hidden { display: none; }
    .tagline { text-align: center; color: #64748b; font-size: 0.95rem; margin: 20px 20px 15px; font-weight: 500; }
    .content-area { padding: 20px; flex: 1; }
    .home-filters { display: flex; gap: 10px; margin-bottom: 15px; }
    .home-select, .filter-select { flex: 1; padding: 12px; border-radius: 10px; border: 2px solid #e2e8f0; font-weight: 600; background: white; font-family: inherit; -webkit-appearance: none; }
    .search-wrap { position: relative; margin-bottom: 20px; }
    .search-input { width: 100%; padding: 14px 45px 14px 15px; border: 2px solid #e2e8f0; border-radius: 12px; font-size: 1rem; box-sizing: border-box; font-family: inherit; }
    .search-icon { position: absolute; right: 15px; top: 14px; font-size: 1.1rem; color: #94a3b8; }
    .filter-panel { background: #f8fafc; padding: 15px; border-radius: 16px; margin-bottom: 20px; border: 1px solid #e2e8f0; }
    .filter-row { display: flex; gap: 10px; margin-bottom: 10px; flex-wrap: wrap; }
    .reset-btn { width: 100%; padding: 12px; background: #cbd5e1; color: #475569; border: none; border-radius: 10px; font-weight: 700; cursor: pointer; margin-top: 5px; }
    .active-tags { margin-bottom: 10px; }
    .tag-chip { background: #e0f2fe; color: #0284c7; padding: 6px 12px; border-radius: 20px; font-size: 0.8rem; font-weight: 700; margin-right:5px; display: inline-block; margin-bottom: 5px;}
    .sub-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
    .sub-card { background: white; padding: 20px; border-radius: 16px; border: 2px solid #f1f5f9; text-align: center; display: block; font-weight: 700; transition: all 0.2s; }
    .sub-card:active { transform: scale(0.98); background: #f8fafc; }
    .card { background: white; padding: 25px; border-radius: 20px; margin-bottom: 25px; border: 2px solid #f1f5f9; position: relative; }
    .meta-badge { display: inline-block; background:#f1f5f9; color:#475569; padding:4px 10px; border-radius:6px; font-size:0.8rem; font-weight:600; margin-bottom: 15px; }
    #q-text { font-size: 1.15rem; line-height: 1.6; color: #334155; margin-bottom: 25px; }
    .theory-container { display: none; margin-top: 25px; position: relative; border-radius: 16px; overflow: hidden; border: 2px solid #bbf7d0; }
    .theory-content { background: #f0fdf4; padding: 25px; color: #166534; line-height: 1.7; }
    .blurred { filter: blur(8px); pointer-events: none; opacity: 0.6; }
    .lock-overlay { position: absolute; top: 0; left: 0; width: 100%; height: 100%; display: flex; flex-direction: column; align-items: center; justify-content: center; background: rgba(255,255,255,0.8); z-index: 10; backdrop-filter: blur(4px); }
    .modal-backdrop { display: none; position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0,0,0,0.8); z-index: 2000; align-items: center; justify-content: center; backdrop-filter: blur(5px); padding: 20px; box-sizing: border-box; }
    .modal { background: white; padding: 30px; border-radius: 24px; width: 100%; max-width: 350px; text-align: center; animation: popUp 0.3s ease-out; }
    @keyframes popUp { from { transform: scale(0.8); opacity: 0; } to { transform: scale(1); opacity: 1; } }
    .btn { display: block; width: 100%; padding: 18px; margin: 12px 0; border: 2px solid #f1f5f9; background: #f8fafc; border-radius: 14px; font-size: 1rem; cursor: pointer; text-align: left; font-weight: 500; color: #334155; transition: all 0.2s; }
    .correct { background: #dcfce7 !important; border-color: #86efac !important; color: #166534 !important; font-weight: 700; }
    .wrong { background: #fee2e2 !important; border-color: #fca5a5 !important; color: #991b1b !important; }
    .unlock-btn { background: var(--primary); color: white; border: none; padding: 14px 24px; border-radius: 30px; font-weight: 700; cursor: pointer; margin-top: 10px; width: 100%; font-size: 1rem; }
    .close-modal { margin-top: 12px; background: transparent; color: #64748b; border: 2px solid #e2e8f0; padding: 12px 20px; border-radius: 30px; font-weight: 700; cursor: pointer; width: 100%; }
    .yt-btn { width: 100%; margin-top: 25px; margin-bottom: 25px; padding: 15px; background: #fff; border: 2px solid #ef4444; color: #ef4444; font-weight: 700; border-radius: 14px; cursor: pointer; display: flex; align-items: center; justify-content: center; gap: 10px; font-size: 1rem; }
    .nav-box { display: flex; justify-content: space-between; margin-top: 30px; gap: 12px; }
    .nav-btn { background: var(--primary); color: white; padding: 15px; border-radius: 14px; font-weight: 700; width: 48%; text-align: center; }
    .disabled { background: #cbd5e1; pointer-events: none; opacity: 0.5; }
    .share-grid { display: flex; gap: 10px; margin-top: 30px; padding-top: 25px; border-top: 2px dashed #e2e8f0; }
    .share-btn { flex: 1; padding: 12px; border: none; border-radius: 10px; color: white; font-size: 0.85rem; font-weight: 700; cursor: pointer; text-align: center; }
    .load-more-btn { display: block; width: 100%; padding: 16px; background: #f1f5f9; color: #334155; border: none; border-radius: 14px; font-weight: 700; margin-top: 25px; cursor: pointer; text-align: center; font-size: 1rem; }
    .site-footer { margin-top: auto; text-align: center; background: #f8fafc; padding: 30px 20px; border-top: 1px solid #e2e8f0; }
    .footer-links { margin-bottom: 15px; display: flex; justify-content: center; gap: 20px; flex-wrap: wrap; }
    .footer-links a { color: #475569; font-weight: 600; font-size: 0.9rem; }
    .footer-vip { color: #d97706; font-weight: 800; }
    .pricing-card { border: 2px solid #fbbf24; border-radius: 20px; padding: 30px; text-align: center; background: #fffbeb; }
    .price-tag { font-size: 2.5rem; font-weight: 800; color: #d97706; margin: 10px 0; }
    .plan-box { background: white; border-radius:16px; padding:20px; border:2px solid #e2e8f0; margin-bottom:12px; text-align:left; display:flex; justify-content:space-between; align-items:center; }