/* =========================
           1. BIẾN MÀU VÀ CÀI ĐẶT CHUNG
        ========================== */
        :root {
            --red: #b40000;
            --dark-red: #7d0000;
            --light-red: #fff1f1;
            --yellow: #ffc928;
            --light-yellow: #fff8df;
            --black: #171717;
            --text: #333333;
            --gray: #6c6c6c;
            --light-gray: #f4f5f7;
            --white: #ffffff;
            --border: #e6e6e6;
            --green: #18864b;
            --blue: #1565c0;

            --shadow-small: 0 5px 18px rgba(0, 0, 0, 0.08);
            --shadow-medium: 0 12px 35px rgba(0, 0, 0, 0.13);
            --radius-small: 10px;
            --radius-medium: 18px;
            --radius-large: 28px;
        }

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

        html {
            scroll-behavior: smooth;
        }

        body {
            font-family:
                Arial,
                "Helvetica Neue",
                "Segoe UI",
                sans-serif;
            background: #fafafa;
            color: var(--text);
            line-height: 1.65;
        }

        img {
            max-width: 100%;
            display: block;
        }

        a {
            color: inherit;
            text-decoration: none;
        }

        button,
        input {
            font: inherit;
        }

        button {
            cursor: pointer;
        }

        .container {
            width: min(1180px, calc(100% - 32px));
            margin: 0 auto;
        }

        .skip-link {
            position: absolute;
            top: -50px;
            left: 15px;
            z-index: 9999;
            padding: 10px 18px;
            background: var(--yellow);
            color: var(--black);
            font-weight: 700;
            border-radius: 8px;
        }

        .skip-link:focus {
            top: 15px;
        }

        /* =========================
           2. HEADER
        ========================== */
        .site-header {
            position: sticky;
            top: 0;
            z-index: 1000;
            background: rgba(255, 255, 255, 0.96);
            border-bottom: 1px solid var(--border);
            box-shadow: 0 3px 15px rgba(0, 0, 0, 0.05);
            backdrop-filter: blur(12px);
        }

        .header-inner {
            min-height: 74px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 25px;
        }

        .logo {
            display: flex;
            align-items: center;
            gap: 12px;
            flex-shrink: 0;
        }

        .logo-icon {
            width: 48px;
            height: 48px;
            display: grid;
            place-items: center;
            border-radius: 14px;
            background: linear-gradient(145deg, var(--red), var(--dark-red));
            color: var(--yellow);
            font-weight: 900;
            font-size: 22px;
            box-shadow: 0 6px 18px rgba(180, 0, 0, 0.25);
        }

        .logo-text strong {
            display: block;
            color: var(--red);
            font-size: 20px;
            line-height: 1.1;
        }

        .logo-text span {
            color: var(--gray);
            font-size: 12px;
        }

        .main-nav {
            display: flex;
            align-items: center;
            gap: 8px;
        }

        .main-nav a {
            padding: 10px 13px;
            color: var(--text);
            font-size: 14px;
            font-weight: 700;
            border-radius: 9px;
            transition: 0.25s ease;
        }

        .main-nav a:hover,
        .main-nav a.active {
            color: var(--red);
            background: var(--light-red);
        }

        .menu-button {
            display: none;
            width: 44px;
            height: 44px;
            border: 0;
            border-radius: 10px;
            background: var(--light-red);
            color: var(--red);
            font-size: 23px;
        }

        /* =========================
           3. HERO
        ========================== */
        .hero {
            position: relative;
            overflow: hidden;
            padding: 75px 0 65px;
            background:
                radial-gradient(
                    circle at 85% 20%,
                    rgba(255, 201, 40, 0.35),
                    transparent 28%
                ),
                radial-gradient(
                    circle at 10% 90%,
                    rgba(255, 255, 255, 0.14),
                    transparent 32%
                ),
                linear-gradient(135deg, #7e0000 0%, #b40000 60%, #dc1d1d 100%);
            color: var(--white);
        }

        .hero::before {
            content: "学";
            position: absolute;
            right: 7%;
            top: -75px;
            font-size: 330px;
            line-height: 1;
            font-weight: 900;
            color: rgba(255, 255, 255, 0.055);
            pointer-events: none;
        }

        .hero-grid {
            position: relative;
            z-index: 2;
            display: grid;
            grid-template-columns: 1.25fr 0.75fr;
            align-items: center;
            gap: 55px;
        }

        .hero-badge {
            display: inline-flex;
            align-items: center;
            gap: 8px;
            margin-bottom: 18px;
            padding: 7px 15px;
            background: var(--yellow);
            color: var(--black);
            border-radius: 999px;
            font-size: 13px;
            font-weight: 800;
        }

        .hero h1 {
            max-width: 760px;
            margin-bottom: 18px;
            font-size: clamp(34px, 6vw, 60px);
            line-height: 1.15;
            letter-spacing: -1.5px;
        }

        .hero h1 span {
            color: var(--yellow);
        }

        .hero-description {
            max-width: 720px;
            color: rgba(255, 255, 255, 0.9);
            font-size: 18px;
        }

        .hero-actions {
            display: flex;
            flex-wrap: wrap;
            gap: 13px;
            margin-top: 28px;
        }

        .btn {
            min-height: 48px;
            display: inline-flex;
            align-items: center;
            justify-content: center;
            gap: 8px;
            padding: 11px 21px;
            border: 2px solid transparent;
            border-radius: 12px;
            font-weight: 800;
            transition: 0.25s ease;
        }

        .btn-primary {
            background: var(--yellow);
            color: var(--black);
        }

        .btn-primary:hover {
            background: #ffdc6a;
            transform: translateY(-2px);
        }

        .btn-outline {
            border-color: rgba(255, 255, 255, 0.65);
            color: var(--white);
        }

        .btn-outline:hover {
            background: var(--white);
            color: var(--red);
        }

        .hero-card {
            padding: 25px;
            background: rgba(255, 255, 255, 0.13);
            border: 1px solid rgba(255, 255, 255, 0.24);
            border-radius: var(--radius-large);
            backdrop-filter: blur(10px);
            box-shadow: var(--shadow-medium);
        }

        .hero-card h2 {
            margin-bottom: 17px;
            font-size: 21px;
            color: var(--yellow);
        }

        .hero-stat-list {
            display: grid;
            gap: 12px;
        }

        .hero-stat {
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 15px;
            padding: 13px 15px;
            background: rgba(255, 255, 255, 0.1);
            border-radius: 12px;
        }

        .hero-stat strong {
            color: var(--yellow);
            font-size: 22px;
        }

        .hero-stat span {
            color: rgba(255, 255, 255, 0.88);
            font-size: 14px;
        }

        /* =========================
           4. BREADCRUMB
        ========================== */
        .breadcrumb {
            padding: 15px 0;
            background: var(--white);
            border-bottom: 1px solid var(--border);
        }

        .breadcrumb ol {
            display: flex;
            flex-wrap: wrap;
            gap: 8px;
            list-style: none;
            font-size: 14px;
            color: var(--gray);
        }

        .breadcrumb li:not(:last-child)::after {
            content: "/";
            margin-left: 8px;
            color: #aaa;
        }

        .breadcrumb a:hover {
            color: var(--red);
        }

        /* =========================
           5. TỔNG QUAN LỘ TRÌNH
        ========================== */
        .overview {
            padding: 65px 0 25px;
        }

        .section-heading {
            max-width: 760px;
            margin: 0 auto 35px;
            text-align: center;
        }

        .section-label {
            display: inline-block;
            margin-bottom: 9px;
            color: var(--red);
            font-size: 13px;
            font-weight: 900;
            letter-spacing: 1.2px;
            text-transform: uppercase;
        }

        .section-heading h2 {
            margin-bottom: 12px;
            color: var(--black);
            font-size: clamp(28px, 4vw, 40px);
            line-height: 1.25;
        }

        .section-heading p {
            color: var(--gray);
            font-size: 16px;
        }

        .overview-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 18px;
        }

        .overview-card {
            padding: 24px;
            background: var(--white);
            border: 1px solid var(--border);
            border-radius: var(--radius-medium);
            box-shadow: var(--shadow-small);
            transition: 0.25s ease;
        }

        .overview-card:hover {
            transform: translateY(-5px);
            box-shadow: var(--shadow-medium);
        }

        .overview-icon {
            width: 52px;
            height: 52px;
            display: grid;
            place-items: center;
            margin-bottom: 16px;
            border-radius: 15px;
            background: var(--light-red);
            font-size: 25px;
        }

        .overview-card:nth-child(2) .overview-icon {
            background: var(--light-yellow);
        }

        .overview-card:nth-child(3) .overview-icon {
            background: #eaf5ff;
        }

        .overview-card:nth-child(4) .overview-icon {
            background: #eaf9f0;
        }

        .overview-card h3 {
            margin-bottom: 7px;
            color: var(--black);
            font-size: 18px;
        }

        .overview-card p {
            color: var(--gray);
            font-size: 14px;
        }

        /* =========================
           6. THANH TÌM KIẾM
        ========================== */
        .search-section {
            padding: 40px 0 25px;
        }

        .search-box {
            max-width: 850px;
            margin: 0 auto;
            padding: 18px;
            display: flex;
            align-items: center;
            gap: 12px;
            background: var(--white);
            border: 1px solid var(--border);
            border-radius: 18px;
            box-shadow: var(--shadow-small);
        }

        .search-icon {
            padding-left: 5px;
            color: var(--red);
            font-size: 22px;
        }

        .search-box input {
            width: 100%;
            min-width: 0;
            padding: 11px 5px;
            border: 0;
            outline: 0;
            color: var(--text);
            font-size: 16px;
        }

        .search-box input::placeholder {
            color: #999;
        }

        .clear-search {
            display: none;
            padding: 8px 13px;
            border: 0;
            border-radius: 8px;
            background: var(--light-gray);
            color: var(--gray);
            font-weight: 700;
        }

        .search-result-text {
            min-height: 26px;
            margin-top: 14px;
            text-align: center;
            color: var(--gray);
            font-size: 14px;
        }

        /* =========================
           7. THANH LỌC GIAI ĐOẠN
        ========================== */
        .filter-section {
            padding: 10px 0 35px;
        }

        .filter-buttons {
            display: flex;
            flex-wrap: wrap;
            justify-content: center;
            gap: 10px;
        }

        .filter-button {
            padding: 10px 17px;
            border: 1px solid var(--border);
            border-radius: 999px;
            background: var(--white);
            color: var(--text);
            font-weight: 800;
            transition: 0.2s ease;
        }

        .filter-button:hover,
        .filter-button.active {
            border-color: var(--red);
            background: var(--red);
            color: var(--white);
        }

        /* =========================
           8. DANH SÁCH BÀI HỌC
        ========================== */
        .lessons {
            padding: 20px 0 75px;
        }

        .stage-section {
            margin-bottom: 55px;
            scroll-margin-top: 95px;
        }

        .stage-header {
            margin-bottom: 23px;
            padding: 24px 26px;
            display: flex;
            justify-content: space-between;
            align-items: center;
            gap: 20px;
            background:
                linear-gradient(
                    130deg,
                    rgba(180, 0, 0, 0.08),
                    rgba(255, 201, 40, 0.15)
                );
            border-left: 6px solid var(--red);
            border-radius: 14px;
        }

        .stage-header h2 {
            margin-bottom: 5px;
            color: var(--red);
            font-size: 25px;
        }

        .stage-header p {
            color: var(--gray);
            font-size: 14px;
        }

        .stage-number {
            flex-shrink: 0;
            padding: 8px 14px;
            background: var(--yellow);
            color: var(--black);
            border-radius: 999px;
            font-size: 13px;
            font-weight: 900;
        }

        .lesson-grid {
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            gap: 20px;
        }

        .lesson-card {
            position: relative;
            overflow: hidden;
            min-height: 255px;
            display: flex;
            flex-direction: column;
            background: var(--white);
            border: 1px solid var(--border);
            border-radius: var(--radius-medium);
            box-shadow: var(--shadow-small);
            transition: 0.25s ease;
        }

        .lesson-card::before {
            content: "";
            position: absolute;
            top: 0;
            left: 0;
            width: 5px;
            height: 100%;
            background: var(--red);
            transition: 0.25s ease;
        }

        .lesson-card:hover {
            border-color: rgba(180, 0, 0, 0.3);
            transform: translateY(-6px);
            box-shadow: var(--shadow-medium);
        }

        .lesson-card:hover::before {
            width: 8px;
        }

        .lesson-card-content {
            flex: 1;
            padding: 23px 23px 17px 28px;
        }

        .lesson-top {
            margin-bottom: 13px;
            display: flex;
            align-items: flex-start;
            justify-content: space-between;
            gap: 12px;
        }

        .lesson-number {
            display: inline-flex;
            align-items: center;
            padding: 5px 11px;
            background: var(--light-red);
            color: var(--red);
            border-radius: 999px;
            font-size: 12px;
            font-weight: 900;
        }

        .lesson-icon {
            font-size: 28px;
        }

        .lesson-card h3 {
            margin-bottom: 9px;
            color: var(--black);
            font-size: 20px;
            line-height: 1.35;
        }

        .lesson-card h3 a:hover {
            color: var(--red);
        }

        .lesson-card p {
            color: var(--gray);
            font-size: 14px;
        }

        .lesson-tags {
            margin-top: 15px;
            display: flex;
            flex-wrap: wrap;
            gap: 6px;
        }

        .lesson-tags span {
            padding: 4px 8px;
            background: var(--light-gray);
            color: #555;
            border-radius: 6px;
            font-size: 11px;
            font-weight: 700;
        }

        .lesson-card-footer {
            padding: 14px 22px 17px 28px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 12px;
            border-top: 1px solid #f0f0f0;
        }

        .lesson-status {
            color: var(--green);
            font-size: 12px;
            font-weight: 800;
        }

        .lesson-link {
            display: inline-flex;
            align-items: center;
            gap: 6px;
            color: var(--red);
            font-size: 14px;
            font-weight: 900;
        }

        .lesson-link:hover {
            gap: 10px;
        }

        .final-card {
            background:
                radial-gradient(
                    circle at top right,
                    rgba(255, 201, 40, 0.22),
                    transparent 35%
                ),
                var(--white);
            border: 2px solid var(--yellow);
        }

        .final-card::before {
            background: var(--yellow);
        }

        .no-results {
            display: none;
            margin: 10px auto 60px;
            max-width: 620px;
            padding: 35px;
            text-align: center;
            background: var(--white);
            border: 1px dashed #d1d1d1;
            border-radius: var(--radius-medium);
        }

        .no-results strong {
            display: block;
            margin-bottom: 8px;
            color: var(--black);
            font-size: 21px;
        }

        .hidden {
            display: none !important;
        }

        /* =========================
           9. LỢI ÍCH
        ========================== */
        .benefits {
            padding: 70px 0;
            background: var(--black);
            color: var(--white);
        }

        .benefits .section-heading h2 {
            color: var(--white);
        }

        .benefits .section-heading p {
            color: rgba(255, 255, 255, 0.7);
        }

        .benefit-grid {
            display: grid;
            grid-template-columns: repeat(4, 1fr);
            gap: 18px;
        }

        .benefit-card {
            padding: 25px;
            background: rgba(255, 255, 255, 0.07);
            border: 1px solid rgba(255, 255, 255, 0.12);
            border-radius: var(--radius-medium);
        }

        .benefit-card span {
            display: block;
            margin-bottom: 13px;
            font-size: 30px;
        }

        .benefit-card h3 {
            margin-bottom: 8px;
            color: var(--yellow);
            font-size: 18px;
        }

        .benefit-card p {
            color: rgba(255, 255, 255, 0.7);
            font-size: 14px;
        }

        /* =========================
           10. FAQ
        ========================== */
        .faq {
            padding: 75px 0;
        }

        .faq-list {
            max-width: 850px;
            margin: 0 auto;
            display: grid;
            gap: 13px;
        }

        .faq-item {
            overflow: hidden;
            background: var(--white);
            border: 1px solid var(--border);
            border-radius: 13px;
        }

        .faq-question {
            width: 100%;
            padding: 18px 20px;
            display: flex;
            justify-content: space-between;
            gap: 15px;
            border: 0;
            background: var(--white);
            color: var(--black);
            text-align: left;
            font-weight: 800;
        }

        .faq-question:hover {
            color: var(--red);
        }

        .faq-answer {
            display: none;
            padding: 0 20px 20px;
            color: var(--gray);
            font-size: 15px;
        }

        .faq-item.open .faq-answer {
            display: block;
        }

        .faq-symbol {
            color: var(--red);
            font-size: 20px;
            line-height: 1;
        }

        /* =========================
           11. CTA
        ========================== */
        .cta-section {
            padding: 20px 0 75px;
        }

        .cta-box {
            padding: 45px;
            display: flex;
            align-items: center;
            justify-content: space-between;
            gap: 30px;
            background:
                radial-gradient(
                    circle at 80% 20%,
                    rgba(255, 201, 40, 0.25),
                    transparent 25%
                ),
                linear-gradient(135deg, var(--dark-red), var(--red));
            color: var(--white);
            border-radius: var(--radius-large);
            box-shadow: var(--shadow-medium);
        }

        .cta-box h2 {
            margin-bottom: 8px;
            font-size: 30px;
        }

        .cta-box p {
            max-width: 680px;
            color: rgba(255, 255, 255, 0.8);
        }

        /* =========================
           12. FOOTER
        ========================== */
        .site-footer {
            padding: 30px 0 20px;
            background: #0f0f0f;
            color: rgba(255, 255, 255, 0.7);
        }

        .footer-grid {
            display: grid;
            grid-template-columns: 1.3fr 1fr 1fr 1fr;
            gap: 35px;
        }

        .footer-brand {
            max-width: 300px;
        }

        .footer-logo {
            margin-bottom: 15px;
            display: inline-flex;
        }

        .footer-title {
            margin-bottom: 13px;
            color: var(--white);
            font-size: 17px;
        }

        .footer-links {
            list-style: none;
            display: grid;
            gap: 9px;
        }

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

        .footer-bottom {
            margin-top: 40px;
            padding-top: 18px;
            text-align: center;
            border-top: 1px solid rgba(255, 255, 255, 0.1);
            font-size: 13px;
        }
        .footer{
      padding:55px 0 25px;color:rgba(255,255,255,.72);background:var(--black);
    }
    .footer-grid{display:grid;grid-template-columns:1.5fr repeat(3,1fr);gap:35px}
    .footer h3{color:white;margin-bottom:13px}
    .footer p,.footer a{font-size:12px}
    .footer a{display:block;margin-bottom:8px}
    .footer a:hover{color:var(--yellow)}
    .copyright{margin-top:35px;padding-top:20px;border-top:1px solid rgba(255,255,255,.1);text-align:center;font-size:11px}


        /* =========================
           13. NÚT LÊN ĐẦU TRANG
        ========================== */
        .back-to-top {
            position: fixed;
            right: 20px;
            bottom: 20px;
            z-index: 800;
            width: 46px;
            height: 46px;
            display: none;
            place-items: center;
            border: 0;
            border-radius: 50%;
            background: var(--red);
            color: var(--white);
            font-size: 20px;
            box-shadow: var(--shadow-medium);
        }

        .back-to-top.show {
            display: grid;
        }

        /* =========================
           14. RESPONSIVE
        ========================== */
        @media (max-width: 1000px) {
            .hero-grid {
                grid-template-columns: 1fr;
            }

            .hero-card {
                max-width: 650px;
            }

            .overview-grid,
            .benefit-grid {
                grid-template-columns: repeat(2, 1fr);
            }

            .lesson-grid {
                grid-template-columns: repeat(2, 1fr);
            }

            .footer-grid {
                grid-template-columns: repeat(2, 1fr);
            }
        }

        @media (max-width: 820px) {
            .menu-button {
                display: block;
            }

            .main-nav {
                position: absolute;
                top: 74px;
                left: 0;
                right: 0;
                display: none;
                padding: 15px 16px 20px;
                flex-direction: column;
                align-items: stretch;
                background: var(--white);
                border-bottom: 1px solid var(--border);
                box-shadow: var(--shadow-small);
            }

            .main-nav.open {
                display: flex;
            }

            .main-nav a {
                padding: 12px 15px;
            }

            .cta-box {
                align-items: flex-start;
                flex-direction: column;
            }
        }

        @media (max-width: 650px) {
            .container {
                width: min(100% - 22px, 1180px);
            }

            .hero {
                padding: 55px 0 50px;
            }

            .hero h1 {
                font-size: 36px;
            }

            .hero-description {
                font-size: 16px;
            }

            .hero-actions {
                align-items: stretch;
                flex-direction: column;
            }

            .btn {
                width: 100%;
            }

            .overview-grid,
            .lesson-grid,
            .benefit-grid,
            .footer-grid {
                grid-template-columns: 1fr;
            }

            .stage-header {
                align-items: flex-start;
                flex-direction: column;
            }

            .search-box {
                padding: 12px;
            }

            .search-icon {
                display: none;
            }

            .clear-search {
                padding: 7px 9px;
                font-size: 12px;
            }

            .cta-box {
                padding: 30px 23px;
            }

            .cta-box h2 {
                font-size: 25px;
            }
        }
    
        /* =========================
           LOGO ẢNH ST CHINESE
           Chỉ thay phần hiển thị logo, giữ nguyên bố cục trang
        ========================== */
        .logo-image {
            width: 64px;
            height: 64px;
            display: block;
            object-fit: contain;
            flex-shrink: 0;
        }

        .footer-logo-image {
            width: 210px;
            height: auto;
            max-width: 100%;
            border-radius: 14px;
        }

        @media (max-width: 650px) {
            .logo-image {
                width: 58px;
                height: 58px;
            }

            .footer-logo-image {
                width: 180px;
                height: auto;
            }
        }