:root {
            --primary: #004e9a;
            --accent: #e74c3c;
            --bg: #f8f9fa;
            --text: #333;
            --white: #fff;
            --shadow: 0 5px 15px rgba(0, 0, 0, 0.08);
        }

        * {
            box-sizing: border-box;
        }

        html,
        body {
            font-family: 'Montserrat', sans-serif;
            background: var(--bg);
            color: var(--text);
            margin: 0;
            min-height: 100vh;
            display: flex;
            flex-direction: column;
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
            touch-action: pan-x pan-y;
            overscroll-behavior: none;
        }

        .navbar,
        .hero,
        .container {
            width: 100%;
        }

        .plyr input[type="range"],
        .plyr__controls {
            -webkit-user-select: auto !important;
            -moz-user-select: auto !important;
            -ms-user-select: auto !important;
            user-select: auto !important;
            z-index: 10000 !important;
        }

        a {
            text-decoration: none;
            color: inherit;
            transition: 0.3s;
        }

        ul {
            list-style: none;
            padding: 0;
            margin: 0;
        }

        /* PLAYER CUSTOM UI */
        .seek-overlay-btn {
            position: absolute;
            top: 50%;
            transform: translateY(-50%);
            background: rgba(0, 0, 0, 0.2);
            backdrop-filter: blur(4px);
            -webkit-backdrop-filter: blur(4px);
            border: 1px solid rgba(255, 255, 255, 0.1);
            color: white;
            border-radius: 50%;
            width: 32px;
            height: 32px;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            z-index: 2147483647;
            transition: opacity 0.3s ease, transform 0.2s ease;
            font-size: 0.65rem;
            font-weight: 600;
            opacity: 1;
            pointer-events: auto;
        }

        .seek-overlay-btn:active {
            transform: translateY(-50%) scale(0.9);
            background: rgba(0, 0, 0, 0.9);
        }

        .seek-btn-left {
            left: 15%;
        }

        .seek-btn-right {
            right: 15%;
        }

        .status-overlay-btn {
            position: absolute;
            top: 50%;
            left: 50%;
            transform: translate(-50%, -50%);
            background: #00b3ff;
            color: white;
            border: none;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
            border-radius: 50%;
            width: 45px;
            height: 45px;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.2rem;
            z-index: 2147483647;
            cursor: pointer;
            transition: opacity 0.3s ease, transform 0.2s ease;
        }

        .status-overlay-btn:active {
            transform: translate(-50%, -50%) scale(0.95);
            background: #009ce0;
        }

        .click-layer {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 85%;
            z-index: 20;
            background: transparent;
            cursor: pointer;
        }

        .custom-fs-btn {
            position: absolute;
            bottom: 35px;
            right: 25px;
            width: 35px;
            height: 35px;
            font-size: 0.8rem;
            background: rgba(255, 255, 255, 0.1);
            backdrop-filter: blur(15px);
            -webkit-backdrop-filter: blur(15px);
            border: 1px solid rgba(255, 255, 255, 0.3);
            box-shadow: 0 4px 15px rgba(0, 0, 0, 0.2);
            color: white;
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            cursor: pointer;
            z-index: 2147483647;
            transition: opacity 0.3s ease;
            opacity: 1;
            pointer-events: auto;
        }

        .custom-fs-btn:active {
            transform: scale(0.95);
            background: rgba(255, 255, 255, 0.2);
        }

        .plyr--hide-controls .seek-overlay-btn,
        .plyr--hide-controls .status-overlay-btn,
        .plyr--hide-controls .custom-fs-btn {
            opacity: 0 !important;
            pointer-events: none !important;
            cursor: default;
        }

        .plyr--paused .seek-overlay-btn,
        .plyr--paused .status-overlay-btn,
        .plyr--paused .custom-fs-btn {
            opacity: 1 !important;
            pointer-events: auto !important;
        }

        .plyr__control--overlaid {
            display: none !important;
            opacity: 0 !important;
            visibility: hidden !important;
        }

        .plyr__controls {
            z-index: 100 !important;
            position: absolute;
            bottom: 0;
            width: 100%;
        }

        .yt-full-shield {
            position: absolute;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            z-index: 50;
            background: transparent;
            cursor: pointer;
        }

        .plyr__video-embed iframe {
            transform: scale(1.01);
        }

        .video-toast {
            position: absolute;
            top: 40px;
            left: 50%;
            transform: translateX(-50%);
            background: rgba(0, 0, 0, 0.8);
            color: white;
            padding: 10px 20px;
            border-radius: 30px;
            font-size: 0.9rem;
            pointer-events: none;
            opacity: 0;
            transition: opacity 0.3s;
            z-index: 2147483647;
            white-space: nowrap;
            font-weight: 600;
            box-shadow: 0 2px 10px rgba(0, 0, 0, 0.3);
            border: 1px solid rgba(255, 255, 255, 0.2);
        }

        .video-toast.visible {
            opacity: 1;
        }

        .fake-fullscreen {
            position: fixed !important;
            top: 0 !important;
            left: 0 !important;
            width: 100% !important;
            height: 100% !important;
            z-index: 2147483647 !important;
            background: #000 !important;
            margin: 0 !important;
            border-radius: 0 !important;
        }

        .fake-fullscreen .custom-fs-btn {
            bottom: 50px;
            right: 50px;
        }

        .plyr {
            position: relative;
            width: 100%;
            height: 100%;
        }

        /* LAYOUT */
        /* Đã thêm border-radius để bo tròn 2 góc dưới */
        .hero {
            background: linear-gradient(135deg, #004e9a 0%, #002855 100%);
            color: white;
            padding: 60px 20px;
            text-align: center;
            margin-bottom: 40px;
            border-radius: 0 0 50px 50px;
            /* Hoặc 30px tùy ý bạn muốn bo nhiều hay ít */
        }

        .hero h1 {
            margin: 0;
            font-size: 2.2rem;
            font-weight: 800;
        }

        .container {
            max-width: 1200px;
            margin: 0 auto;
            padding: 0 20px;
            margin-bottom: 30px;
            flex: 1;
        }

        .grid {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
            gap: 30px;
        }

        .card {
            background: white;
            border-radius: 15px;
            overflow: hidden;
            box-shadow: 0 5px 20px rgba(0, 0, 0, 0.05);
            transition: 0.3s;
            cursor: pointer;
            display: flex;
            flex-direction: column;
            border: 1px solid #eee;
            position: relative;
        }

        .card:hover {
            transform: translateY(-8px);
            box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
            border-color: var(--primary);
        }

        .card-img {
            height: 180px;
            background: #eee;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 3rem;
            color: rgba(255, 255, 255, 0.8);
            position: relative;
            overflow: hidden;
        }

        .card-img img {
            width: 100%;
            height: 100%;
            object-fit: cover;
            transition: 0.5s;
        }

        .card:hover .card-img img {
            transform: scale(1.1);
        }

        .card-body {
            padding: 20px;
            flex-grow: 1;
            display: flex;
            flex-direction: column;
        }

        .card-title {
            font-weight: 700;
            font-size: 1.15rem;
            margin-bottom: 8px;
            color: #333;
        }

        .card-desc {
            font-size: 0.9rem;
            color: #666;
            margin-bottom: 15px;
            display: -webkit-box;
            -webkit-line-clamp: 2;
            line-clamp: 2;
            -webkit-box-orient: vertical;
            overflow: hidden;
        }

        .card-footer {
            margin-top: auto;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding-top: 15px;
            border-top: 1px solid #f0f0f0;
        }

        .price-current {
            font-weight: 800;
            color: var(--accent);
            font-size: 1.1rem;
        }

        .price-old {
            text-decoration: line-through;
            color: #999;
            font-size: 0.85rem;
        }

        .vip-text {
            font-weight: 800;
            color: #f1c40f;
            font-size: 1.1rem;
            text-shadow: 0 1px 1px rgba(0, 0, 0, 0.1);
        }

        .status-badge {
            padding: 5px 12px;
            border-radius: 20px;
            font-size: 0.8rem;
            font-weight: 700;
        }

        .status-owned {
            background: #e6ffea;
            color: #2ecc71;
            border: 1px solid #2ecc71;
        }

        .status-locked {
            background: #fff0f0;
            color: #e74c3c;
            border: 1px solid #e74c3c;
        }

        .vip-tag {
            position: absolute;
            top: 10px;
            right: 10px;
            background: #f1c40f;
            color: #333;
            padding: 5px 12px;
            border-radius: 20px;
            font-weight: 800;
            font-size: 0.8rem;
            box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
            z-index: 10;
        }

        .btn-intro-static {
            display: inline-flex;
            align-items: center;
            gap: 10px;
            background: #e0e0e0;
            color: #555;
            padding: 10px 25px;
            border-radius: 50px;
            font-weight: 700;
            font-size: 0.9rem;
            margin-bottom: 30px;
            transition: 0.3s;
        }

        .btn-intro-static:hover {
            background: var(--primary);
            color: white;
            transform: translateX(5px);
        }

        /* MODAL */
        .modal {
            display: none;
            position: fixed;
            top: 0;
            left: 0;
            width: 100%;
            height: 100%;
            background: rgba(0, 0, 0, 0.95);
            z-index: 2000;
            overflow: hidden;
        }

        .modal.active {
            display: flex;
            flex-direction: column;
        }

        .modal-header {
            height: 60px;
            background: #1a1a1a;
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 0 30px;
            color: white;
            border-bottom: 1px solid #333;
        }

        .modal-body {
            display: flex;
            flex: 1;
            height: calc(100dvh - 60px);
            overflow: hidden;
        }

        .player-left {
            flex: 1;
            min-width: 0;
            background: #000;
            position: relative;
        }

        iframe {
            width: 100%;
            height: 100%;
            border: none;
        }

        .player-right {
            width: 350px;
            flex: none;
            background: #fff;
            border-left: 1px solid #ddd;
            display: flex;
            flex-direction: column;
        }

        .curriculum-list {
            overflow-y: auto;
            flex: 1;
            padding-bottom: 20px;
        }

        .module-title {
            background: #004e9a;
            color: white;
            padding: 15px 20px;
            font-weight: 800;
            font-size: 1rem;
            text-transform: uppercase;
            border-bottom: 1px solid rgba(255, 255, 255, 0.1);
            cursor: pointer;
            display: flex;
            justify-content: space-between;
            align-items: center;
            user-select: none;
        }

        .chapter-title {
            background: #f1f3f5;
            padding: 12px 20px;
            font-weight: 700;
            font-size: 0.95rem;
            color: #333;
            border-bottom: 1px solid #e9ecef;
            display: flex;
            align-items: center;
            cursor: pointer;
            user-select: none;
        }

        .chapter-title i {
            color: #004e9a;
            margin-right: 8px;
        }

        .lesson-header {
            padding: 10px 20px 10px 35px;
            background: white;
            border-bottom: 1px solid #f8f9fa;
            cursor: pointer;
            font-weight: 600;
            font-size: 0.9rem;
            color: #444;
            display: flex;
            justify-content: space-between;
            align-items: center;
            transition: 0.2s;
        }

        .lesson-header:hover {
            background: #f8f9fa;
            color: var(--primary);
        }

        .lesson-header i.icon-prefix {
            margin-right: 8px;
            color: #666;
            font-size: 0.8rem;
        }

        .lesson-sub-item {
            padding: 8px 20px 8px 50px;
            border-bottom: 1px solid #f1f1f1;
            cursor: pointer;
            font-size: 0.85rem;
            color: #555;
            display: flex;
            align-items: center;
            justify-content: space-between;
            transition: 0.2s;
            background: #fdfeff;
        }

        .lesson-sub-item:hover {
            background: #eef4ff;
            color: var(--primary);
        }

        .lesson-sub-item i {
            margin-right: 8px;
            width: 15px;
            text-align: center;
        }

        .lesson-sub-item.active-video {
            background-color: #d6eaff;
            color: #004e9a;
            font-weight: 700;
            border-left: 4px solid #004e9a;
            padding-left: 46px;
        }

        .lesson-sub-item.active-video i {
            color: #004e9a;
            transform: scale(1.2);
        }

        .doc-sub-item {
            font-style: italic;
            color: #666;
        }

        .doc-sub-item:hover {
            color: #856404;
            background: #fffcf5;
        }

        .toggle-icon {
            margin-left: auto;
            transition: transform 0.3s;
            font-size: 0.8rem;
            color: #999;
        }

        .toggle-content {
            display: block;
            overflow: hidden;
            transition: all 0.3s ease;
        }

        .collapsed-header .toggle-icon {
            transform: rotate(-90deg);
        }

        

        /* --- MEDIA QUERY CHO IPAD PRO, IPAD MINI & TABLET --- */
        

        /* --- MEDIA QUERY CHO ĐIỆN THOẠI NHỎ (IPHONE SE, MÀN <= 380px) --- */
        @media (max-width: 380px) {
            .nav-links {
                gap: 10px;
            }

            /* Thu hẹp khoảng cách giữa các nút */
            .nav-links a {
                font-size: 0.85rem;
            }

            /* Giảm nhẹ font chữ để đảm bảo vừa đúng 2 hàng */
        }

        /* --- MEDIA QUERY CHO ĐIỆN THOẠI (DỌC) - FIX LỖI MODAL BÀI HỌC --- */
        /* --- MEDIA QUERY CHO ĐIỆN THOẠI (DỌC) - FIX LỖI MODAL BÀI HỌC --- */
        @media (max-width: 768px) {
            .modal-body {
                flex-direction: column;
            }

            .player-left {
                width: 100%;
                flex: none;
                height: 35vh;
                min-height: 250px;
            }

            .player-right {
                width: 100%;
                flex: 1;
                min-height: 0;
                /* <-- Thuộc tính cốt lõi để fix lỗi scroll */
                border-left: none;
                border-top: 1px solid #ddd;
            }
        }