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

        /* [UPDATED] CSS Chặn hành vi zoom, copy & kéo nảy trên Mobile */
        html,
        body {
            /* Chống bôi đen text */
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
            /* Chặn zoom bằng cử chỉ chạm */
            touch-action: pan-x pan-y;
            /* Chặn hiệu ứng kéo nảy */
            overscroll-behavior: none;
        }

        body {
            font-family: 'Montserrat', sans-serif;
            background: var(--bg);
            color: var(--text);
            margin: 0;
            min-height: 100vh;
            display: flex;
            flex-direction: column;
        }

        .navbar,
        .page-header,
        .container {
            width: 100%;
            box-sizing: border-box;
        }

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

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

        .page-header {
            background: linear-gradient(135deg, var(--primary), #002d5b);
            color: white;
            padding: 40px 20px 80px;
            text-align: center;
            border-radius: 0 0 30px 30px;
            margin-bottom: 40px;
        }

        .page-header h1 {
            margin: 0;
            font-size: 2rem;
        }

        .breadcrumb {
            margin-top: 10px;
            opacity: 0.8;
            font-size: 0.9rem;
        }

        .search-wrapper {
            margin: -65px auto 40px;
            width: 90%;
            max-width: 700px;
            position: relative;
            z-index: 10;
        }

        .search-bar {
            background: white;
            display: flex;
            align-items: center;
            padding: 5px;
            border-radius: 60px;
            box-shadow: 0 15px 35px rgba(0, 0, 0, 0.15);
            overflow: hidden;
            box-sizing: border-box;
        }

        .search-bar input {
            flex: 1;
            border: none;
            padding: 15px 25px;
            border-radius: 50px;
            outline: none;
            font-size: 1.1rem;
            width: 0;
            box-sizing: border-box;
        }

        .search-bar button {
            background: var(--primary);
            color: white;
            border: none;
            padding: 12px 30px;
            border-radius: 50px;
            font-weight: 800;
            cursor: pointer;
            transition: 0.3s;
            flex-shrink: 0;
            white-space: nowrap;
        }

        .search-bar button:hover {
            background: #003366;
            transform: scale(1.05);
        }

        .container {
            max-width: 1240px;
            margin: 0 auto;
            padding: 20px;
            flex: 1;
        }

        .grid-subjects {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
            gap: 25px;
        }

        .subject-card {
            background: var(--white);
            border-radius: 15px;
            box-shadow: var(--shadow);
            transition: 0.3s;
            display: flex;
            flex-direction: column;
            border: 1px solid #eee;
            overflow: hidden;
            position: relative;
        }

        .subject-card:hover {
            transform: translateY(-7px);
            box-shadow: 0 15px 30px rgba(0, 0, 0, 0.1);
            border-color: var(--primary);
        }

        .card-top-accent {
            height: 6px;
            background: linear-gradient(to right, #004e9a, #00c6ff);
        }

        .card-body {
            padding: 25px;
            flex-grow: 1;
        }

        .subject-icon {
            width: 55px;
            height: 55px;
            background: #f0f7ff;
            color: var(--primary);
            border-radius: 50%;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.8rem;
            margin-bottom: 15px;
            transition: 0.3s;
        }

        .subject-card:hover .subject-icon {
            background: var(--primary);
            color: white;
        }

        .subject-name {
            font-size: 1.2rem;
            font-weight: 700;
            display: block;
            margin-bottom: 8px;
            color: #333;
        }

        .subject-info {
            font-size: 0.9rem;
            color: #777;
        }

        .card-footer {
            padding: 15px 25px;
            background: #fcfcfc;
            border-top: 1px solid #f0f0f0;
            text-align: right;
        }

        .btn-go {
            background: white;
            color: var(--primary);
            font-weight: 700;
            font-size: 0.85rem;
            padding: 8px 20px;
            border-radius: 20px;
            border: 2px solid var(--primary);
            display: inline-block;
        }

        .subject-card:hover .btn-go {
            background: var(--primary);
            color: white;
        }

        

        

        /* --- 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 */
        }