<style>
    {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
    }
 
    body {
        font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
        padding-top: 80px;
        background: linear-gradient(90deg, yellow, orange 80%);
    }

    /* Navigation Styles */
    .navbar {
        background: linear-gradient(135deg, #555555 0%, #232323 100%);
        color: white;
        padding: 0;
        position: fixed;
        top: 0;
        left: 0;
        right: 0;
        z-index: 999;
        height: 80px;
        box-shadow: 0 2px 10px rgba(0,0,0,0.1);
        justify-content: space-between;
        text-align: center;
    }

    .nav-container {
        display: flex;
        justify-content: space-between;
        align-items: center;
        max-width: 90%;
        margin: 0 auto;
        column-gap: 10px;
    }

    .navMenu {
        display: flex;
        justify-content: space-between;
        align-items: center;
        width: 90%;
        margin: 0 auto;
        column-gap: 5px;
    }

    .nav-item {
        align-items: center;
        justify-content: center;
        column-gap: 5px;
    }

    .nav-logo {
        display: flex;
        margin-top: 0;
        height: 70px;
        width: auto;
    }

    .nav-logo2 {
        display: flex;
        margin-top: 0;
        height: 70px;
        width: auto;
    }



    /* Mobile Menu */
     /* Hamburger Menu */
    .hamburger {
        display: flex;
        flex-direction: column;
        cursor: pointer;
        padding: 5px;
        transition: transform 0.3s ease;
        margin-right: 20px;
    }

    .hamburger:hover {
        transform: scale(1.1);
    }

    .hamburger span {
        width: 25px;
        height: 3px;
        background-color: white;
        margin: 3px 0;
        transition: 0.3s;
        border-radius: 2px;
        
    }

    .hamburger.active span:nth-child(1) {
        transform: rotate(-45deg) translate(-5px, 6px);
    }

    .hamburger.active span:nth-child(2) {
        opacity: 0;
    }

    .hamburger.active span:nth-child(3) {
        transform: rotate(45deg) translate(-5px, -6px);
    }

    .nav-menu {
        position: fixed;
        top: 80px;
        left: -100%;
        width: 100%;
        height: calc(100vh - 70px);
        background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
        transition: left 0.3s ease;
        overflow-y: auto;
        padding: 1rem 0;
        justify-content: center;
        text-align: center;
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-logo {
        display: flex;
        height: auto;
        width: 180px;
    }

    .nav-logo2 {
        display: flex;
        margin-top: 0;
        height: auto;
        width: 80px;
    }

        .nav-item {
            list-style: none;
            border-bottom: 1px solid rgba(255,255,255,0.1);
        }

        .nav-link {
            display: flex;
            justify-content: space-between;
            align-items: center;
            padding: 1rem 1.5rem;
            color: white;
            text-decoration: none;
            font-size: 16pt;
            transition: background-color 0.3s ease;
        }

        .nav-link:hover {
            background-color: rgba(255,255,255,0.1);
        }

        /* Dropdown Arrow */
        .dropdown-arrow {
            transition: transform 0.3s ease;
            font-size: 0.8rem;
        }

        .dropdown-arrow.active {
            transform: rotate(180deg);
        }

        /* Dropdown Menu */
        .dropdown {
            max-height: 0;
            overflow: hidden;
            transition: max-height 0.3s ease;
            background-color: rgba(0,0,0,0.1);
        }

        .dropdown.active {
            max-height: 500px;
            }

        .parent-dropdown {
            height: max-content;
        }

        .dropdown-item {
            padding: 0.8rem 2.5rem;
            color: rgba(255,255,255,0.9);
            text-decoration: none;
            display: block;
            font-size: 0.95rem;
            transition: background-color 0.3s ease;
            border-bottom: 1px solid rgba(255,255,255,0.05);
        }

        .dropdown-item:hover {
            background-color: rgba(255,255,255,0.1);
            color: white;           
        }

        .dropdown-item:last-child {
            border-bottom: none;
        }

        .icon-admin {
            height: 50px;
            width: 50px;
        }
        /* วิทีอาร์โรงเรียน + ปฏิทินวิชาการ */
        .vtrcalendar {
            display: flex;
            width: auto;
            height: 200px;
            margin-top: 10px;
            margin-bottom: 10px;
            align-items: center;
            justify-content: center;
            gap: 5px;
            background: linear-gradient(135deg, yellow, orange 100%);
        }

            .video{
            display: flex;
            width: 90%;
            height: 20%;
            border-radius: 10px;
            align-content: center;
            align-items: center;
            justify-content: center;
            text-align: center;

            }
            .present-container {
            display: flex;
            width: 50%;
            height: 90%;
            align-content: center;
            align-items: center;
            justify-content: center;
            text-align: center;
            }

            .calendarcontainer {
                display: flex;
                flex-direction: column;
                width: 50%;
                height: 60%;
                align-content: center;
                justify-content: center;
                align-items: center;
                
            }

            .textcontainercalendar {
                display: flex;
                background: linear-gradient(135deg, #555555 0%, #232323 100%);
                margin-top: 5px;
                padding: 10px;
                width: 90%;
                border-radius: 10px;
                align-content: center;
                justify-content: center;
                text-align: center;
                align-items: center;
            }

            .textcalendar {
                display: flex;
                width: 100%;
                height: auto;
                align-content: center;
                justify-content: center;
                text-align: center;
                color: #f0f0f0;
                font-size: large;
                font-family: 'Sarabun', sans-serif;   
            }

            .vckcalendar {
                display: flex;
                width: 100%;
                height: 100%;
                
                
            }

        /* Content Area */
        .content {
            padding: 2rem;
            max-width: 1200px;
            margin: 0 auto;
        }

        .content h1 {
            color: #333;
            margin-bottom: 1rem;
        }

        .content p {
            line-height: 1.6;
            color: #666;
        }

        /* Desktop Styles */
        @media (min-width: 768px) {
            .hamburger {
                display: none;
            }

            .nav-container {
                display: flex;
                height: 80px;
                max-width: 100%;
                justify-content: center;
                text-align: center;
            }

            .nav-menu {
                position: static;
                display: flex;
                width: 100%;
                height: 60px;
                background: none;
                padding: 0;
                margin-top: 15px;
                overflow: visible;
                justify-content: center;
                text-align: center;
            }

            .nav-logo {
                position: flex;
                height: auto;
                width: 200px;
            }

            .nav-item {
                position: relative;
                border-bottom: none;
                margin-top: 10px;
            }

            .nav-link {
                font-family: sans-serif;
                padding: 0.5rem 1rem;
                font-size: 13pt;
            }

            .nav-link:hover {
            background-color: rgba(255,255,255,0.1);
            border-radius: 10px; 
            }

            .dropdown {
                position: absolute;
                top: 100%;
                left: 0;
                width: 300px;
                background: white;
                box-shadow: 0 4px 6px rgba(0,0,0,0.1);
                border-radius: 5px;
                margin-top: 0.5rem;
                max-height: 0;
            }

            .dropdown.active {
                max-height: 1000px;
            }

            .parent-dropdown {
                height: max-content;
            }


            .dropdown-item {
                top: 100px;
                min-width: none;
                color: #333;
                padding: 0.8rem 1rem;
            }

            .dropdown-item:hover {
                background-color: #f0f0f0;
                color: #667eea;
            }

            .icon-admin {
                display: flex;
                height: 50px;
                width: 50px;
                justify-content: center;
                align-items: center;
                transition: transform 0.3s ease;
            }

            .icon-admin:hover {
                transform: rotate(45deg);
            }
/* 
            .admin-link:hover .text-for-admin {
                display: block;
            } */

            /* วิทีอาร์โรงเรียน + ปฏิทินวิชาการ */
            .vtrcalendar {
                display: flex;
                width: 100%;
                height: 400px;
                margin-top: 10px;
                align-items: center;
                justify-content: center;
                gap: 20px;
                background: linear-gradient(135deg, yellow, orange 100%);
            }

            .video{
            display: flex;
            width: 90%;
            height: 90%;
            border-radius: 10px;
            margin-top: 20px;

            }
            .present-container {
            display: flex;
            width: 30%;
            height: 80%;
            /* border: 2px solid red; */
            align-content: center;
            align-items: center;
            justify-content: center;
            text-align: center;
            }

            .calendarcontainer {
                display: flex;
                flex-direction: column;
                justify-content: space-around;
                width: 30%;
                height: auto;
                align-content: center;
                justify-content: center;
                align-items: center;
                
            }

            .textcontainercalendar {
                display: flex;
                background: linear-gradient(135deg, #555555 0%, #232323 100%);
                margin-top: 0px;
                padding-bottom: 3px;
                width: 60%;
                border-radius: 10px;
                align-content: center;
                justify-content: center;
                text-align: center;
                align-items: center;
            }

            .textcalendar {
                display: flex;
                width: 60%;
                height: auto;
                align-content: center;
                justify-content: center;
                text-align: center;
                color: #f0f0f0;
                font-size: large;
                font-family: 'Sarabun', sans-serif;   
            }

            .vckcalendar {
                display: flex;
                width: 80%;
                height: 300px;
                
            }

           .newsletters {
                margin-left: 30px;
                margin-right: 30px;
           }


        }
</style>