header {
    background-color: #66b3ff; 
    text-align: center;
    color: white;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    z-index: 1000;
    font-size: 18px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.2);
    box-sizing: border-box;
}


.sidebar {
    height: 100%;
    width: 0; 
    position: fixed;
    z-index: 1100;
    top: 0;
    left: 0;
    background-color: #3b8f99; 
    overflow-x: hidden;
    transition: 0.5s ease;
    padding-top: 50px;
}


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

.sidebar ul li a {
    padding: 8px 16px; 
    text-decoration: none;
    font-size: 16px; 
    color: #f0f0f0; 
    display: block;
    transition: 0.3s;
}


.sidebar ul li a:hover {
    color: white;
    background-color: #66b3ff; 
}


.open-btn {
    font-size: 18px;
    cursor: pointer;
    background-color: #2c6d7f; 
    color: white;
    padding: 8px;
    border: none;
    position: fixed;
    top: 15px;
    left: 15px;
    z-index: 1200;
}


.content {
    padding: 20px;
    margin-top: 50px;
    transition: margin-left 0.5s ease;
}


.close-btn {
    font-size: 22px; 
    color: white;
    background: none;
    border: none;
    cursor: pointer;
    position: absolute;
    top: 10px;
    right: 15px;
}


@media screen and (max-width: 768px) {
    .sidebar {
        width: 100%;
    }
    .open-btn {
        font-size: 16px; 
        left: 10px;
    }
    .content {
        margin-left: 0;
    }
}