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

body {
    font-family: Arial, sans-serif;
    background-color: #f5f5f5;
}

.container {
    display: flex;
    height: 100vh;
    width: 100%;
}

.left-frame {
    width: 250px;
    background-color: #333;
    color: white;
    padding: 20px;
    overflow-y: auto;
}

.central-frame {
    flex-grow: 1;
    height: 100%;
}

#central-frame {
    width: 100%;
    height: 100%;
    border: none;
}

.nav-menu {
    list-style-type: none;
    margin-top: 20px;
}

.nav-menu li {
    margin-bottom: 10px;
}

.nav-menu a {
    color: white;
    text-decoration: none;
    display: block;
    padding: 8px 10px;
    border-radius: 4px;
    transition: background-color 0.3s;
}

.nav-menu a:hover {
    background-color: #555;
}

h2 {
    border-bottom: 1px solid #555;
    padding-bottom: 10px;
    margin-bottom: 15px;
}

@media (max-width: 768px) {
    .container {
        flex-direction: column;
    }
    
    .left-frame {
        width: 100%;
        height: auto;
        max-height: 30vh;
    }
    
    .central-frame {
        height: 70vh;
    }
}