body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    line-height: 1.6;
    background-color: #f4f4f4;
}

header {
    background-color: #333;
    color: white;
    padding: 20px 10px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap; 
    text-align: center;
}

nav {
    margin-top: 10px;
}

nav a {
    color: white;
    margin: 0 15px;
    text-decoration: none;
}

nav a:hover {
    text-decoration: underline;
}

main {
    padding: 20px;
    background-color: white;
}

.mainDiv {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap; 
    gap: 20px;
}

.mainDiv div {
    flex: 1 1 300px; 
    max-width: 400px;
    margin-top: 20px;
    border-style: groove;
    padding: 10px;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.7);
    background: #fff;
}

footer {
    background-color: #333;
    color: white;
    text-align: center;
    padding: 10px 0;
    position: relative; 
    width: 100%;
}

@media (max-width: 768px) {
    header {
        flex-direction: column;
    }

    nav a {
        display: block;
        margin: 8px 0;
    }

    .mainDiv {
        flex-direction: column;
        align-items: center;
    }

    .mainDiv div {
        width: 90%; 
        max-width: 100%;
    }
}