body {
    font-family: Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f0f0f0;
}

header {
    background-color: #333;
    color: #fff;
    padding: 20px;
    text-align: center;
}

header h1 {
    cursor: pointer;
}

nav {
    margin-top: 10px;
}

nav ul {
    list-style-type: none;
    padding: 0;
}

nav ul li {
    display: inline;
    margin-right: 20px;
}

nav ul li a {
    color: #fff;
    text-decoration: none;
    font-size: 1.2em;
}

header input {
    width: 80%;
    padding: 10px;
    margin-top: 10px;
    font-size: 1em;
}

.container {
    max-width: 1000px;
    margin: auto;
    padding: 20px;
    background-color: #fff;
    box-shadow: 0 0 10px rgba(0, 0, 0, 0.1);
}

.category {
    margin-bottom: 40px;
}

.category h2 {
    font-size: 2em;
    margin-bottom: 20px;
}

.video, .article, .demo {
    margin-bottom: 20px;
}

.video h3, .article h3, .demo h3 {
    font-size: 1.5em;
    margin-bottom: 10px;
}

#load-more-videos {
    display: block;
    margin: 20px auto;
    padding: 10px 20px;
    font-size: 1em;
    cursor: pointer;
}

#about p {
    font-size: 1.2em;
}

#about a {
    margin-right: 10px;
}

@media (max-width: 600px) {
    .video iframe, .article iframe, .demo iframe {
        height: 200px;
    }

    header input {
        width: 95%;
    }
}