/* General styling */
body {
    margin: 0;
    padding: 0;
    font-family: Arial, sans-serif;
    background: #f9fafb; /* subtle professional background */
    color: #333;
}

header {
    width: 100%;
    text-align: center;
    padding: 20px 0;
    background: #2c3e50; /* professional dark blue */
    color: #ffffff;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

nav a {
    margin: 0 10px;
    text-decoration: none;
    color: #ecf0f1; /* light color for contrast */
    font-weight: bold;
}

    nav a:hover {
        color: #1abc9c; /* subtle hover color */
    }

main {
    max-width: 700px;
    width: 90%;
    background: #ffffff;
    margin: 20px auto;
    padding: 20px;
    border-radius: 10px;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
    display: flex;
    flex-direction: column;
    align-items: center;
}

h1, h2, h3 {
    text-align: center;
}

h2 {
    color: #34495e; /* slightly darker headings */
}

.intro {
    margin-bottom: 20px;
}

.upload-section {
    text-align: center;
    margin: 20px 0;
}

.upload-label {
    display: block;
    margin-bottom: 10px;
    font-size: 1.2em;
    font-weight: bold;
    color: #2c3e50;
}

input[type="file"] {
    padding: 10px;
    border: 1px solid #bdc3c7;
    border-radius: 5px;
}

.info-section {
    margin-top: 30px;
}

footer {
    margin: 30px 0;
    text-align: center;
    color: #777;
}

/* Ad containers */
.ad-container {
    width: 100%;
    display: flex;
    justify-content: center;
    margin: 20px 0;
}

.ad-placeholder {
    width: 100%;
    max-width: 600px;
    height: 100px;
    background: #ecf0f1; /* light professional gray */
    border: 1px dashed #bdc3c7;
    display: flex;
    justify-content: center;
    align-items: center;
    color: #555;
    font-size: 1.1em;
}

/* Responsive design */
@media (max-width: 600px) {
    main {
        padding: 15px;
    }

    .ad-placeholder {
        height: 80px;
    }

    nav a {
        display: inline-block;
        margin: 5px;
    }
}