* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: Arial, sans-serif;
}

body {
    font-size: 16px;
    line-height: 1.6;
}

.sticky-header {
    position: sticky;
    top: 0;
    background-color: #333;
    color: white;
    padding: 10px 0;
    z-index: 1000;
}

.header-container {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 10px;
}

.logo {
    max-width: 100px;
    height: auto;
    margin-right: 15px;
}

.user-info {
    font-size: 0.9em;
    text-align: center;
}

.user-info p {
    margin: 0;
}

.user-info a {
    color: #ffd700;
    text-decoration: none;
}

.user-info a:hover {
    text-decoration: underline;
}

.sticky-header nav ul {
    display: flex;
    justify-content: center;
    list-style: none;
    padding: 10px 0;
}

.sticky-header nav ul li {
    margin: 0 15px;
}

.sticky-header nav ul li a {
    color: white;
    text-decoration: none;
    font-weight: bold;
}

main {
    padding: 20px;
    max-width: 600px;
    margin: 0 auto;
}

h1 {
    font-size: 1.5em;
    margin-bottom: 20px;
}

p {
    margin-bottom: 10px;
}

.error {
    color: red;
}

@media (max-width: 600px) {
    .header-container {
        flex-direction: column;
        align-items: center;
    }

    .logo {
        max-width: 80px;
        margin-bottom: 10px;
    }

    .user-info {
        font-size: 0.8em;
    }

    .sticky-header nav ul {
        flex-direction: column;
        text-align: center;
    }

    .sticky-header nav ul li {
        margin: 10px 0;
    }
}