.header {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    padding: 0 40px;
    background-color: #ffffff;
    z-index: 1000;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    height: 80px; /* Fixed height for consistency */
    transition: top 0.3s ease;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-sizing: border-box;
}

.header.with-demo-warning {
    top: 45px;
}

.logo-container {
    display: flex;
    align-items: center;
}

.logo-container img {
    width: 200px;
    height: auto;
}

.options-container {
    display: flex;
    align-items: center;
    gap: 30px;
}

.header .options-container a {
    color: #0e2050;
    text-decoration: none;
    position: relative;
    display: inline-block;
    font-weight: 500;
    font-size: 18px;
    transition: color 0.3s ease;
}

.header .options-container a::before {
    content: '';
    position: absolute;
    left: 0;
    bottom: -4px;
    width: 100%;
    height: 2px;
    background-color: #ffd700;
    transform: scaleX(0);
    transition: transform 0.3s ease;
}

.header .options-container a:hover {
    color: #0e2050; /* Keep color consistent */
}

.header .options-container a:hover::before {
    transform: scaleX(1);
}

.demo-warning {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    background-color: #fff3cd;
    color: #856404;
    border-bottom: 1px solid #ffeeba;
    padding: 0 16px;
    font-family: system-ui, sans-serif;
    font-size: 14px;
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 9999;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    height: 45px;
    box-sizing: border-box;
}

.demo-warning strong {
    font-weight: bold;
}

.demo-warning a {
    color: #856404;
    text-decoration: underline;
    margin: 0 3px;
}

.demo-warning code {
    background-color: #f8f9fa;
    padding: 2px 4px;
    border-radius: 3px;
    font-family: 'Courier New', monospace;
    font-size: 13px;
}

/* --- Responsive Design --- */

@media (max-width: 900px) {
    .header {
        padding: 0 20px;
        height: 60px;
    }
    
    .logo-container img {
        width: 150px;
    }

    .options-container {
        gap: 15px;
    }
}

@media (max-width: 600px) {
    .header {
        flex-direction: column;
        height: auto;
        padding: 10px;
    }

    .logo-container {
        margin-bottom: 10px;
    }
    
    .logo-container img {
        width: 120px;
    }

    .options-container {
        flex-wrap: wrap;
        justify-content: center;
        gap: 15px;
    }
}