/* Facebook-inspired Style Guide */
:root {
    --fb-blue: #1877F2;
    --fb-bg: #F0F2F5;
    --fb-white: #FFFFFF;
    --fb-text-primary: #1C1E21;
    --fb-text-secondary: #65676B;
    --fb-divider: #CED0D4;
    --fb-hover: #E4E6EB;
    --fb-green: #42B72A;
}

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

body {
    background-color: var(--fb-bg);
    color: var(--fb-text-primary);
    line-height: 1.6;
}

header {
    background-color: var(--fb-white);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
    position: sticky;
    top: 0;
    z-index: 1000;
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
    height: 60px;
}

.logo img {
    height: 40px;
    vertical-align: middle;
}

.nav-links {
    display: flex;
    list-style: none;
}

.nav-links li {
    margin-left: 30px;
}

.nav-links a {
    text-decoration: none;
    color: var(--fb-text-secondary);
    font-weight: 600;
    font-size: 15px;
    transition: color 0.2s;
}

.nav-links a:hover, .nav-links a.active {
    color: var(--fb-blue);
}

/* Sections */
section {
    padding: 80px 20px;
    max-width: 1200px;
    margin: 0 auto;
}

.hero {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 100px 20px;
}

.hero-content {
    flex: 1;
}

.hero-content h1 {
    font-size: 48px;
    color: var(--fb-blue);
    margin-bottom: 20px;
}

.hero-content p {
    font-size: 20px;
    color: var(--fb-text-secondary);
    margin-bottom: 30px;
}

.hero-image {
    flex: 1;
    display: flex;
    justify-content: center;
}

.hero-image img {
    max-width: 100%;
    height: auto;
}

/* Card Style */
.card-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 20px;
    margin-top: 40px;
}

.card {
    background: var(--fb-white);
    padding: 30px;
    border-radius: 8px;
    box-shadow: 0 1px 2px rgba(0, 0, 0, 0.2);
    transition: transform 0.2s;
}

.card:hover {
    transform: translateY(-5px);
}

.card h3 {
    margin-bottom: 15px;
    color: var(--fb-blue);
}

.btn {
    display: inline-block;
    padding: 10px 24px;
    background-color: var(--fb-blue);
    color: white;
    text-decoration: none;
    border-radius: 6px;
    font-weight: bold;
    font-size: 16px;
}

.btn:hover {
    background-color: #166FE5;
}

/* Footer */
footer {
    background-color: var(--fb-white);
    padding: 40px 20px;
    border-top: 1px solid var(--fb-divider);
}

.footer-content {
    max-width: 1200px;
    margin: 0 auto;
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
}

.footer-section {
    flex: 1;
    min-width: 250px;
    margin-bottom: 20px;
}

.footer-section h4 {
    margin-bottom: 15px;
    font-size: 14px;
    color: var(--fb-text-secondary);
    text-transform: uppercase;
}

.footer-section p, .footer-section a {
    font-size: 12px;
    color: var(--fb-text-secondary);
    text-decoration: none;
    display: block;
    margin-bottom: 8px;
}

.footer-bottom {
    max-width: 1200px;
    margin: 20px auto 0;
    padding-top: 20px;
    border-top: 1px solid var(--fb-divider);
    font-size: 12px;
    color: var(--fb-text-secondary);
    text-align: center;
}

.footer-links a {
    margin: 0 10px;
}

@media (max-width: 768px) {
    .hero {
        flex-direction: column;
        text-align: center;
    }
    .hero-content h1 {
        font-size: 32px;
    }
    .nav-links {
        display: none; /* Simplification for desktop-first demo */
    }
}