:root {
    --bg-color: #ffffff;
    --text-color: #000000;
    --text-secondary: #555555;
    --accent-color: #0047AB;
    /* Cobalt Blue */
    --accent-hover: #003380;
    --border-color: #e5e5e5;
    --font-main: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    --spacing-section: 120px;
    --spacing-element: 2rem;
    --container-width: 1200px;
    --transition: 0.3s cubic-bezier(0.25, 0.46, 0.45, 0.94);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    scroll-behavior: smooth;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    font-family: var(--font-main);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* Typography */
h1,
h2,
h3,
h4,
h5,
h6 {
    font-weight: 600;
    line-height: 1.1;
    letter-spacing: -0.02em;
}

h1 {
    font-size: 4.5rem;
    margin-bottom: 1.5rem;
}

h2 {
    font-size: 3rem;
    margin-bottom: 1rem;
}

h3 {
    font-size: 1.5rem;
    margin-bottom: 0.5rem;
}

p {
    font-size: 1.125rem;
    color: var(--text-secondary);
    margin-bottom: 1.5rem;
    max-width: 65ch;
}

a {
    text-decoration: none;
    color: inherit;
    transition: var(--transition);
}

/* Utilities */
.container {
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 2rem;
}

.section {
    padding: var(--spacing-section) 0;
}

.text-center {
    text-align: center;
}

.text-accent {
    color: var(--accent-color);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 1rem 2rem;
    font-weight: 500;
    border-radius: 4px;
    /* Minimal radius */
    cursor: pointer;
    transition: var(--transition);
    font-size: 1rem;
}

.btn-primary {
    background-color: var(--text-color);
    color: var(--bg-color);
    border: 1px solid var(--text-color);
}

.btn-primary:hover {
    background-color: var(--accent-color);
    border-color: var(--accent-color);
    color: #fff;
}

.btn-link {
    padding: 0;
    color: var(--accent-color);
    font-weight: 600;
}

.btn-link:hover {
    color: var(--text-color);
}

/* Navbar */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: transparent;
    z-index: 1000;
    padding: 1.2rem 0;
    transition: background 0.3s ease, padding 0.3s ease, border-color 0.3s ease;
}

.navbar.scrolled {
    background: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    /* Slightly smaller padding on scroll */
}

.navbar .container {
    display: flex;
    align-items: center;
    position: relative;
    height: 40px;
    /* Fixed height for alignment */
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    /* Removed negative letter-spacing for more natural look */
    display: flex;
    align-items: center;
    gap: 0.75rem;
    color: var(--text-color);
    z-index: 2;
}

.logo-icon {
    height: 32px;
    width: auto;
    display: block;
}

.nav-links {
    display: flex;
    gap: 2rem;
    list-style: none;
    margin-left: auto;
    /* Pushes links to the right */
    padding: 0;
}

.nav-links a {
    font-size: 0.95rem;
    /* Standard size */
    font-weight: 500;
    /* Slightly lighter than 600 for natural look */
    color: var(--text-color);
    transition: color 0.2s ease;
}

.nav-links a:hover {
    color: var(--accent-color);
}

/* Auth Buttons */
.nav-auth {
    display: flex;
    align-items: center;
    gap: 1.5rem;
    margin-left: 2.5rem;
    /* Removed padding and border */
    height: 30px;
    /* Match height for alignment */
}

.nav-login {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-color);
}

.nav-login:hover {
    color: var(--accent-color);
}

.btn-sm {
    padding: 0.5rem 1.25rem;
    font-size: 0.9rem;
    border-radius: 6px;
}

/* Hero Section */
.hero {
    padding-top: 200px;
    padding-bottom: 150px;
    min-height: 90vh;
    display: flex;
    align-items: center;
    position: relative;
    overflow: hidden;
}

.hero-video {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    z-index: 0;
}

.hero::after {
    content: '';
    position: absolute;
    inset: 0;
    background: rgba(255, 255, 255, 0.85);
    /* White overlay */
    z-index: 1;
}

.hero-content {
    max-width: 800px;
    position: relative;
    z-index: 2;
}

.hero-subtitle {
    font-size: 1.5rem;
    color: var(--text-color);
    font-weight: 400;
    margin-bottom: 2rem;
    display: block;
}

.hero-description {
    font-size: 1.25rem;
    color: var(--text-secondary);
    margin-bottom: 3rem;
}

/* What is RoboBridge */
.about-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: start;
}

.about-list {
    list-style: none;
    margin-top: 2rem;
}

.about-list li {
    padding: 1rem 0;
    border-bottom: 1px solid var(--border-color);
    font-size: 1.1rem;
    display: flex;
    align-items: center;
}

.about-list li::before {
    content: '→';
    margin-right: 1rem;
    color: var(--accent-color);
}

/* Core Content Areas */
.content-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 2rem;
}

.content-card {
    background: #f9f9f9;
    padding: 3rem;
    transition: var(--transition);
    border: 1px solid transparent;
}

.content-card:hover {
    background: #fff;
    border-color: var(--border-color);
    box-shadow: 0 20px 40px rgba(0, 0, 0, 0.05);
    transform: translateY(-5px);
}

.card-number {
    font-size: 0.9rem;
    color: var(--accent-color);
    font-weight: 600;
    margin-bottom: 1rem;
    display: block;
}

/* Featured Articles */
.articles-list {
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

.article-item {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 2rem;
    padding: 2rem 0;
    border-bottom: 1px solid var(--border-color);
    align-items: center;
    transition: var(--transition);
}

.article-item:hover {
    padding-left: 1rem;
    border-bottom-color: var(--accent-color);
}

.article-content h3 {
    font-size: 1.75rem;
    margin-bottom: 0.5rem;
}

.article-meta {
    text-align: right;
    font-size: 0.9rem;
    color: var(--accent-color);
    font-weight: 600;
}

/* Newsletter */
.newsletter {
    background-color: #f5f5f5;
}

.newsletter-form {
    display: flex;
    gap: 1rem;
    max-width: 500px;
    margin-top: 2rem;
}

.newsletter-input {
    flex: 1;
    padding: 1rem;
    border: 1px solid #ddd;
    background: #fff;
    font-family: inherit;
    font-size: 1rem;
}

.newsletter-input:focus {
    outline: none;
    border-color: var(--accent-color);
}

/* Footer */
footer {
    padding: 4rem 0;
    border-top: 1px solid var(--border-color);
    font-size: 0.9rem;
    color: var(--text-secondary);
}

.footer-content {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.footer-content p {
    margin-bottom: 0;
}

/* Responsive */
@media (max-width: 768px) {
    h1 {
        font-size: 3rem;
    }

    h2 {
        font-size: 2.25rem;
    }

    .about-grid,
    .content-grid,
    .article-item {
        grid-template-columns: 1fr;
    }

    .nav-links,
    .nav-auth {
        display: none;
    }

    /* Mobile menu to be implemented */

    .hero {
        padding-top: 150px;
        text-align: center;
    }

    .hero-content {
        margin: 0 auto;
    }

    .article-meta {
        text-align: left;
        margin-top: 0.5rem;
    }
}