/* Reset and Base Styles */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --primary-color: #4a9eff;
    --secondary-color: #6bb0ff;
    --accent-color: #ff6b35;
    --text-primary: #e4e4e7;
    --text-secondary: #a1a1aa;
    --text-muted: #71717a;
    --bg-primary: #0a0a0b;
    --bg-secondary: #18181b;
    --bg-tertiary: #27272a;
    --border-color: #3f3f46;
    --code-bg: #1e1e1e;
    --code-color: #d4d4d8;
    --success-color: #4ade80;
    --warning-color: #fbbf24;
    --error-color: #f87171;
    
    --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', 'Courier New', monospace;
    
    --shadow-sm: 0 1px 3px rgba(0, 0, 0, 0.5);
    --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.5);
    --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.6);
    --shadow-xl: 0 20px 40px rgba(0, 0, 0, 0.7);
    
    --border-radius: 8px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

body {
    font-family: var(--font-primary);
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    overflow-x: hidden;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    line-height: 1.2;
    margin-bottom: 1rem;
}

h1 { font-size: 2.5rem; }
h2 { font-size: 2rem; }
h3 { font-size: 1.5rem; }
h4 { font-size: 1.25rem; }

p {
    margin-bottom: 1rem;
    color: var(--text-secondary);
}

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

a:hover {
    color: var(--secondary-color);
    text-decoration: underline;
}

/* Navigation */
.navbar {
    position: fixed;
    top: 0;
    width: 100%;
    background: rgba(10, 10, 11, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    padding: 1rem 0;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo h1 {
    font-size: 1.5rem;
    color: var(--primary-color);
    margin-bottom: 0;
}

.nav-logo span {
    font-size: 0.875rem;
    color: var(--text-muted);
    display: block;
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-menu a {
    font-weight: 500;
    color: var(--text-primary);
    transition: var(--transition);
}

.nav-menu a:hover {
    color: var(--primary-color);
    text-decoration: none;
}

.hamburger {
    display: none;
    flex-direction: column;
    cursor: pointer;
}

.hamburger span {
    width: 25px;
    height: 3px;
    background: var(--text-primary);
    margin: 3px 0;
    transition: var(--transition);
}

/* Hero Section */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    padding: 6rem 2rem 2rem;
    background: linear-gradient(135deg, var(--bg-primary) 0%, var(--bg-secondary) 100%);
}

.hero-content {
    max-width: 1200px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 4rem;
    align-items: center;
}

.hero h1 {
    font-size: 3.5rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 1rem;
    line-height: 1.1;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--primary-color);
    font-weight: 500;
    margin-bottom: 1.5rem;
}

.hero-description {
    font-size: 1.125rem;
    margin-bottom: 2rem;
    color: var(--text-secondary);
}

.hero-stats {
    display: flex;
    gap: 3rem;
    margin-bottom: 3rem;
}

.stat {
    text-align: center;
}

.stat-number {
    display: block;
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary-color);
    font-family: var(--font-mono);
}

.stat-label {
    font-size: 0.875rem;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.cta-buttons {
    display: flex;
    gap: 1rem;
}

.btn-primary, .btn-secondary {
    padding: 1rem 2rem;
    border-radius: var(--border-radius);
    font-weight: 600;
    text-decoration: none;
    transition: var(--transition);
    display: inline-block;
    cursor: pointer;
    border: none;
    font-size: 1rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: var(--secondary-color);
    color: white;
    text-decoration: none;
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.btn-secondary {
    background: transparent;
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

.btn-secondary:hover {
    background: var(--primary-color);
    color: white;
    text-decoration: none;
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

/* Network Diagram */
.hero-visual {
    display: flex;
    justify-content: center;
    align-items: center;
}

.network-diagram {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    padding: 2rem;
    background: rgba(39, 39, 42, 0.5);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}

.layer {
    padding: 1rem 2rem;
    text-align: center;
    font-weight: 600;
    border-radius: 4px;
    transition: var(--transition);
    cursor: pointer;
    font-family: var(--font-mono);
    font-size: 0.875rem;
}

.layer[data-layer="application"] { background: #1e3a5f; color: #64b5f6; }
.layer[data-layer="transport"] { background: #3a1e5f; color: #ba68c8; }
.layer[data-layer="network"] { background: #1e5f3a; color: #81c784; }
.layer[data-layer="link"] { background: #5f3a1e; color: #ffb74d; }
.layer[data-layer="physical"] { background: #5f1e3a; color: #f48fb1; }

.layer:hover {
    transform: translateX(10px);
    box-shadow: var(--shadow-md);
}

/* Sections */
.section {
    padding: 5rem 0;
    background: var(--bg-primary);
}

.section:nth-child(even) {
    background: var(--bg-secondary);
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
}

/* Timeline */
.timeline {
    position: relative;
    padding: 2rem 0;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 50%;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--border-color);
    transform: translateX(-50%);
}

.timeline-item {
    position: relative;
    margin-bottom: 3rem;
    display: flex;
    align-items: flex-start;
}

.timeline-item:nth-child(odd) {
    flex-direction: row;
}

.timeline-item:nth-child(even) {
    flex-direction: row-reverse;
}

.timeline-year {
    flex: 0 0 100px;
    font-weight: 700;
    font-family: var(--font-mono);
    color: var(--primary-color);
    font-size: 1.25rem;
    padding: 1rem;
    background: var(--bg-tertiary);
    border-radius: var(--border-radius);
    text-align: center;
}

.timeline-content {
    flex: 1;
    padding: 0 2rem;
}

.timeline-content h3 {
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.tech-details {
    background: var(--code-bg);
    color: var(--code-color);
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-top: 1rem;
    font-family: var(--font-mono);
    font-size: 0.875rem;
}

/* Network Grid */
.network-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
    margin-bottom: 4rem;
}

.network-card {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.network-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.network-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.network-specs {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.spec {
    display: flex;
    justify-content: space-between;
    padding: 0.25rem 0;
    border-bottom: 1px solid var(--border-color);
}

.spec-label {
    font-weight: 600;
    color: var(--text-primary);
}

.spec-value {
    font-family: var(--font-mono);
    color: var(--primary-color);
}

/* Code Examples */
.code-example {
    margin-top: 1rem;
}

.code-example pre {
    background: var(--code-bg);
    color: var(--code-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.875rem;
    line-height: 1.4;
}

.code-example code {
    background: none;
    padding: 0;
}

/* Topologies */
.topologies {
    margin-top: 4rem;
}

.topology-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-top: 2rem;
}

.topology-item {
    text-align: center;
    padding: 2rem;
    background: var(--bg-secondary);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}

.topology-item h4 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.topology-diagram {
    width: 120px;
    height: 120px;
    margin: 1rem auto;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    position: relative;
    background: var(--bg-secondary);
}

.topology-diagram.star::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 20px;
    height: 20px;
    background: var(--primary-color);
    border-radius: 50%;
    transform: translate(-50%, -50%);
}

.topology-diagram.mesh {
    background: repeating-linear-gradient(
        45deg,
        var(--bg-secondary),
        var(--bg-secondary) 10px,
        var(--border-color) 10px,
        var(--border-color) 11px
    );
}

.topology-diagram.ring {
    border: 8px solid var(--primary-color);
    background: transparent;
}

.topology-diagram.bus {
    background: linear-gradient(
        to right,
        transparent 0%,
        var(--primary-color) 50%,
        transparent 100%
    );
}

/* TCP/IP Stack */
.tcpip-stack {
    margin: 3rem 0;
}

.stack-visualization {
    display: flex;
    flex-direction: column;
    gap: 0;
    border: 2px solid var(--border-color);
    border-radius: var(--border-radius);
    overflow: hidden;
    box-shadow: var(--shadow-lg);
}

.stack-visualization .layer {
    padding: 2rem;
    text-align: left;
    border-bottom: 1px solid var(--border-color);
    transition: var(--transition);
}

.stack-visualization .layer:last-child {
    border-bottom: none;
}

.stack-visualization .layer:hover {
    transform: translateX(10px);
}

.stack-visualization .layer.application { background: #1e3a5f; }
.stack-visualization .layer.transport { background: #3a1e5f; }
.stack-visualization .layer.network { background: #1e5f3a; }
.stack-visualization .layer.link { background: #5f3a1e; }

.stack-visualization h4 {
    margin-bottom: 1rem;
    color: var(--text-primary);
}

.layer-protocols {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
}

.protocol {
    background: var(--bg-tertiary);
    padding: 0.5rem 1rem;
    border-radius: 20px;
    font-size: 0.875rem;
    font-weight: 500;
    font-family: var(--font-mono);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
}

/* Protocol Details */
.protocol-details {
    margin-top: 3rem;
}

.protocol-section {
    margin-bottom: 3rem;
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
}

.protocol-section h3 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
}

.header-diagram pre {
    background: var(--code-bg);
    color: var(--code-color);
    padding: 1.5rem;
    border-radius: var(--border-radius);
    overflow-x: auto;
    font-family: var(--font-mono);
    font-size: 0.875rem;
    line-height: 1.4;
    margin-bottom: 1.5rem;
}

.field-descriptions {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 1rem;
}

.field {
    padding: 1rem;
    background: var(--bg-secondary);
    border-radius: var(--border-radius);
    border-left: 4px solid var(--primary-color);
}

.field strong {
    color: var(--text-primary);
    display: block;
    margin-bottom: 0.25rem;
}

/* Handshake Diagram */
.handshake-diagram {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    margin-top: 2rem;
}

.handshake-step {
    display: flex;
    align-items: center;
    gap: 2rem;
}

.packet {
    padding: 1rem 1.5rem;
    border-radius: var(--border-radius);
    font-family: var(--font-mono);
    font-weight: 600;
    min-width: 200px;
    text-align: center;
    box-shadow: var(--shadow-md);
}

.packet.syn { background: #1e3a5f; color: #64b5f6; }
.packet.syn-ack { background: #3a1e5f; color: #ba68c8; }
.packet.ack { background: #1e5f3a; color: #81c784; }

.packet-type {
    display: block;
    font-size: 1.125rem;
    margin-bottom: 0.25rem;
}

.packet-flags {
    font-size: 0.875rem;
    opacity: 0.8;
}

/* Protocol Grid */
.protocol-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.protocol-card {
    background: var(--bg-secondary);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--border-color);
    transition: var(--transition);
}

.protocol-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-xl);
}

.protocol-card h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.protocol-info {
    margin-bottom: 1rem;
}

.protocol-specs {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.spec {
    background: var(--bg-tertiary);
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    font-size: 0.75rem;
    font-weight: 500;
    font-family: var(--font-mono);
    color: var(--text-secondary);
}

/* Footer */
footer {
    background: var(--bg-tertiary);
    color: var(--text-primary);
    padding: 3rem 0 1rem;
    border-top: 1px solid var(--border-color);
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 2rem;
    margin-bottom: 2rem;
}

.footer-section h3,
.footer-section h4 {
    color: var(--text-primary);
    margin-bottom: 1rem;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 0.5rem;
}

.footer-section a {
    color: var(--text-secondary);
    transition: var(--transition);
}

.footer-section a:hover {
    color: var(--primary-color);
}

.footer-bottom {
    border-top: 1px solid var(--border-color);
    padding-top: 1rem;
    text-align: center;
    color: var(--text-muted);
}

/* Responsive Design */
@media (max-width: 768px) {
    .nav-menu {
        display: none;
    }
    
    .hamburger {
        display: flex;
    }
    
    .hero-content {
        grid-template-columns: 1fr;
        gap: 2rem;
        text-align: center;
    }
    
    .hero h1 {
        font-size: 2.5rem;
    }
    
    .hero-stats {
        justify-content: center;
    }
    
    .cta-buttons {
        justify-content: center;
        flex-wrap: wrap;
    }
    
    .timeline::before {
        left: 20px;
    }
    
    .timeline-item {
        flex-direction: row !important;
        padding-left: 40px;
    }
    
    .timeline-year {
        position: absolute;
        left: 0;
        flex: 0 0 auto;
    }
    
    .network-grid,
    .protocol-grid,
    .topology-grid {
        grid-template-columns: 1fr;
    }
    
    .field-descriptions {
        grid-template-columns: 1fr;
    }
    
    .handshake-step {
        flex-direction: column;
        text-align: center;
    }
}

/* Smooth Scrolling */
html {
    scroll-behavior: smooth;
}

/* Selection Colors */
::selection {
    background: var(--primary-color);
    color: white;
}

/* Focus States */
a:focus,
button:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Loading States */
.loading {
    opacity: 0.6;
    pointer-events: none;
}

/* Print Styles */
@media print {
    .navbar,
    .hamburger,
    .cta-buttons {
        display: none;
    }
    
    .hero {
        min-height: auto;
        padding: 2rem 0;
    }
    
    .section {
        page-break-inside: avoid;
    }
}