/* ===== Variables ===== */
:root {
    --color-bg: #0a0a0f;
    --color-bg-secondary: #12121a;
    --color-text: #e4e4e7;
    --color-text-muted: #71717a;
    --color-primary: #6366f1;
    --color-primary-light: #818cf8;
    --color-accent: #22d3ee;
    --color-border: #27272a;
    --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    --font-mono: 'JetBrains Mono', monospace;
    --radius: 12px;
    --transition: 0.2s ease;
}

/* ===== Reset & Base ===== */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

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

a {
    color: inherit;
    text-decoration: none;
}

ul {
    list-style: none;
}

/* ===== Header & Nav ===== */
.header {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    z-index: 100;
    background: rgba(10, 10, 15, 0.8);
    backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--color-border);
}

.nav {
    max-width: 1200px;
    margin: 0 auto;
    padding: 1rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-text);
}

.logo span {
    color: var(--color-primary);
}

.nav-links {
    display: flex;
    gap: 2rem;
}

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

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

/* ===== Hero ===== */
.hero {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 6rem 2rem 4rem;
    background:
        radial-gradient(ellipse at 50% 0%, rgba(99, 102, 241, 0.15) 0%, transparent 50%),
        var(--color-bg);
}

.hero-content {
    max-width: 800px;
    text-align: center;
}

.hero h1 {
    font-size: clamp(2.5rem, 8vw, 4.5rem);
    font-weight: 700;
    letter-spacing: -0.02em;
    margin-bottom: 1.5rem;
    background: linear-gradient(135deg, var(--color-text) 0%, var(--color-primary-light) 100%);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.hero-subtitle {
    font-size: 1.25rem;
    color: var(--color-text-muted);
    max-width: 600px;
    margin: 0 auto 3rem;
}

.hero-stats {
    display: flex;
    justify-content: center;
    gap: 4rem;
}

.stat {
    display: flex;
    flex-direction: column;
    align-items: center;
}

.stat-number {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--color-primary-light);
}

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

/* ===== Sections ===== */
.section {
    padding: 6rem 2rem;
    max-width: 1200px;
    margin: 0 auto;
}

.section-title {
    font-size: 2rem;
    font-weight: 600;
    margin-bottom: 3rem;
    text-align: center;
    position: relative;
}

.section-title::after {
    content: '';
    display: block;
    width: 60px;
    height: 3px;
    background: var(--color-primary);
    margin: 1rem auto 0;
    border-radius: 2px;
}

/* ===== Section Intro ===== */
.section-intro {
    text-align: center;
    color: var(--color-text-muted);
    font-size: 1.1rem;
    max-width: 700px;
    margin: -1.5rem auto 2rem;
}

.section-intro strong {
    color: var(--color-accent);
}

/* ===== Formula Block ===== */
.formula-block {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 1.5rem 2rem;
    text-align: center;
    max-width: 600px;
    margin: 0 auto 3rem;
}

.formula-block code {
    font-family: var(--font-mono);
    font-size: 1.1rem;
    color: var(--color-primary-light);
    display: block;
    margin-bottom: 0.75rem;
}

.formula-block p {
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

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

.research-card {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 2rem;
    transition: transform var(--transition), border-color var(--transition);
}

.research-card:hover {
    transform: translateY(-4px);
    border-color: var(--color-primary);
}

.card-icon {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.research-card h3 {
    font-size: 1.25rem;
    margin-bottom: 0.75rem;
}

.research-card p {
    color: var(--color-text-muted);
    font-size: 0.95rem;
}

/* ===== Papers Grid ===== */
.papers-section {
    background: var(--color-bg-secondary);
    max-width: 100%;
    padding: 6rem calc((100% - 1200px) / 2 + 2rem);
}

.papers-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 2rem;
}

.paper-card {
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 2rem;
    position: relative;
    transition: border-color var(--transition);
}

.paper-card:hover {
    border-color: var(--color-primary);
}

.paper-badge {
    position: absolute;
    top: -12px;
    right: 24px;
    background: var(--color-primary);
    color: white;
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.25rem 0.75rem;
    border-radius: 4px;
    letter-spacing: 0.05em;
}

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

.paper-subtitle {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.paper-abstract {
    color: var(--color-text-muted);
    font-size: 0.95rem;
    margin-bottom: 1.5rem;
    line-height: 1.7;
}

.paper-highlights {
    margin-bottom: 1.5rem;
}

.paper-highlights li {
    position: relative;
    padding-left: 1.25rem;
    margin-bottom: 0.5rem;
    font-size: 0.9rem;
    color: var(--color-text-muted);
}

.paper-highlights li::before {
    content: '→';
    position: absolute;
    left: 0;
    color: var(--color-accent);
}

.paper-links {
    display: flex;
    gap: 1rem;
}

/* ===== Companion Card ===== */
.companion-card {
    background: linear-gradient(135deg, var(--color-bg) 0%, rgba(99, 102, 241, 0.1) 100%);
    border-color: var(--color-primary);
    margin-bottom: 2rem;
    text-align: center;
}

.companion-card .paper-badge {
    background: var(--color-accent);
}

.companion-card .paper-links {
    justify-content: center;
}

/* ===== Buttons ===== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 0.75rem 1.5rem;
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: 8px;
    transition: all var(--transition);
    cursor: pointer;
    border: none;
}

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

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

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

.btn-secondary:hover {
    border-color: var(--color-primary);
    color: var(--color-primary-light);
}

/* ===== Code Block ===== */
.code-block {
    background: var(--color-bg-secondary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 2rem;
    overflow-x: auto;
    max-width: 800px;
    margin: 0 auto;
}

.code-block pre {
    margin: 0;
}

.code-block code {
    font-family: var(--font-mono);
    font-size: 0.9rem;
    line-height: 1.8;
    color: var(--color-text);
}

.code-block .comment {
    color: var(--color-text-muted);
}

.code-note {
    text-align: center;
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin-top: 1.5rem;
}

/* ===== Contact ===== */
.contact-section {
    text-align: center;
}

.contact-content p {
    color: var(--color-text-muted);
    margin-bottom: 1rem;
}

.contact-email {
    display: inline-block;
    font-size: 1.25rem;
    color: var(--color-primary-light);
    margin-bottom: 2rem;
    transition: color var(--transition);
}

.contact-email:hover {
    color: var(--color-accent);
}

.social-links {
    display: flex;
    justify-content: center;
    gap: 1rem;
}

.social-link {
    padding: 0.5rem 1rem;
    border: 1px solid var(--color-border);
    border-radius: 6px;
    font-size: 0.875rem;
    color: var(--color-text-muted);
    transition: all var(--transition);
}

.social-link:hover {
    border-color: var(--color-primary);
    color: var(--color-text);
}

/* ===== Footer ===== */
.footer {
    border-top: 1px solid var(--color-border);
    padding: 3rem 2rem;
    text-align: center;
}

.footer p {
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

.footer-quote {
    font-style: italic;
    margin-top: 1rem;
    max-width: 600px;
    margin-left: auto;
    margin-right: auto;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .nav-links {
        display: none;
    }

    .hero-stats {
        flex-direction: column;
        gap: 2rem;
    }

    .papers-grid {
        grid-template-columns: 1fr;
    }

    .paper-links {
        flex-direction: column;
    }
}