/* ============================================================
   CSS CUSTOM PROPERTIES
   ============================================================ */
:root {
    --primary: #2563eb;
    --primary-dark: #1d4ed8;

    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;
    --border-color: #e2e8f0;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
}

[data-theme="dark"] {
    --primary: #60a5fa;
    --primary-dark: #3b82f6;

    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-tertiary: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --border-color: #334155;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3), 0 2px 4px -2px rgba(0, 0, 0, 0.3);
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    font-size: 1rem;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 0 1.5rem;
}

/* Accessibility */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

.skip-link {
    position: absolute;
    top: -100%;
    left: 1rem;
    background: var(--primary);
    color: #fff;
    padding: 0.5rem 1rem;
    border-radius: 0 0 4px 4px;
    font-size: 0.875rem;
    font-weight: 600;
    text-decoration: none;
    z-index: 9999;
}

.skip-link:focus {
    top: 0;
}

[data-theme="dark"] .skip-link {
    color: var(--bg-primary);
}

/* ============================================================
   NAVIGATION
   ============================================================ */
header {
    background-color: var(--bg-primary);
    border-bottom: 1px solid var(--border-color);
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 100;
}

header nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    height: 60px;
}

.logo {
    font-size: 1.1rem;
    font-weight: 800;
    letter-spacing: -0.02em;
    text-decoration: none;
}

.logo-rogo { color: var(--text-primary); }
.logo-labs { color: var(--primary); }

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

.nav-links a {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.15s;
}

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

.header-controls {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.theme-toggle {
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0.4rem 0.6rem;
    font-size: 0.875rem;
    transition: color 0.15s, border-color 0.15s;
}

.theme-toggle:hover {
    color: var(--text-primary);
    border-color: var(--text-secondary);
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0.4rem 0.6rem;
    font-size: 0.875rem;
}

/* ============================================================
   HERO
   ============================================================ */
.hero {
    padding: 8rem 0 5rem;
    border-bottom: 1px solid var(--border-color);
}

.hero-eyebrow {
    font-size: 0.72rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--primary);
    font-weight: 600;
    margin-bottom: 1.25rem;
}

.hero h1 {
    font-size: clamp(1.75rem, 3.5vw, 2.25rem);
    font-weight: 800;
    line-height: 1.2;
    letter-spacing: -0.03em;
    color: var(--text-primary);
    margin-bottom: 1.25rem;
}

.hero h1 .accent {
    color: var(--primary);
}

.hero-sub {
    font-size: 1.05rem;
    color: var(--text-secondary);
    line-height: 1.65;
    margin-bottom: 2.25rem;
}

.hero-actions {
    display: flex;
    gap: 0.875rem;
    flex-wrap: wrap;
}

.btn {
    display: inline-block;
    background: var(--primary);
    color: #ffffff;
    padding: 0.65rem 1.35rem;
    border-radius: 6px;
    font-size: 0.875rem;
    font-weight: 600;
    text-decoration: none;
    transition: background 0.15s, opacity 0.15s;
    cursor: pointer;
    border: none;
}

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

.btn-ghost {
    display: inline-block;
    background: none;
    border: 1px solid var(--border-color);
    color: var(--text-secondary);
    padding: 0.65rem 1.35rem;
    border-radius: 6px;
    font-size: 0.875rem;
    font-weight: 500;
    text-decoration: none;
    transition: border-color 0.15s, color 0.15s;
}

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

/* ============================================================
   SECTIONS (shared)
   ============================================================ */
.section {
    padding: 4rem 0;
    border-bottom: 1px solid var(--border-color);
}

.section-label {
    font-size: 0.68rem;
    letter-spacing: 0.12em;
    text-transform: uppercase;
    color: var(--primary);
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.section-title {
    font-size: clamp(1.35rem, 3vw, 1.6rem);
    font-weight: 800;
    letter-spacing: -0.02em;
    color: var(--text-primary);
    margin-bottom: 0.4rem;
}

.section-sub {
    font-size: 0.9rem;
    color: var(--text-secondary);
    margin-bottom: 2.5rem;
    max-width: 560px;
}

/* ============================================================
   ABOUT
   ============================================================ */
.about-text {
    max-width: 660px;
}

.about-text p {
    font-size: 0.9rem;
    color: var(--text-secondary);
    line-height: 1.75;
    margin-bottom: 1.1rem;
}

.about-text p:last-of-type {
    margin-bottom: 0;
}

.about-text strong {
    color: var(--text-primary);
    font-weight: 600;
}

.about-text em {
    color: var(--primary);
    font-style: normal;
    font-weight: 500;
}

.about-sig {
    font-size: 0.875rem;
    color: var(--text-muted);
    margin-top: 1.5rem;
}

/* ============================================================
   TOOLKIT GRID
   ============================================================ */
.toolkit-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1rem;
}

.tool-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.25rem;
    transition: box-shadow 0.15s, border-color 0.15s;
}

.tool-card:hover {
    box-shadow: var(--shadow-md);
    border-color: var(--primary);
}

.tool-name {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 0.35rem;
}

.tool-desc {
    font-size: 0.78rem;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 0.75rem;
}

.tool-tag {
    display: inline-block;
    background: #eff6ff;
    color: var(--primary);
    font-size: 0.65rem;
    padding: 0.2rem 0.5rem;
    border-radius: 4px;
    font-weight: 500;
    margin-bottom: 0.75rem;
}

[data-theme="dark"] .tool-tag {
    background: #1e3a5f;
}

.tool-links {
    display: flex;
    gap: 0.75rem;
    align-items: center;
}

.tool-link {
    font-size: 0.78rem;
    color: var(--primary);
    font-weight: 600;
    text-decoration: none;
    transition: opacity 0.15s;
}

.tool-link:hover {
    opacity: 0.75;
}

.tool-link-gh {
    font-size: 0.78rem;
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.15s;
}

.tool-link-gh:hover {
    color: var(--text-secondary);
}

/* ============================================================
   TALKS TIMELINE
   ============================================================ */
.timeline {
    position: relative;
    padding-left: 1.75rem;
}

.timeline::before {
    content: '';
    position: absolute;
    left: 0.5rem;
    top: 0.4rem;
    bottom: 0;
    width: 2px;
    background: var(--border-color);
    border-radius: 2px;
}

.talk-item {
    position: relative;
    margin-bottom: 2.25rem;
}

.talk-item:last-child {
    margin-bottom: 0;
}

.talk-item::before {
    content: '';
    position: absolute;
    left: calc(-1.75rem + 0.5rem + 5px);
    top: 0.35rem;
    width: 10px;
    height: 10px;
    background: var(--primary);
    border-radius: 50%;
    border: 2px solid var(--bg-primary);
    box-shadow: 0 0 0 2px var(--primary);
}

.talk-meta {
    font-size: 0.72rem;
    color: var(--text-muted);
    margin-bottom: 0.25rem;
}

.talk-venue {
    color: var(--primary);
    font-weight: 600;
}

a.talk-venue {
    text-decoration: none;
}

a.talk-venue:hover {
    text-decoration: underline;
}

.talk-title {
    font-size: 0.95rem;
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1.35;
    margin-bottom: 0.4rem;
}

.talk-abstract {
    font-size: 0.82rem;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 0.6rem;
    max-width: 680px;
}

.talk-links {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.talk-link {
    display: inline-block;
    background: #eff6ff;
    color: var(--primary);
    font-size: 0.72rem;
    padding: 0.25rem 0.6rem;
    border-radius: 4px;
    font-weight: 500;
    text-decoration: none;
    transition: opacity 0.15s;
}

.talk-link:hover {
    opacity: 0.75;
}

[data-theme="dark"] .talk-link {
    background: #1e3a5f;
}

.talk-link-video {
    display: inline-block;
    background: #fef3c7;
    color: #92400e;
    font-size: 0.72rem;
    padding: 0.25rem 0.6rem;
    border-radius: 4px;
    font-weight: 500;
    text-decoration: none;
    transition: opacity 0.15s;
}

[data-theme="dark"] .talk-link-video {
    background: #451a03;
    color: #fcd34d;
}

.talk-link-video:hover {
    opacity: 0.75;
}

/* ============================================================
   FOOTER
   ============================================================ */
footer {
    background: var(--bg-secondary);
    padding: 1.75rem 0;
}

.footer-inner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.footer-copy {
    font-size: 0.78rem;
    color: var(--text-muted);
}

.footer-links {
    display: flex;
    gap: 1.25rem;
}

.footer-links a {
    font-size: 0.78rem;
    color: var(--text-secondary);
    text-decoration: none;
    transition: color 0.15s;
}

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

/* ============================================================
   RESPONSIVE
   ============================================================ */
@media (max-width: 900px) {
    .toolkit-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

@media (max-width: 640px) {
    .hero {
        padding: 6rem 0 3.5rem;
    }

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

    .nav-links {
        display: none;
        position: absolute;
        top: 60px;
        left: 0;
        right: 0;
        background: var(--bg-primary);
        border-bottom: 1px solid var(--border-color);
        flex-direction: column;
        gap: 0;
        padding: 0.5rem 0;
    }

    .nav-links.active {
        display: flex;
    }

    .nav-links a {
        padding: 0.75rem 1.5rem;
        width: 100%;
    }

    .mobile-menu-btn {
        display: block;
    }

    .footer-inner {
        flex-direction: column;
        align-items: flex-start;
        gap: 0.75rem;
    }
}