:root {
    /* Core Colors */
    --primary: #0057b8;
    --primary-dark: #003d80;
    --secondary: #1976d2;
    --accent: #00a464;

    /* Light Theme */
    --bg: #fafafa;
    --surface: #ffffff;
    --surface2: #f8f9fa;
    --text: #202124;
    --text-light: #5f6368;
    --border: #e6e8ec;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
    --shadow-hover: 0 10px 30px rgba(0, 0, 0, 0.1);

    /* Radius & Spacing */
    --radius: 14px;
    --radius-sm: 8px;
}

[data-theme="dark"] {
    --bg: #0f1117;
    --surface: #171b24;
    --surface2: #1e2330;
    --text: #e8eaed;
    --text-light: #9aa0a6;
    --border: #2d333f;
    --shadow: 0 2px 8px rgba(0, 0, 0, 0.3);
    --shadow-hover: 0 12px 32px rgba(0, 0, 0, 0.4);
}

/* ====================== Base ====================== */
*,
*::before,
*::after { box-sizing: border-box; }

body {
    margin: 0;
    font-family: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background: var(--bg);
    color: var(--text);
    line-height: 1.75;
    font-size: 1.02rem;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 1280px;
    margin: 0 auto;
    padding: 0 24px;
}

/* ====================== Header ====================== */
.site-header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    backdrop-filter: blur(12px);
}

.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 24px;
}

.logo a {
    font-size: 1.35rem;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
}

nav ul {
    display: flex;
    list-style: none;
    gap: 28px;
    margin: 0;
    padding: 0;
}

nav ul li a {
    font-weight: 500;
    transition: color 0.2s;
}

nav ul li a:hover {
    color: var(--primary);
}

/* Hamburger Menu */
.mobile-menu {
    display: none;
    background: none;
    border: none;
    font-size: 1.8rem;
    cursor: pointer;
}

/* ====================== Hero ====================== */
.hero {
    padding: 110px 0 130px;
    background: linear-gradient(135deg, #f8fbff 0%, #f0f4ff 100%);
}

[data-theme="dark"] .hero {
    background: linear-gradient(135deg, #171b24 0%, #0f1117 100%);
}

.hero-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 60px;
    align-items: center;
}

.profile-image {
    width: 100%;
    max-width: 340px;
    height: auto;
    border-radius: 24px;
    box-shadow: var(--shadow-hover);
    border: 10px solid var(--surface);
}


/* =========================================================
   AI Safety / Safety OS
========================================================= */

.safety-os-section {
    position: relative;
}

.safety-os-section .section-kicker {
    display: inline-block;
    margin-bottom: 8px;
    padding: 5px 12px;

    border-radius: 999px;

    background: rgba(220, 38, 38, 0.08);
    color: #b91c1c;

    font-size: 0.78rem;
    font-weight: 700;
    letter-spacing: 0.06em;
    text-transform: uppercase;
}

.safety-os-section .portal-card {
    border-top: 3px solid #dc2626;
}

.safety-os-section .portal-card:hover {
    transform: translateY(-4px);
}

.featured-tag {
    font-weight: 700 !important;
    border: 1px solid rgba(220, 38, 38, 0.25) !important;
}

.knowledge-graph {
    padding: 38px;
    border-radius: 16px;

    background: var(--surface);

    text-align: center;
}

.kg-root {
    font-size: 1.35rem;
}

.kg-arrow {
    padding: 10px;
    color: var(--primary);
    font-size: 1.3rem;
}

.kg-layer {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: 12px;
}

.kg-layer span,
.kg-layer strong {
    padding: 9px 15px;
    border-radius: 8px;
    background: var(--background, #f8fafc);
}

.kg-highlight strong {
    padding: 12px 22px;
    border: 1px solid var(--primary);
    font-size: 1.05rem;
}

@media (max-width: 768px) {

    .knowledge-graph {
        padding: 24px 16px;
    }

    .kg-layer {
        flex-direction: column;
    }
}


/* =========================================================
   Industrial AI Research Architecture
========================================================= */

.research-architecture-section {
  padding: 72px 20px;
}

.research-architecture-container {
  max-width: 1280px;
  margin: 0 auto;
}

.research-architecture-header {
  max-width: 850px;
  margin: 0 auto 48px;
  text-align: center;
}

.research-architecture-header h2 {
  margin: 10px 0 14px;
  font-size: clamp(1.8rem, 3vw, 2.6rem);
  color: var(--text-primary, #0f172a);
}

.research-architecture-header p {
  line-height: 1.7;
  color: var(--text-secondary, #64748b);
}

.section-kicker {
  display: inline-block;
  padding: 5px 12px;
  border-radius: 999px;

  background: rgba(37, 99, 235, 0.08);
  color: #2563eb;

  font-size: 0.75rem;
  font-weight: 700;
  letter-spacing: 0.08em;
}


/* ================= NODE ================= */

.architecture-node {
  position: relative;

  padding: 18px 20px;

  background: var(--surface, #ffffff);
  border: 1px solid #e2e8f0;
  border-radius: 12px;

  box-shadow:
    0 2px 5px rgba(15, 23, 42, 0.04),
    0 8px 20px rgba(15, 23, 42, 0.04);

  text-align: center;

  transition:
    transform 0.2s ease,
    box-shadow 0.2s ease;
}

.architecture-node:hover {
  transform: translateY(-3px);

  box-shadow:
    0 5px 14px rgba(15, 23, 42, 0.08),
    0 14px 32px rgba(15, 23, 42, 0.06);
}

.architecture-node strong {
  display: block;

  color: var(--text-primary, #0f172a);

  font-size: 1rem;
}

.architecture-node small {
  display: block;

  margin-top: 6px;

  color: var(--text-secondary, #64748b);

  font-size: 0.75rem;
  line-height: 1.5;
}

.node-label {
  display: block;

  margin-bottom: 6px;

  color: #64748b;

  font-size: 0.64rem;
  font-weight: 700;

  letter-spacing: 0.08em;
}


/* ================= ROOT ================= */

.architecture-root {
  display: flex;
  justify-content: center;
}

.node-root {
  min-width: 240px;

  border: 2px solid #2563eb;

  background:
    linear-gradient(
      135deg,
      rgba(37, 99, 235, 0.08),
      rgba(14, 165, 233, 0.05)
    );
}

.node-root strong {
  color: #1d4ed8;
  font-size: 1.35rem;
}


/* ================= CONNECTOR ================= */

.vertical-line,
.column-line {
  width: 2px;

  margin: 0 auto;

  background: #cbd5e1;
}

.vertical-line {
  height: 42px;
}

.column-line {
  height: 26px;
}


/* ================= THREE COLUMNS ================= */

.architecture-branches {
  position: relative;

  display: grid;

  grid-template-columns:
    minmax(230px, 1fr)
    minmax(340px, 1.45fr)
    minmax(230px, 1fr);

  gap: 28px;
}


/* top horizontal connector */

.architecture-branches::before {
  content: "";

  position: absolute;

  top: 0;
  left: 16.66%;
  right: 16.66%;

  height: 2px;

  background: #cbd5e1;

  transform: translateY(-1px);
}


.architecture-column {
  position: relative;

  display: flex;
  flex-direction: column;

  align-items: stretch;
}

.architecture-column::before {
  content: "";

  width: 2px;
  height: 24px;

  margin: 0 auto;

  background: #cbd5e1;
}


/* ================= DOMAIN NODES ================= */

.node-domain {
  min-height: 90px;

  display: flex;
  flex-direction: column;

  justify-content: center;
}

.vision-node {
  border-top: 4px solid #2563eb;
}

.safety-node {
  border-top: 4px solid #dc2626;
}

.agent-node {
  border-top: 4px solid #7c3aed;
}

.node-domain strong {
  font-size: 1.15rem;
}


/* ================= SYSTEM ================= */

.node-system {
  border: 1px solid #94a3b8;

  background: #f8fafc;
}

.node-system strong {
  font-size: 1.08rem;
}


/* Safety OS emphasis */

.safety-os {
  border: 2px solid #dc2626;

  background:
    linear-gradient(
      135deg,
      rgba(220, 38, 38, 0.07),
      rgba(249, 115, 22, 0.04)
    );
}

.safety-os strong {
  color: #b91c1c;
  font-size: 1.2rem;
}


/* ================= MODULES ================= */

.subsystem-grid {
  display: grid;

  grid-template-columns: repeat(2, 1fr);

  gap: 12px;
}

.safety-components {
  display: grid;

  grid-template-columns: repeat(3, 1fr);

  gap: 10px;
}

.node-module {
  min-height: 86px;

  display: flex;
  flex-direction: column;

  justify-content: center;
}


/* ================= SAFE ACTION ================= */

.node-action {
  border: 2px solid #059669;

  background:
    linear-gradient(
      135deg,
      rgba(5, 150, 105, 0.08),
      rgba(16, 185, 129, 0.04)
    );
}

.node-action strong {
  color: #047857;
  font-size: 1.1rem;
}


/* ================= EVIDENCE ================= */

.evidence-grid {
  display: grid;

  grid-template-columns: repeat(3, 1fr);

  gap: 10px;
}

.node-evidence {
  border-top: 3px solid #0f766e;
}


/* ================= SUMMARY ================= */

.architecture-summary {
  display: grid;

  grid-template-columns: repeat(3, 1fr);

  gap: 18px;

  margin-top: 54px;
  padding-top: 28px;

  border-top: 1px solid #e2e8f0;
}

.architecture-summary div {
  text-align: center;
}

.architecture-summary strong {
  display: block;

  margin-bottom: 4px;

  color: #0f172a;
}

.architecture-summary span {
  color: #64748b;

  font-size: 0.82rem;
}


/* =========================================================
   Responsive
========================================================= */

@media (max-width: 960px) {

  .architecture-branches {
    grid-template-columns: 1fr;
    gap: 36px;
  }

  .architecture-branches::before {
    display: none;
  }

  .architecture-column::before {
    height: 18px;
  }

  .safety-components {
    grid-template-columns: 1fr;
  }

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

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

  .architecture-summary {
    grid-template-columns: 1fr;
  }

}


@media (max-width: 640px) {

  .research-architecture-section {
    padding: 48px 14px;
  }

  .research-architecture-header {
    margin-bottom: 32px;
  }

  .architecture-node {
    padding: 15px;
  }

}


/* ====================== Cards ====================== */
.portal-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
    box-shadow: var(--shadow);
    transition: all 0.3s cubic-bezier(0.4, 0.0, 0.2, 1);
    height: 100%;
    display: flex;
    flex-direction: column;
}

.portal-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-hover);
}

.card-body {
    padding: 26px;
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.portal-card h3 {
    margin: 0 0 8px 0;
    font-size: 1.28rem;
    line-height: 1.35;
}

.card-summary {
    color: var(--text-light);
    flex: 1;
    font-size: 0.97rem;
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
}

/* Badge */
.badge {
    padding: 4px 12px;
    border-radius: 20px;
    font-size: 0.82rem;
    font-weight: 600;
}

.status.active { background: #00a464; color: white; }
.status { background: #e0e0e0; color: #555; }

/* ====================== Buttons ====================== */
.btn {
    display: inline-block;
    padding: 14px 28px;
    border-radius: var(--radius-sm);
    background: var(--primary);
    color: white;
    font-weight: 600;
    transition: all 0.25s;
    text-align: center;
}

.btn:hover {
    background: var(--primary-dark);
    transform: translateY(-2px);
    box-shadow: 0 8px 20px rgba(0, 87, 184, 0.35);
}

/* ====================== Tag Cloud ====================== */
.tag-cloud {
    display: flex;
    flex-wrap: wrap;
    gap: 12px;
}

.tag-cloud span {
    background: #e3f0ff;
    color: var(--primary);
    padding: 8px 18px;
    border-radius: 9999px;
    font-size: 0.95rem;
    transition: all 0.2s;
}

.tag-cloud span:hover {
    background: var(--primary);
    color: white;
    transform: scale(1.05);
}

/* ====================== Footer ====================== */
.site-footer {
    margin-top: 120px;
    padding: 80px 0 40px;
    background: #0f1117;
    color: #e8eaed;
}

.footer-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
    gap: 40px;
    margin-bottom: 60px;
}

/* ====================== Responsive ====================== */
@media (max-width: 992px) {
    .hero-grid {
        grid-template-columns: 1fr;
        text-align: center;
        gap: 50px;
    }
    .profile-image { margin: 0 auto; }
}

@media (max-width: 768px) {
    h1 { font-size: 2.45rem; }
    h2 { font-size: 1.9rem; }
    
    .hero { padding: 80px 0 90px; }
    
    nav ul {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--surface);
        padding: 20px;
        box-shadow: var(--shadow);
    }
    
    .mobile-menu { display: block; }
}

/* ====================== Additional Polish ====================== */
section { padding: 80px 0; }

.hub-section, .featured-section {
    background: var(--surface2);
}

.knowledge-section { background: var(--bg); }

/* Focus & Accessibility */
a:focus, button:focus, .btn:focus {
    outline: 3px solid #4da3ff;
    outline-offset: 4px;
}

html { scroll-behavior: smooth; }

/* Utility */
.text-center { text-align: center; }
.mt-0 { margin-top: 0; }

/* ====================== Mobile Menu ====================== */
.mobile-menu {
    display: none;
    background: none;
    border: none;
    font-size: 1.8rem;
    cursor: pointer;
    padding: 8px;
    color: var(--text);
}

@media (max-width: 768px) {
    .mobile-menu {
        display: block;
    }

    nav#main-nav ul {
        display: none;
        flex-direction: column;
        position: absolute;
        top: 100%;
        left: 0;
        right: 0;
        background: var(--surface);
        border-top: 1px solid var(--border);
        box-shadow: var(--shadow);
        padding: 20px 24px;
        gap: 16px;
    }

    nav#main-nav ul.show {
        display: flex;
    }

    nav#main-nav ul li a {
        font-size: 1.1rem;
        padding: 8px 0;
    }
}

/* Header container adjustment */
.site-header .container {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 16px 24px;
}