/* HARMONIC - Main Stylesheet
   Clean Academic/Research Design System
   ===================================== */

/* CSS Variables - Subtle Color Palette */
:root {
  /* Primary Colors - Soft Blue-Gray */
  --color-primary: #374151;
  --color-secondary: #4b5563;
  --color-accent: #3b82f6;
  --color-accent-hover: #2563eb;
  --color-link: #3b82f6;

  /* Background Colors - Subtle warm grays */
  --color-bg-primary: #fafafa;
  --color-bg-secondary: #f3f4f6;
  --color-bg-tertiary: #e5e7eb;
  --color-bg-card: #ffffff;

  /* Text Colors */
  --color-text-primary: #1f2937;
  --color-text-secondary: #4b5563;
  --color-text-tertiary: #6b7280;
  --color-text-muted: #9ca3af;

  /* Borders & Shadows */
  --color-border: #e5e7eb;
  --color-border-hover: #d1d5db;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -1px rgba(0, 0, 0, 0.04);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -2px rgba(0, 0, 0, 0.03);

  /* Typography */
  --font-primary: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'Consolas', 'Monaco', 'Andale Mono', monospace;

  /* Spacing */
  --space-xs: 0.25rem;
  --space-sm: 0.5rem;
  --space-md: 1rem;
  --space-lg: 1.5rem;
  --space-xl: 2rem;
  --space-2xl: 3rem;
  --space-3xl: 4rem;

  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.2s ease;
  --transition-slow: 0.3s ease;

  /* Container */
  --container-max: 1200px;
  --container-narrow: 800px;
}

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

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  font-family: var(--font-primary);
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text-primary);
  background-color: var(--color-bg-primary);
  overflow-x: hidden;
  min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  color: var(--color-primary);
}

h1 { font-size: 2.5rem; }
h2 { font-size: 1.75rem; }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.125rem; }

p {
  margin-bottom: var(--space-md);
  color: var(--color-text-secondary);
  line-height: 1.7;
}

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

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

/* Container */
.container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

.container-narrow {
  max-width: var(--container-narrow);
  margin: 0 auto;
  padding: 0 var(--space-xl);
}

/* ==========================================
   NAVIGATION
   ========================================== */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(255, 255, 255, 0.95);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--color-border);
  height: 64px;
}

.nav.scrolled {
  background: rgba(255, 255, 255, 0.98);
  box-shadow: var(--shadow-md);
}

.nav-container {
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-xl);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.nav-logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: 0.5px;
  display: flex;
  align-items: center;
}

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

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

.nav-logo-img {
  height: 60px;
  width: auto;
}

.nav-menu {
  display: flex;
  align-items: center;
  list-style: none;
  gap: var(--space-xs);
  margin: 0;
  padding: 0;
}

.nav-item {
  position: relative;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--color-text-secondary);
  font-size: 1.0rem;
  font-weight: 500;
  padding: 10px 16px;
  border-radius: var(--radius-sm);
  transition: all var(--transition-fast);
  white-space: nowrap;
}

.nav-link:hover {
  color: var(--color-accent);
  background: var(--color-bg-secondary);
  text-decoration: none;
}

.nav-link.active {
  color: var(--color-accent);
}

.nav-dropdown-toggle {
  background: transparent;
  border: none;
  cursor: pointer;
  font-family: inherit;
}

.nav-dropdown-toggle i {
  font-size: 0.65rem;
  transition: transform var(--transition-fast);
}

.nav-dropdown:hover .nav-dropdown-toggle i,
.nav-dropdown.open .nav-dropdown-toggle i {
  transform: rotate(180deg);
}

.nav-submenu {
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 220px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-lg);
  list-style: none;
  padding: var(--space-sm) 0;
  margin-top: 4px;
  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition: all var(--transition-fast);
  z-index: 1001;
}

.nav-dropdown:hover .nav-submenu,
.nav-dropdown.open .nav-submenu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.nav-sublink {
  display: block;
  padding: 10px 20px;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  font-weight: 500;
  transition: all var(--transition-fast);
}

.nav-sublink:hover {
  color: var(--color-accent);
  background: var(--color-bg-secondary);
  text-decoration: none;
}

.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  cursor: pointer;
  padding: var(--space-sm);
}

.nav-toggle .bar {
  width: 24px;
  height: 2px;
  background: var(--color-primary);
  border-radius: var(--radius-full);
  transition: all var(--transition-fast);
}

/* ==========================================
   MAIN CONTENT
   ========================================== */
main {
  position: relative;
  z-index: 1;
  padding-top: 64px;
  min-height: calc(100vh - 64px);
}

/* ==========================================
   HERO - Simple Home Page
   ========================================== */
.hero-simple {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 50vh;
  text-align: center;
  padding: var(--space-3xl) var(--space-xl) var(--space-xl);
}

.hero-title {
  font-size: 4rem;
  font-weight: 700;
  color: var(--color-primary);
  letter-spacing: 2px;
  margin-bottom: var(--space-md);
}

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

.hero-logo {
  height: 200px;
  width: auto;
  margin-bottom: var(--space-md);
}

.hero-tagline {
  font-size: 1.25rem;
  color: var(--color-text-tertiary);
  font-weight: 400;
  margin-bottom: var(--space-2xl);
  max-width: 500px;
}

.hero-buttons {
  display: flex;
  gap: var(--space-md);
  flex-wrap: wrap;
  justify-content: center;
}

/* ==========================================
   BUTTONS
   ========================================== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  font-size: 0.95rem;
  font-weight: 500;
  border-radius: var(--radius-md);
  border: none;
  cursor: pointer;
  transition: all var(--transition-base);
  text-decoration: none;
}

.btn:hover {
  text-decoration: none;
  transform: translateY(-1px);
}

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

.btn-primary:hover {
  background: var(--color-accent-hover);
  color: white;
  box-shadow: var(--shadow-md);
}

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

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

.btn-ghost {
  background: transparent;
  color: var(--color-text-secondary);
}

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

/* Home hero buttons */
.btn-hero {
  color: #ffffff;
  border: 1px solid transparent;
}

.btn-hero:hover {
  color: #ffffff;
  box-shadow: var(--shadow-md);
}

.btn-architecture {
  background: #4f6fa3;
}

.btn-architecture:hover {
  background: #3f5f93;
}

.btn-demos {
  background: #3f7f7a;
}

.btn-demos:hover {
  background: #356a66;
}

.btn-videos {
  background: #9a6a3a;
}

.btn-videos:hover {
  background: #875d33;
}

.btn-paper {
  background: #8a4a5a;
}

.btn-paper:hover {
  background: #77404f;
}

/* ==========================================
   SECTIONS
   ========================================== */
.section {
  padding: var(--space-3xl) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-2xl);
}

.section-title {
  font-size: 1.75rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  color: var(--color-primary);
}

.section-subtitle {
  font-size: 1rem;
  color: var(--color-text-tertiary);
  max-width: 600px;
  margin: 0 auto;
}

.section-divider {
  height: 1px;
  background: var(--color-border);
  margin: var(--space-2xl) 0;
  border: none;
}

/* ==========================================
   CARDS
   ========================================== */
.card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  padding: var(--space-xl);
  transition: all var(--transition-base);
}

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

.card-title {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: var(--space-sm);
  color: var(--color-primary);
}

.card-description {
  color: var(--color-text-secondary);
  font-size: 0.95rem;
  line-height: 1.6;
}

/* ==========================================
   GRID LAYOUTS
   ========================================== */
.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--space-xl);
}

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--space-xl);
}

.grid-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--space-lg);
}

/* ==========================================
   FOOTER
   ========================================== */
.footer {
  text-align: center;
  padding: var(--space-xl) 0;
  border-top: 1px solid var(--color-border);
  background: var(--color-bg-secondary);
}

.footer-content {
  display: flex;
  justify-content: center;
  align-items: center;
  flex-wrap: wrap;
  gap: var(--space-lg);
  flex-direction: column;
}

.footer-text {
  color: var(--color-text-tertiary);
  font-size: 0.875rem;
  margin: 0;
}

.footer-links {
  display: flex;
  gap: var(--space-lg);
}

.footer-links a {
  color: var(--color-text-tertiary);
  font-size: 0.875rem;
}

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

.footer-logos {
  display: flex;
  align-items: center;
  gap: var(--space-md);
}

.footer-logo-link {
  display: inline-block;
  transition: opacity var(--transition-fast);
}

.footer-logo-link:hover {
  opacity: 0.8;
}

.footer-logo {
  height: 32px;
  width: auto;
  border-radius: var(--radius-sm);
}

.footer-logo.footer-logo-lg {
  height: 60px;
}

/* ==========================================
   CODE BLOCK
   ========================================== */
.code-block {
  background: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.6;
  color: var(--color-text-primary);
}

/* ==========================================
   FIGURE & VIDEO
   ========================================== */
.figure {
  margin: var(--space-xl) 0;
  text-align: center;
}

.figure img {
  max-width: 100%;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
}

.figure-caption {
  margin-top: var(--space-sm);
  font-size: 0.875rem;
  color: var(--color-text-tertiary);
}

.video-container {
  margin: var(--space-xl) 0;
  text-align: center;
}

.video-container video {
  width: 100%;
  max-width: 100%;
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-md);
}

/* ==========================================
   UTILITY CLASSES
   ========================================== */
.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

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

.mt-sm { margin-top: var(--space-sm); }
.mt-md { margin-top: var(--space-md); }
.mt-lg { margin-top: var(--space-lg); }
.mt-xl { margin-top: var(--space-xl); }

.mb-sm { margin-bottom: var(--space-sm); }
.mb-md { margin-bottom: var(--space-md); }
.mb-lg { margin-bottom: var(--space-lg); }
.mb-xl { margin-bottom: var(--space-xl); }

/* ==========================================
   SCROLL TO TOP
   ========================================== */
.scroll-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 44px;
  height: 44px;
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  cursor: pointer;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
  z-index: 999;
  display: flex;
  align-items: center;
  justify-content: center;
}

.scroll-top:hover {
  background: var(--color-bg-secondary);
  color: var(--color-accent);
}

.scroll-top.visible {
  opacity: 1;
  visibility: visible;
}

/* ==========================================
   ANIMATIONS
   ========================================== */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

.animate-fade-in {
  animation: fadeIn 0.5s ease forwards;
}

.animate-fade-in-up {
  animation: fadeInUp 0.5s ease forwards;
}

/* ==========================================
   CITATION SECTION (Home Page)
   ========================================== */
.citation-section {
  padding: var(--space-xl) 0;
  margin-top: var(--space-2xl);
}

.citation-title {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--color-text-tertiary);
  text-align: center;
  margin-bottom: var(--space-md);
}

.citation-card {
  max-width: 700px;
  margin: 0 auto;
  background: var(--color-bg-secondary);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  overflow: hidden;
}

.citation-tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg-tertiary);
}

.citation-tab {
  flex: 1;
  padding: 10px 12px;
  background: transparent;
  border: none;
  border-right: 1px solid var(--color-border);
  font-size: 0.8rem;
  font-weight: 500;
  color: var(--color-text-secondary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.citation-tab:last-child {
  border-right: none;
}

.citation-tab:hover {
  color: var(--color-accent);
  background: var(--color-bg-secondary);
}

.citation-tab.active {
  color: var(--color-accent);
  background: var(--color-bg-card);
  border-bottom: 2px solid var(--color-accent);
  font-weight: 600;
}

.citation-content {
  padding: var(--space-md);
  position: relative;
}

.citation-text {
  display: none;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  line-height: 1.5;
  color: var(--color-text-secondary);
  white-space: pre-wrap;
  word-break: break-word;
  margin-bottom: var(--space-sm);
}

.citation-text.active {
  display: block;
}

.citation-copy-btn {
  font-size: 0.7rem;
  padding: 4px 10px;
}

/* ==========================================
   RESPONSIVE
   ========================================== */
@media (max-width: 1024px) {
  .grid-3 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: var(--color-bg-card);
    flex-direction: column;
    padding: var(--space-lg);
    gap: var(--space-xs);
    border-bottom: 1px solid var(--color-border);
    transform: translateY(-100%);
    opacity: 0;
    visibility: hidden;
    transition: all var(--transition-base);
    box-shadow: var(--shadow-lg);
  }

  .nav-menu.active {
    transform: translateY(0);
    opacity: 1;
    visibility: visible;
  }

  .nav-submenu {
    position: static;
    min-width: auto;
    border: none;
    box-shadow: none;
    background: var(--color-bg-secondary);
    padding: var(--space-sm) 0;
    margin: var(--space-xs) 0 0 var(--space-md);
    opacity: 1;
    visibility: visible;
    transform: none;
    display: none;
    border-radius: var(--radius-sm);
  }

  .nav-dropdown.open .nav-submenu {
    display: block;
  }

  .nav-toggle {
    display: flex;
  }

  .nav-toggle.active .bar:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }

  .nav-toggle.active .bar:nth-child(2) {
    opacity: 0;
  }

  .nav-toggle.active .bar:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
  }

  .hero-title {
    font-size: 2.5rem;
  }

  .hero-tagline {
    font-size: 1rem;
  }

  .hero-buttons {
    flex-direction: column;
    width: 100%;
    max-width: 280px;
  }

  .btn {
    width: 100%;
    justify-content: center;
  }

  .grid-2,
  .grid-3 {
    grid-template-columns: 1fr;
  }

  .section {
    padding: var(--space-2xl) 0;
  }
}

@media (max-width: 480px) {
  .container {
    padding: 0 var(--space-md);
  }

  .nav-container {
    padding: 0 var(--space-md);
  }

  .hero-title {
    font-size: 2rem;
    letter-spacing: 1px;
  }
}