/* ==========================================================================
   Shri Kant, PhD - Academic & Personal Website Design System
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=Outfit:wght@400;500;600;700;800&family=Fira+Code:wght@400;500&display=swap');

:root {
  /* Color Palette - Dark Mode Default */
  --bg-primary: #0f172a;
  --bg-secondary: #1e293b;
  --bg-card: rgba(30, 41, 59, 0.7);
  --bg-card-hover: rgba(51, 65, 85, 0.8);
  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  
  --accent-primary: #38bdf8;
  --accent-secondary: #818cf8;
  --accent-teal: #2dd4bf;
  --accent-rose: #fb7185;
  --accent-gradient: linear-gradient(135deg, #38bdf8 0%, #818cf8 100%);
  --accent-gradient-hover: linear-gradient(135deg, #0284c7 0%, #6366f1 100%);
  
  --border-color: rgba(255, 255, 255, 0.1);
  --border-color-hover: rgba(56, 189, 248, 0.4);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.3);
  --shadow-lg: 0 16px 32px rgba(0, 0, 0, 0.4);

  --font-heading: 'Outfit', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-body: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
  --font-code: 'Fira Code', monospace;

  --nav-height: 70px;
  --radius-sm: 8px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
}

[data-theme="light"] {
  --bg-primary: #f8fafc;
  --bg-secondary: #f1f5f9;
  --bg-card: rgba(255, 255, 255, 0.85);
  --bg-card-hover: #ffffff;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #64748b;
  
  --accent-primary: #0284c7;
  --accent-secondary: #4f46e5;
  --accent-teal: #0d9488;
  --accent-rose: #e11d48;
  --accent-gradient: linear-gradient(135deg, #0284c7 0%, #4f46e5 100%);
  --accent-gradient-hover: linear-gradient(135deg, #0369a1 0%, #4338ca 100%);
  
  --border-color: rgba(0, 0, 0, 0.08);
  --border-color-hover: rgba(2, 132, 199, 0.4);
  --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.05);
  --shadow-md: 0 8px 24px rgba(15, 23, 42, 0.08);
  --shadow-lg: 0 16px 32px rgba(15, 23, 42, 0.12);
}

/* ==========================================================================
   Base & Typography
   ========================================================================== */

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

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

h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-heading);
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-primary);
}

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

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

ul {
  list-style: none;
}

/* Layout Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 6rem 0;
  position: relative;
}

.section-title {
  font-size: 2.25rem;
  margin-bottom: 0.75rem;
  position: relative;
  display: inline-block;
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -6px;
  left: 0;
  width: 50px;
  height: 4px;
  background: var(--accent-gradient);
  border-radius: 2px;
}

.section-subtitle {
  color: var(--text-secondary);
  font-size: 1.1rem;
  margin-bottom: 3rem;
  max-width: 700px;
}

/* ==========================================================================
   Navigation Bar
   ========================================================================== */

.navbar {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: var(--nav-height);
  background: rgba(15, 23, 42, 0.85);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  z-index: 1000;
  border-bottom: 1px solid var(--border-color);
  transition: background var(--transition-normal), border var(--transition-normal);
}

[data-theme="light"] .navbar {
  background: rgba(248, 250, 252, 0.85);
}

.navbar .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: 100%;
}

.nav-brand {
  font-family: var(--font-heading);
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.nav-brand span {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

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

.nav-link {
  color: var(--text-secondary);
  font-weight: 500;
  font-size: 0.95rem;
  transition: color var(--transition-fast);
  position: relative;
  padding: 0.25rem 0;
}

.nav-link:hover, .nav-link.active {
  color: var(--text-primary);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  height: 2px;
  background: var(--accent-gradient);
  border-radius: 1px;
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 1rem;
}

/* Theme Toggle Switch */
.theme-toggle {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  width: 40px;
  height: 40px;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  border-color: var(--accent-primary);
  transform: scale(1.05);
}

.hamburger {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  font-size: 1.5rem;
  cursor: pointer;
}

/* ==========================================================================
   Hero Section
   ========================================================================== */

.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  padding-top: calc(var(--nav-height) + 2rem);
  background: radial-gradient(circle at 10% 20%, rgba(56, 189, 248, 0.08) 0%, transparent 40%),
              radial-gradient(circle at 90% 80%, rgba(129, 140, 248, 0.08) 0%, transparent 40%);
}

.hero-grid {
  display: grid;
  grid-template-columns: 1.2fr 0.8fr;
  gap: 4rem;
  align-items: center;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 1rem;
  background: rgba(56, 189, 248, 0.1);
  border: 1px solid rgba(56, 189, 248, 0.2);
  border-radius: 50px;
  color: var(--accent-primary);
  font-size: 0.875rem;
  font-weight: 600;
  margin-bottom: 1.5rem;
}

.hero-title {
  font-size: 3.5rem;
  font-weight: 800;
  margin-bottom: 1rem;
  letter-spacing: -0.02em;
}

.hero-title .gradient-text {
  background: var(--accent-gradient);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-subtitle {
  font-size: 1.35rem;
  color: var(--text-secondary);
  margin-bottom: 1.5rem;
  font-weight: 500;
}

.hero-description {
  color: var(--text-secondary);
  font-size: 1.05rem;
  margin-bottom: 2rem;
  max-width: 620px;
}

.hero-cta {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 2.5rem;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.8rem 1.75rem;
  border-radius: var(--radius-sm);
  font-weight: 600;
  font-size: 0.95rem;
  cursor: pointer;
  transition: all var(--transition-fast);
  border: none;
}

.btn-primary {
  background: var(--accent-gradient);
  color: #ffffff;
  box-shadow: 0 4px 14px rgba(56, 189, 248, 0.3);
}

.btn-primary:hover {
  background: var(--accent-gradient-hover);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(56, 189, 248, 0.4);
  color: #ffffff;
}

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

.btn-outline:hover {
  border-color: var(--accent-primary);
  color: var(--accent-primary);
  background: rgba(56, 189, 248, 0.05);
  transform: translateY(-2px);
}

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

.social-icon {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  transition: all var(--transition-fast);
}

.social-icon:hover {
  color: var(--accent-primary);
  border-color: var(--accent-primary);
  transform: translateY(-3px);
}

/* Avatar Card */
.avatar-card {
  position: relative;
  border-radius: var(--radius-lg);
  padding: 1rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  backdrop-filter: blur(10px);
  box-shadow: var(--shadow-lg);
  text-align: center;
}

.avatar-img-wrapper {
  width: 220px;
  height: 220px;
  margin: 0 auto 1.5rem;
  border-radius: 50%;
  padding: 6px;
  background: var(--accent-gradient);
  position: relative;
  box-shadow: 0 10px 30px rgba(56, 189, 248, 0.2);
}

.avatar-img {
  width: 100%;
  height: 100%;
  border-radius: 50%;
  object-fit: cover;
  background: var(--bg-secondary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 4.5rem;
  color: var(--accent-primary);
}

.avatar-info h3 {
  font-size: 1.4rem;
  margin-bottom: 0.25rem;
}

.avatar-info p {
  color: var(--text-secondary);
  font-size: 0.9rem;
}

.avatar-stats {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 0.5rem;
  margin-top: 1.5rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
}

.stat-item h4 {
  font-size: 1.5rem;
  color: var(--accent-primary);
}

.stat-item p {
  font-size: 0.75rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

/* ==========================================================================
   About & Research Focus Cards
   ========================================================================== */

.grid-3 {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 1.5rem;
}

.grid-2 {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.75rem;
  transition: all var(--transition-normal);
  backdrop-filter: blur(8px);
}

.card:hover {
  border-color: var(--border-color-hover);
  transform: translateY(-4px);
  box-shadow: var(--shadow-md);
}

.card-icon {
  width: 48px;
  height: 48px;
  border-radius: var(--radius-sm);
  background: rgba(56, 189, 248, 0.1);
  color: var(--accent-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.4rem;
  margin-bottom: 1.25rem;
}

.card h3 {
  font-size: 1.2rem;
  margin-bottom: 0.75rem;
}

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

/* ==========================================================================
   Software Packages Section
   ========================================================================== */

.software-card {
  display: grid;
  grid-template-columns: 1fr 2fr;
  gap: 2rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 2.5rem;
  margin-bottom: 2rem;
  backdrop-filter: blur(12px);
}

.software-header {
  border-right: 1px solid var(--border-color);
  padding-right: 2rem;
}

.software-title {
  font-size: 2rem;
  margin-bottom: 0.5rem;
}

.software-badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  background: rgba(45, 212, 191, 0.1);
  color: var(--accent-teal);
  border-radius: 50px;
  font-size: 0.8rem;
  font-weight: 600;
  margin-bottom: 1rem;
}

.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-top: 1rem;
}

.tag {
  padding: 0.25rem 0.6rem;
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-size: 0.8rem;
  color: var(--text-secondary);
  font-family: var(--font-code);
}

.software-features {
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.feature-list {
  margin: 1rem 0;
}

.feature-item {
  display: flex;
  align-items: flex-start;
  gap: 0.75rem;
  margin-bottom: 0.75rem;
  color: var(--text-secondary);
}

.feature-item i {
  color: var(--accent-primary);
  margin-top: 0.25rem;
}

/* ==========================================================================
   Publications Filter & Cards
   ========================================================================== */

.pub-filter {
  display: flex;
  gap: 0.75rem;
  margin-bottom: 2rem;
  flex-wrap: wrap;
}

.filter-btn {
  padding: 0.5rem 1.25rem;
  border-radius: 50px;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
}

.filter-btn:hover, .filter-btn.active {
  background: var(--accent-gradient);
  color: #ffffff;
  border-color: transparent;
}

.publication-item {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.75rem;
  margin-bottom: 1.25rem;
  transition: all var(--transition-normal);
  position: relative;
}

.publication-item:hover {
  border-color: var(--border-color-hover);
  transform: translateX(4px);
}

.pub-meta {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.5rem;
}

.pub-journal {
  font-weight: 600;
  color: var(--accent-primary);
  font-size: 0.9rem;
}

.pub-year {
  padding: 0.15rem 0.5rem;
  background: var(--bg-secondary);
  border-radius: 4px;
  font-size: 0.8rem;
  color: var(--text-muted);
}

.pub-title {
  font-size: 1.15rem;
  margin-bottom: 0.5rem;
}

.pub-authors {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
}

.pub-authors strong {
  color: var(--text-primary);
  text-decoration: underline;
  text-decoration-color: var(--accent-primary);
}

.pub-links {
  display: flex;
  gap: 0.75rem;
  margin-top: 1rem;
}

.pub-link {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-size: 0.85rem;
  font-weight: 600;
  padding: 0.3rem 0.75rem;
  border-radius: 4px;
  background: rgba(56, 189, 248, 0.1);
  color: var(--accent-primary);
}

.pub-link:hover {
  background: var(--accent-primary);
  color: #ffffff;
}

/* ==========================================================================
   Experience & Education Timeline
   ========================================================================== */

.timeline {
  position: relative;
  padding-left: 2rem;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 0;
  top: 10px;
  bottom: 10px;
  width: 2px;
  background: var(--border-color);
}

.timeline-item {
  position: relative;
  margin-bottom: 2.5rem;
}

.timeline-dot {
  position: absolute;
  left: -2rem;
  top: 5px;
  transform: translateX(-50%);
  width: 14px;
  height: 14px;
  border-radius: 50%;
  background: var(--accent-primary);
  border: 3px solid var(--bg-primary);
  box-shadow: 0 0 10px var(--accent-primary);
}

.timeline-content {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.5rem;
}

.timeline-date {
  font-size: 0.85rem;
  color: var(--accent-primary);
  font-weight: 600;
  margin-bottom: 0.25rem;
}

.timeline-title {
  font-size: 1.2rem;
  margin-bottom: 0.25rem;
}

.timeline-subtitle {
  color: var(--text-secondary);
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
}

/* ==========================================================================
   Skills Grid & Badge Tags
   ========================================================================== */

.skills-category {
  margin-bottom: 2rem;
}

.skills-category h3 {
  font-size: 1.1rem;
  margin-bottom: 1rem;
  color: var(--text-primary);
}

.skill-badges {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.skill-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.5rem 1rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 50px;
  font-size: 0.9rem;
  color: var(--text-secondary);
  transition: all var(--transition-fast);
}

.skill-badge:hover {
  border-color: var(--accent-primary);
  color: var(--text-primary);
  transform: translateY(-2px);
}

/* ==========================================================================
   Contact Section
   ========================================================================== */

.contact-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 3rem;
}

.contact-info-card {
  display: flex;
  align-items: center;
  gap: 1.25rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.25rem 1.5rem;
  margin-bottom: 1rem;
}

.contact-icon {
  width: 46px;
  height: 46px;
  border-radius: 50%;
  background: rgba(56, 189, 248, 0.1);
  color: var(--accent-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.25rem;
}

/* Footer */
footer {
  padding: 3rem 0;
  border-top: 1px solid var(--border-color);
  background: var(--bg-secondary);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
}

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

@media (max-width: 992px) {
  .hero-grid {
    grid-template-columns: 1fr;
    gap: 3rem;
    text-align: center;
  }

  .hero-description {
    margin-left: auto;
    margin-right: auto;
  }

  .hero-cta {
    justify-content: center;
  }

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

  .software-card {
    grid-template-columns: 1fr;
  }

  .software-header {
    border-right: none;
    border-bottom: 1px solid var(--border-color);
    padding-right: 0;
    padding-bottom: 1.5rem;
  }

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

@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    top: var(--nav-height);
    right: -100%;
    width: 250px;
    height: calc(100vh - var(--nav-height));
    background: var(--bg-secondary);
    flex-direction: column;
    align-items: flex-start;
    padding: 2rem;
    transition: right var(--transition-normal);
    box-shadow: var(--shadow-lg);
  }

  .nav-menu.active {
    right: 0;
  }

  .hamburger {
    display: block;
  }

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

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