/* ============================================
   CSS Custom Properties & Design System
   ============================================ */
:root {
  /* Colors - Dark Theme with Tech Gradients */
  --color-bg: #0a0e27;
  --color-bg-secondary: #111831;
  --color-surface: rgba(255, 255, 255, 0.05);
  --color-surface-hover: rgba(255, 255, 255, 0.08);
  
  --color-primary: #6366f1;
  --color-primary-light: #818cf8;
  --color-secondary: #8b5cf6;
  --color-accent: #06b6d4;
  
  --color-text-primary: #f8fafc;
  --color-text-secondary: #cbd5e1;
  --color-text-muted: #94a3b8;
  
  --gradient-primary: linear-gradient(135deg, #6366f1 0%, #8b5cf6 100%);
  --gradient-accent: linear-gradient(135deg, #06b6d4 0%, #3b82f6 100%);
  --gradient-bg: linear-gradient(180deg, #0a0e27 0%, #111831 100%);
  
  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-2xl: 4rem;
  
  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Courier New', monospace;
  
  --text-xs: 0.75rem;
  --text-sm: 0.875rem;
  --text-base: 1rem;
  --text-lg: 1.125rem;
  --text-xl: 1.25rem;
  --text-2xl: 1.5rem;
  --text-3xl: 2rem;
  --text-4xl: 2.5rem;
  --text-5xl: clamp(2.5rem, 5vw, 3.5rem);
  
  /* Borders & Shadows */
  --radius-sm: 0.5rem;
  --radius-md: 0.75rem;
  --radius-lg: 1rem;
  
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 6px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 10px 25px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 20px rgba(99, 102, 241, 0.3);
  
  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  font-family: var(--font-sans);
  font-size: var(--text-base);
  line-height: 1.6;
  color: var(--color-text-primary);
  background: var(--gradient-bg);
  background-attachment: fixed;
  overflow-x: hidden;
}

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

/* ============================================
   Typography
   ============================================ */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--spacing-sm);
}

h1 { font-size: var(--text-5xl); }
h2 { font-size: var(--text-4xl); }
h3 { font-size: var(--text-3xl); }
h4 { font-size: var(--text-2xl); }

p {
  margin-bottom: var(--spacing-md);
  color: var(--color-text-secondary);
}

a {
  color: var(--color-primary-light);
  text-decoration: none;
  transition: color var(--transition-base);
}

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

code {
  font-family: var(--font-mono);
  background: var(--color-surface);
  padding: 0.2em 0.4em;
  border-radius: 0.25rem;
  font-size: 0.9em;
}

/* ============================================
   Header & Navigation
   ============================================ */
header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  background: rgba(10, 14, 39, 0.8);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  transition: all var(--transition-base);
}

header.scrolled {
  box-shadow: var(--shadow-lg);
}

nav {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-md) var(--spacing-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: var(--text-xl);
  font-weight: 700;
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav-links {
  display: flex;
  gap: var(--spacing-lg);
  list-style: none;
}

.nav-links a {
  color: var(--color-text-secondary);
  font-weight: 500;
  position: relative;
  padding: var(--spacing-xs) 0;
  transition: color var(--transition-base);
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--gradient-primary);
  transition: width var(--transition-base);
}

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

.nav-links a:hover::after,
.nav-links a.active::after {
  width: 100%;
}

.menu-toggle {
  display: none;
  flex-direction: column;
  gap: 4px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-xs);
}

.menu-toggle span {
  width: 24px;
  height: 2px;
  background: var(--color-text-primary);
  transition: all var(--transition-base);
}

/* ============================================
   Hero Section
   ============================================ */
#hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--spacing-2xl) var(--spacing-lg);
  position: relative;
  overflow: hidden;
}

#hero::before {
  content: '';
  position: absolute;
  top: -50%;
  right: -50%;
  width: 100%;
  height: 100%;
  background: radial-gradient(circle, rgba(99, 102, 241, 0.1) 0%, transparent 70%);
  animation: pulse 8s ease-in-out infinite;
}

@keyframes pulse {
  0%, 100% { transform: scale(1) translateY(0); opacity: 0.5; }
  50% { transform: scale(1.1) translateY(-20px); opacity: 0.8; }
}

.hero-content {
  position: relative;
  z-index: 1;
  max-width: 800px;
}

.hero-subtitle {
  font-size: var(--text-lg);
  color: var(--color-accent);
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  text-transform: uppercase;
  letter-spacing: 2px;
}

.hero-title {
  font-size: var(--text-5xl);
  margin-bottom: var(--spacing-md);
  background: var(--gradient-primary);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero-description {
  font-size: var(--text-xl);
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-xl);
  line-height: 1.8;
}

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

.btn {
  padding: var(--spacing-md) var(--spacing-lg);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: var(--text-base);
  cursor: pointer;
  transition: all var(--transition-base);
  border: none;
  text-decoration: none;
  display: inline-block;
}

.btn-primary {
  background: var(--gradient-primary);
  color: white;
  box-shadow: var(--shadow-glow);
}

.btn-primary:hover {
  transform: translateY(-2px);
  box-shadow: 0 0 30px rgba(99, 102, 241, 0.5);
}

.btn-secondary {
  background: var(--color-surface);
  color: var(--color-text-primary);
  border: 1px solid rgba(255, 255, 255, 0.1);
}

.btn-secondary:hover {
  background: var(--color-surface-hover);
  border-color: rgba(255, 255, 255, 0.2);
}

/* ============================================
   Section Base Styles
   ============================================ */
section {
  padding: var(--spacing-2xl) var(--spacing-lg);
  max-width: 1200px;
  margin: 0 auto;
}

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

.section-title {
  position: relative;
  display: inline-block;
  margin-bottom: var(--spacing-md);
}

.section-title::after {
  content: '';
  position: absolute;
  bottom: -10px;
  left: 50%;
  transform: translateX(-50%);
  width: 60px;
  height: 4px;
  background: var(--gradient-primary);
  border-radius: 2px;
}

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

/* ============================================
   About Section
   ============================================ */
.about-content {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-xl);
  align-items: center;
}

.about-text {
  font-size: var(--text-lg);
  line-height: 1.8;
}

.focus-areas {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
}

.focus-card {
  background: var(--color-surface);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  transition: all var(--transition-base);
}

.focus-card:hover {
  transform: translateY(-4px);
  background: var(--color-surface-hover);
  border-color: rgba(99, 102, 241, 0.3);
  box-shadow: var(--shadow-glow);
}

.focus-card h4 {
  color: var(--color-primary-light);
  margin-bottom: var(--spacing-sm);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.focus-card h4::before {
  content: '▹';
  color: var(--color-accent);
  font-size: var(--text-xl);
}

.focus-card p {
  font-size: var(--text-sm);
  margin: 0;
}

/* ============================================
   Experience Section
   ============================================ */
.timeline {
  position: relative;
  padding-left: var(--spacing-xl);
}

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

.timeline-item {
  position: relative;
  margin-bottom: var(--spacing-xl);
  padding-left: var(--spacing-xl);
}

.timeline-item::before {
  content: '';
  position: absolute;
  left: -36px;
  top: 6px;
  width: 12px;
  height: 12px;
  border-radius: 50%;
  background: var(--color-primary);
  box-shadow: 0 0 0 4px var(--color-bg), var(--shadow-glow);
}

.timeline-header {
  margin-bottom: var(--spacing-md);
}

.timeline-period {
  color: var(--color-accent);
  font-size: var(--text-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.timeline-title {
  font-size: var(--text-2xl);
  margin: var(--spacing-xs) 0;
}

.timeline-company {
  color: var(--color-text-muted);
  font-size: var(--text-base);
}

.timeline-content {
  background: var(--color-surface);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  transition: all var(--transition-base);
}

.timeline-content:hover {
  background: var(--color-surface-hover);
  border-color: rgba(99, 102, 241, 0.2);
}

.timeline-content ul {
  list-style: none;
  margin-top: var(--spacing-md);
}

.timeline-content li {
  position: relative;
  padding-left: var(--spacing-md);
  margin-bottom: var(--spacing-sm);
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  line-height: 1.7;
}

.timeline-content li::before {
  content: '▸';
  position: absolute;
  left: 0;
  color: var(--color-accent);
}

.tech-stack {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-xs);
  margin-top: var(--spacing-md);
  padding-top: var(--spacing-md);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.tech-tag {
  background: rgba(99, 102, 241, 0.1);
  color: var(--color-primary-light);
  padding: 0.25rem 0.75rem;
  border-radius: var(--radius-sm);
  font-size: var(--text-xs);
  font-family: var(--font-mono);
  border: 1px solid rgba(99, 102, 241, 0.2);
}

/* ============================================
   Skills Section
   ============================================ */
.skills-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-lg);
}

.skill-category {
  background: var(--color-surface);
  backdrop-filter: blur(10px);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg);
  padding: var(--spacing-lg);
  transition: all var(--transition-base);
}

.skill-category:hover {
  transform: translateY(-4px);
  background: var(--color-surface-hover);
  box-shadow: var(--shadow-glow);
}

.skill-category h3 {
  color: var(--color-primary-light);
  margin-bottom: var(--spacing-md);
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-size: var(--text-xl);
}

.skill-category h3::before {
  content: '◆';
  color: var(--color-accent);
}

.skill-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-sm);
}

.skill-tag {
  background: rgba(6, 182, 212, 0.1);
  color: var(--color-accent);
  padding: 0.5rem 1rem;
  border-radius: var(--radius-md);
  font-size: var(--text-sm);
  font-weight: 500;
  border: 1px solid rgba(6, 182, 212, 0.2);
  transition: all var(--transition-fast);
}

.skill-tag:hover {
  background: rgba(6, 182, 212, 0.2);
  transform: scale(1.05);
}

/* ============================================
   Education Section
   ============================================ */
.education-card {
  background: var(--color-surface);
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  max-width: 700px;
  margin: 0 auto;
}

.education-card h3 {
  color: var(--color-primary-light);
  font-size: var(--text-2xl);
  margin-bottom: var(--spacing-sm);
}

.education-details {
  color: var(--color-text-secondary);
  font-size: var(--text-base);
}

.education-year {
  color: var(--color-accent);
  font-weight: 600;
  margin-top: var(--spacing-sm);
}

/* ============================================
   Contact Section
   ============================================ */
#contact {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: var(--spacing-2xl);
  margin: var(--spacing-2xl) var(--spacing-lg);
  max-width: 1200px;
  margin-left: auto;
  margin-right: auto;
}

.contact-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
  margin-top: var(--spacing-xl);
}

.contact-item {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  background: rgba(255, 255, 255, 0.03);
  border-radius: var(--radius-md);
  transition: all var(--transition-base);
}

.contact-item:hover {
  background: rgba(255, 255, 255, 0.06);
  transform: translateX(4px);
}

.contact-icon {
  font-size: var(--text-2xl);
  color: var(--color-accent);
}

.contact-info h4 {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 0.25rem;
}

.contact-info a,
.contact-info p {
  color: var(--color-text-primary);
  font-size: var(--text-base);
  margin: 0;
}

/* ============================================
   Footer
   ============================================ */
footer {
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-lg);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  color: var(--color-text-muted);
}

/* ============================================
   Animations & Utilities
   ============================================ */
.fade-in {
  opacity: 0;
  transform: translateY(30px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.fade-in.visible {
  opacity: 1;
  transform: translateY(0);
}

.stagger-1 { transition-delay: 0.1s; }
.stagger-2 { transition-delay: 0.2s; }
.stagger-3 { transition-delay: 0.3s; }

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 768px) {
  :root {
    --spacing-xl: 2rem;
    --spacing-2xl: 3rem;
  }
  
  nav {
    padding: var(--spacing-sm) var(--spacing-md);
  }
  
  .nav-links {
    position: fixed;
    top: 64px;
    left: 0;
    right: 0;
    background: rgba(10, 14, 39, 0.98);
    backdrop-filter: blur(12px);
    flex-direction: column;
    padding: var(--spacing-lg);
    transform: translateY(-100%);
    opacity: 0;
    transition: all var(--transition-base);
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
  }
  
  .nav-links.active {
    transform: translateY(0);
    opacity: 1;
  }
  
  .menu-toggle {
    display: flex;
  }
  
  .menu-toggle.active span:nth-child(1) {
    transform: rotate(45deg) translate(5px, 5px);
  }
  
  .menu-toggle.active span:nth-child(2) {
    opacity: 0;
  }
  
  .menu-toggle.active span:nth-child(3) {
    transform: rotate(-45deg) translate(5px, -5px);
  }
  
  #hero {
    min-height: calc(100vh - 64px);
    padding: var(--spacing-xl) var(--spacing-md);
  }
  
  .hero-title {
    font-size: clamp(2rem, 8vw, 3rem);
  }
  
  .hero-description {
    font-size: var(--text-base);
  }
  
  .hero-cta {
    flex-direction: column;
  }
  
  .btn {
    width: 100%;
    text-align: center;
  }
  
  section {
    padding: var(--spacing-xl) var(--spacing-md);
  }
  
  .timeline {
    padding-left: var(--spacing-md);
  }
  
  .timeline-item {
    padding-left: var(--spacing-lg);
  }
  
  .timeline-item::before {
    left: -24px;
  }
  
  .focus-areas,
  .skills-grid {
    grid-template-columns: 1fr;
  }
  
  .contact-grid {
    grid-template-columns: 1fr;
  }
}