/* ============================================
   CSS Variables for Light and Dark Themes
   ============================================ */
:root {
  /* Light Theme Colors */
  --bg-primary: #ffffff;
  --bg-secondary: #f8f9fa;
  --bg-tertiary: #e9ecef;
  --text-primary: #212529;
  --text-secondary: #6c757d;
  --text-muted: #adb5bd;
  --accent-primary: #0066cc;
  --accent-secondary: #0052a3;
  --accent-hover: #004080;
  --border-color: #dee2e6;
  --shadow-light: rgba(0, 0, 0, 0.05);
  --shadow-medium: rgba(0, 0, 0, 0.1);
  --shadow-dark: rgba(0, 0, 0, 0.15);
  --success: #28a745;
  --warning: #ffc107;
  --danger: #dc3545;
  --info: #17a2b8;
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  --spacing-3xl: 4rem;
  
  /* Typography */
  --font-primary: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  --font-secondary: Georgia, 'Times New Roman', Times, serif;
  --font-mono: 'Courier New', Courier, monospace;
  --font-size-base: 16px;
  --line-height-base: 1.6;
  
  /* Border Radius */
  --radius-sm: 4px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;
  --radius-full: 9999px;
  
  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-base: 0.3s ease;
  --transition-slow: 0.5s ease;
  
  /* Layout */
  --container-max-width: 1200px;
  --header-height: 70px;
}

/* Dark Theme */
[data-theme="dark"] {
  --bg-primary: #1a1a1a;
  --bg-secondary: #2d2d2d;
  --bg-tertiary: #3a3a3a;
  --text-primary: #f8f9fa;
  --text-secondary: #adb5bd;
  --text-muted: #6c757d;
  --accent-primary: #4da6ff;
  --accent-secondary: #3399ff;
  --accent-hover: #66b3ff;
  --border-color: #495057;
  --shadow-light: rgba(255, 255, 255, 0.05);
  --shadow-medium: rgba(255, 255, 255, 0.1);
  --shadow-dark: rgba(255, 255, 255, 0.15);
}

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

html {
  scroll-behavior: smooth;
  font-size: var(--font-size-base);
}

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

/* Preloader */
.preloader {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 100%;
  background-color: var(--bg-primary);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 9999;
  transition: opacity var(--transition-slow), visibility var(--transition-slow);
}

.preloader.hidden {
  opacity: 0;
  visibility: hidden;
}

.preloader-spinner {
  width: 50px;
  height: 50px;
  border: 4px solid var(--border-color);
  border-top-color: var(--accent-primary);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to {
    transform: rotate(360deg);
  }
}

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

h1 {
  font-size: 2.5rem;
}

h2 {
  font-size: 2rem;
}

h3 {
  font-size: 1.75rem;
}

h4 {
  font-size: 1.5rem;
}

h5 {
  font-size: 1.25rem;
}

h6 {
  font-size: 1rem;
}

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

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

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

/* ============================================
   Header and Navigation
   ============================================ */
.site-header {
  background-color: var(--bg-primary);
  box-shadow: 0 2px 8px var(--shadow-light);
  position: sticky;
  top: 0;
  z-index: 1000;
  transition: background-color var(--transition-base), box-shadow var(--transition-base);
}

.site-header.scrolled {
  box-shadow: 0 4px 12px var(--shadow-medium);
}

.header-container {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
  height: var(--header-height);
}

.logo {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--text-primary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

.nav-menu {
  display: flex;
  list-style: none;
  gap: var(--spacing-xl);
  align-items: center;
}

.nav-menu a {
  color: var(--text-primary);
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-md);
  transition: background-color var(--transition-fast), color var(--transition-fast);
}

.nav-menu a:hover,
.nav-menu a.active {
  background-color: var(--bg-secondary);
  color: var(--accent-primary);
}

/* Dark Mode Toggle */
.theme-toggle {
  background: none;
  border: 2px solid var(--border-color);
  border-radius: var(--radius-full);
  width: 40px;
  height: 40px;
  cursor: pointer;
  display: flex;
  justify-content: center;
  align-items: center;
  transition: all var(--transition-fast);
  color: var(--text-primary);
  font-size: 1.2rem;
}

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

.theme-toggle svg {
  display: block;
  width: 20px;
  height: 20px;
  transition: transform var(--transition-base);
}

.theme-toggle:hover svg {
  transform: scale(1.1);
}

/* Mobile Hamburger Menu */
.hamburger {
  display: none;
  flex-direction: column;
  cursor: pointer;
  gap: 5px;
  padding: var(--spacing-sm);
  border: none;
  background: none;
}

.hamburger span {
  width: 25px;
  height: 3px;
  background-color: var(--text-primary);
  transition: all var(--transition-fast);
  border-radius: 2px;
}

.hamburger.active span:nth-child(1) {
  transform: rotate(45deg) translate(7px, 7px);
}

.hamburger.active span:nth-child(2) {
  opacity: 0;
}

.hamburger.active span:nth-child(3) {
  transform: rotate(-45deg) translate(7px, -7px);
}

/* ============================================
   Container and Layout
   ============================================ */
.container {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: var(--spacing-xl) var(--spacing-lg);
}

.section {
  padding: var(--spacing-3xl) 0;
}

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

.section-subtitle {
  text-align: center;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-2xl);
  max-width: 700px;
  margin-left: auto;
  margin-right: auto;
}

/* ============================================
   Grid System
   ============================================ */
.grid {
  display: grid;
  gap: var(--spacing-xl);
}

.grid-2 {
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
}

.grid-3 {
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
}

.grid-4 {
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
}

/* ============================================
   Cards
   ============================================ */
.card {
  background-color: var(--bg-secondary);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  box-shadow: 0 2px 8px var(--shadow-light);
  transition: transform var(--transition-base), box-shadow var(--transition-base);
  border: 1px solid var(--border-color);
}

.card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 20px var(--shadow-medium);
}

.card-title {
  font-size: 1.25rem;
  margin-bottom: var(--spacing-sm);
}

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

.card-link {
  color: var(--accent-primary);
  font-weight: 500;
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.card-link:hover {
  color: var(--accent-hover);
}

/* Tool Cards */
.tool-card {
  position: relative;
}

.tool-card.coming-soon {
  opacity: 0.8;
}

.tool-ui input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  background: var(--border-color);
  outline: none;
  border-radius: var(--radius-full);
  height: 8px;
}

.tool-ui input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 20px;
  height: 20px;
  background: var(--accent-primary);
  border-radius: 50%;
  cursor: pointer;
}

.tool-ui input[type="range"]::-moz-range-thumb {
  width: 20px;
  height: 20px;
  background: var(--accent-primary);
  border-radius: 50%;
  cursor: pointer;
  border: none;
}

.tool-ui input[type="checkbox"] {
  cursor: pointer;
  width: 18px;
  height: 18px;
}

.tool-ui select,
.tool-ui input[type="text"],
.tool-ui input[type="url"],
.tool-ui textarea {
  transition: border-color var(--transition-fast);
}

.tool-ui select:focus,
.tool-ui input[type="text"]:focus,
.tool-ui input[type="url"]:focus,
.tool-ui textarea:focus {
  outline: none;
  border-color: var(--accent-primary);
}

/* ============================================
   Buttons
   ============================================ */
.btn {
  display: inline-block;
  padding: var(--spacing-md) var(--spacing-xl);
  border-radius: var(--radius-md);
  font-weight: 600;
  text-align: center;
  cursor: pointer;
  border: none;
  transition: all var(--transition-fast);
  text-decoration: none;
  font-size: 1rem;
}

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

.btn-primary:hover {
  background-color: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px var(--shadow-medium);
}

.btn-secondary {
  background-color: transparent;
  color: var(--accent-primary);
  border: 2px solid var(--accent-primary);
}

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

.btn-large {
  padding: var(--spacing-lg) var(--spacing-2xl);
  font-size: 1.1rem;
}

.btn-block {
  width: 100%;
  display: block;
}

/* ============================================
   Forms
   ============================================ */
.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-label {
  display: block;
  margin-bottom: var(--spacing-sm);
  font-weight: 600;
  color: var(--text-primary);
}

.form-input,
.form-textarea,
.form-select {
  width: 100%;
  padding: var(--spacing-md);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-family: inherit;
  font-size: 1rem;
  background-color: var(--bg-primary);
  color: var(--text-primary);
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.form-input:focus,
.form-textarea:focus,
.form-select:focus {
  outline: none;
  border-color: var(--accent-primary);
  box-shadow: 0 0 0 3px var(--shadow-light);
}

.form-textarea {
  resize: vertical;
  min-height: 120px;
}

.form-error {
  color: var(--danger);
  font-size: 0.875rem;
  margin-top: var(--spacing-xs);
  display: none;
}

.form-group.error .form-input,
.form-group.error .form-textarea,
.form-group.error .form-select {
  border-color: var(--danger);
}

.form-group.error .form-error {
  display: block;
}

/* ============================================
   Hero Section
   ============================================ */
.hero {
  padding: var(--spacing-3xl) 0;
  text-align: center;
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
}

.hero-content {
  max-width: 800px;
  margin: 0 auto;
}

.hero-title {
  font-size: 3rem;
  margin-bottom: var(--spacing-lg);
  animation: fadeInUp 0.8s ease;
}

.hero-subtitle {
  font-size: 1.25rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-xl);
  animation: fadeInUp 0.8s ease 0.2s backwards;
}

.hero-buttons {
  display: flex;
  gap: var(--spacing-lg);
  justify-content: center;
  flex-wrap: wrap;
  animation: fadeInUp 0.8s ease 0.4s backwards;
}

@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(30px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

/* ============================================
   Filter Buttons
   ============================================ */
.filter-buttons {
  display: flex;
  gap: var(--spacing-md);
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: var(--spacing-2xl);
}

.filter-btn {
  padding: var(--spacing-sm) var(--spacing-lg);
  border: 2px solid var(--border-color);
  background-color: transparent;
  color: var(--text-primary);
  border-radius: var(--radius-full);
  cursor: pointer;
  font-weight: 500;
  transition: all var(--transition-fast);
}

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

/* ============================================
   Skills Section
   ============================================ */
.skill-category {
  margin-bottom: var(--spacing-2xl);
}

.skill-items {
  display: flex;
  flex-wrap: wrap;
  gap: var(--spacing-md);
}

.skill-item {
  padding: var(--spacing-sm) var(--spacing-lg);
  background-color: var(--bg-secondary);
  border-radius: var(--radius-full);
  border: 2px solid var(--border-color);
  font-weight: 500;
  transition: all var(--transition-fast);
}

.skill-item:hover {
  background-color: var(--accent-primary);
  color: #ffffff;
  border-color: var(--accent-primary);
  transform: translateY(-2px);
}

/* ============================================
   Timeline (for Resume)
   ============================================ */
.timeline {
  position: relative;
  padding: var(--spacing-xl) 0;
}

.timeline::before {
  content: '';
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  width: 2px;
  height: 100%;
  background-color: var(--border-color);
}

.timeline-item {
  position: relative;
  margin-bottom: var(--spacing-2xl);
  display: flex;
  align-items: center;
}

.timeline-item:nth-child(odd) {
  flex-direction: row;
}

.timeline-item:nth-child(even) {
  flex-direction: row-reverse;
}

.timeline-content {
  width: 45%;
  padding: var(--spacing-lg);
  background-color: var(--bg-secondary);
  border-radius: var(--radius-lg);
  box-shadow: 0 2px 8px var(--shadow-light);
  border: 1px solid var(--border-color);
}

.timeline-dot {
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
  width: 20px;
  height: 20px;
  background-color: var(--accent-primary);
  border: 4px solid var(--bg-primary);
  border-radius: 50%;
  z-index: 1;
}

.timeline-date {
  color: var(--accent-primary);
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
}

/* ============================================
   Blog Post
   ============================================ */
.blog-post-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
  padding: var(--spacing-2xl) 0;
  background: linear-gradient(135deg, var(--bg-secondary) 0%, var(--bg-tertiary) 100%);
}

.blog-post-meta {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-md);
}

.blog-post-content {
  max-width: 800px;
  margin: 0 auto;
  line-height: 1.8;
}

.blog-post-content img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-lg);
  margin: var(--spacing-xl) 0;
}

.blog-post-content code {
  background-color: var(--bg-secondary);
  padding: var(--spacing-xs) var(--spacing-sm);
  border-radius: var(--radius-sm);
  font-family: var(--font-mono);
  font-size: 0.9rem;
}

.blog-post-content pre {
  background-color: var(--bg-secondary);
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  overflow-x: auto;
  margin: var(--spacing-lg) 0;
}

.blog-post-content pre code {
  background-color: transparent;
  padding: 0;
}

/* ============================================
   Back to Top Button
   ============================================ */
.back-to-top {
  position: fixed;
  bottom: 30px;
  right: 30px;
  width: 50px;
  height: 50px;
  background-color: var(--accent-primary);
  color: #ffffff;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  justify-content: center;
  align-items: center;
  font-size: 1.5rem;
  box-shadow: 0 4px 12px var(--shadow-medium);
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-base);
  z-index: 999;
}

.back-to-top.visible {
  opacity: 1;
  visibility: visible;
}

.back-to-top:hover {
  background-color: var(--accent-hover);
  transform: translateY(-5px);
}

.back-to-top svg {
  display: block;
  width: 20px;
  height: 20px;
}

/* ============================================
   Footer
   ============================================ */
.site-footer {
  background-color: var(--bg-secondary);
  padding: var(--spacing-2xl) 0;
  margin-top: var(--spacing-3xl);
  border-top: 1px solid var(--border-color);
}

.footer-content {
  max-width: var(--container-max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-xl);
}

.footer-section h4 {
  margin-bottom: var(--spacing-md);
}

.footer-links {
  list-style: none;
}

.footer-links li {
  margin-bottom: var(--spacing-sm);
}

.footer-links a {
  color: var(--text-secondary);
  transition: color var(--transition-fast);
}

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

.footer-bottom {
  text-align: center;
  margin-top: var(--spacing-xl);
  padding-top: var(--spacing-xl);
  border-top: 1px solid var(--border-color);
  color: var(--text-secondary);
}

/* ============================================
   Responsive Design
   ============================================ */
@media (max-width: 768px) {
  .nav-menu {
    position: fixed;
    top: var(--header-height);
    left: -100%;
    width: 100%;
    height: calc(100vh - var(--header-height));
    background-color: var(--bg-primary);
    flex-direction: column;
    align-items: flex-start;
    padding: var(--spacing-xl);
    transition: left var(--transition-base);
    box-shadow: 0 4px 12px var(--shadow-medium);
    overflow-y: auto;
  }

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

  .hamburger {
    display: flex;
  }

  .hero-title {
    font-size: 2rem;
  }

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

  .hero-buttons {
    flex-direction: column;
    align-items: stretch;
  }

  .timeline::before {
    left: 20px;
  }

  .timeline-item {
    flex-direction: row !important;
    padding-left: 50px;
  }

  .timeline-content {
    width: 100%;
  }

  .timeline-dot {
    left: 20px;
  }

  h1 {
    font-size: 2rem;
  }

  h2 {
    font-size: 1.75rem;
  }

  h3 {
    font-size: 1.5rem;
  }

  .grid-2,
  .grid-3,
  .grid-4 {
    grid-template-columns: 1fr;
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: 1.5rem;
  }

  .btn-large {
    padding: var(--spacing-md) var(--spacing-lg);
    font-size: 1rem;
  }

  .back-to-top {
    width: 40px;
    height: 40px;
    bottom: 20px;
    right: 20px;
  }
}

/* ============================================
   Utility Classes
   ============================================ */
.text-center {
  text-align: center;
}

.text-left {
  text-align: left;
}

.text-right {
  text-align: right;
}

.mt-0 {
  margin-top: 0;
}

.mb-0 {
  margin-bottom: 0;
}

.mt-1 {
  margin-top: var(--spacing-md);
}

.mb-1 {
  margin-bottom: var(--spacing-md);
}

.mt-2 {
  margin-top: var(--spacing-lg);
}

.mb-2 {
  margin-bottom: var(--spacing-lg);
}

.mt-3 {
  margin-top: var(--spacing-xl);
}

.mb-3 {
  margin-bottom: var(--spacing-xl);
}

.d-none {
  display: none;
}

.d-block {
  display: block;
}

.d-flex {
  display: flex;
}

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

.align-center {
  align-items: center;
}

.gap-1 {
  gap: var(--spacing-md);
}

.gap-2 {
  gap: var(--spacing-lg);
}

.gap-3 {
  gap: var(--spacing-xl);
}

/* ============================================
   Animations
   ============================================ */
.fade-in {
  opacity: 1 !important;
  animation: fadeIn 0.5s ease;
  transition: opacity 0.3s ease;
}

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

.slide-in-left {
  animation: slideInLeft 0.5s ease;
}

@keyframes slideInLeft {
  from {
    opacity: 0;
    transform: translateX(-30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.slide-in-right {
  animation: slideInRight 0.5s ease;
}

@keyframes slideInRight {
  from {
    opacity: 0;
    transform: translateX(30px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.scale-in {
  animation: scaleIn 0.3s ease;
}

@keyframes scaleIn {
  from {
    opacity: 0;
    transform: scale(0.9);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

/* ============================================
   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-width: 0;
}

*:focus-visible {
  outline: 2px solid var(--accent-primary);
  outline-offset: 2px;
}

/* ============================================
   Print Styles
   ============================================ */
@media print {
  .site-header,
  .site-footer,
  .back-to-top,
  .hamburger,
  .theme-toggle {
    display: none;
  }

  body {
    font-size: 12pt;
    color: #000;
    background: #fff;
  }

  a {
    color: #000;
    text-decoration: underline;
  }
}