/* ===== CSS Variables ===== */
:root {
  /* Light Theme Colors */
  --primary-color: #4f46e5;
  --primary-hover: #4338ca;
  --secondary-color: #10b981;
  --background-color: #ffffff;
  --surface-color: #f8fafc;
  --card-background: #ffffff;
  --text-primary: #1f2937;
  --text-secondary: #6b7280;
  --text-muted: #9ca3af;
  --border-color: #e5e7eb;
  --shadow-light: 0 1px 3px rgba(0, 0, 0, 0.1);
  --shadow-medium: 0 4px 6px rgba(0, 0, 0, 0.1);
  --shadow-large: 0 10px 15px rgba(0, 0, 0, 0.1);
  --gradient-primary: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  --gradient-secondary: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
  
  /* Spacing */
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  
  /* Border Radius */
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  
  /* Transitions */
  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;
}

/* Dark Theme Colors */
[data-theme="dark"] {
  --primary-color: #6366f1;
  --primary-hover: #5b21b6;
  --secondary-color: #059669;
  --background-color: #111827;
  --surface-color: #1f2937;
  --card-background: #374151;
  --text-primary: #f9fafb;
  --text-secondary: #d1d5db;
  --text-muted: #9ca3af;
  --border-color: #4b5563;
  --shadow-light: 0 1px 3px rgba(0, 0, 0, 0.3);
  --shadow-medium: 0 4px 6px rgba(0, 0, 0, 0.3);
  --shadow-large: 0 10px 15px rgba(0, 0, 0, 0.3);
}

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

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

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  line-height: 1.6;
  color: var(--text-primary);
  background-color: var(--background-color);
  transition: background-color var(--transition-normal), color var(--transition-normal);
}

/* ===== Navigation ===== */
.navbar {
  background: var(--card-background);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--border-color);
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 1000;
  transition: all var(--transition-normal);
}

.nav-container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 70px;
}

.nav-brand {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-weight: 600;
  font-size: 1.125rem;
  color: var(--text-primary);
  text-decoration: none;
}

.brand-icon {
  width: 32px;
  height: 32px;
}

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

.nav-link {
  color: var(--text-secondary);
  text-decoration: none;
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.nav-link:hover {
  color: var(--primary-color);
  background-color: var(--surface-color);
}

.nav-link.active {
  color: var(--primary-color);
  background-color: var(--surface-color);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--spacing-md);
}

.theme-toggle {
  background: none;
  border: none;
  padding: var(--spacing-sm);
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: all var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
}

.theme-toggle:hover {
  background-color: var(--surface-color);
}

.theme-icon {
  width: 20px;
  height: 20px;
}

.mobile-menu-toggle {
  display: none;
  background: none;
  border: none;
  font-size: 1.5rem;
  color: var(--text-primary);
  cursor: pointer;
  padding: var(--spacing-sm);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.mobile-menu-toggle:hover {
  background-color: var(--surface-color);
}

/* ===== Main Content ===== */
.main-content {
  padding-top: 70px;
  min-height: calc(100vh - 70px);
}

.page {
  display: none;
  animation: fadeIn var(--transition-normal);
}

.page.active {
  display: block;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: translateY(0); }
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

/* ===== Hero Section ===== */
.hero-section {
  background: var(--gradient-primary);
  color: white;
  padding: var(--spacing-2xl) 0;
  margin-bottom: var(--spacing-2xl);
}

.hero-section .container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
  align-items: center;
}

.hero-title {
  font-size: 3rem;
  font-weight: 700;
  margin-bottom: var(--spacing-lg);
  line-height: 1.2;
}

.hero-description {
  font-size: 1.25rem;
  margin-bottom: var(--spacing-xl);
  opacity: 0.9;
  line-height: 1.6;
}

.cta-button {
  background: rgba(255, 255, 255, 0.2);
  border: 2px solid rgba(255, 255, 255, 0.3);
  color: white;
  padding: var(--spacing-md) var(--spacing-xl);
  border-radius: var(--radius-lg);
  font-size: 1.125rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-normal);
  backdrop-filter: blur(10px);
}

.cta-button:hover {
  background: rgba(255, 255, 255, 0.3);
  border-color: rgba(255, 255, 255, 0.5);
  transform: translateY(-2px);
}

.calculator-preview {
  background: rgba(255, 255, 255, 0.1);
  border: 1px solid rgba(255, 255, 255, 0.2);
  border-radius: var(--radius-xl);
  padding: var(--spacing-xl);
  backdrop-filter: blur(10px);
}

.preview-screen {
  background: rgba(0, 0, 0, 0.2);
  border-radius: var(--radius-md);
  padding: var(--spacing-lg);
  font-family: 'Courier New', monospace;
}

.preview-line {
  margin-bottom: var(--spacing-sm);
  font-size: 1rem;
  opacity: 0.9;
}

/* ===== Features Section ===== */
.features-section {
  padding: var(--spacing-2xl) 0;
}

.section-title {
  text-align: center;
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-2xl);
  color: var(--text-primary);
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-xl);
}

.feature-card {
  background: var(--card-background);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
  text-align: center;
  transition: all var(--transition-normal);
  box-shadow: var(--shadow-light);
}

.feature-card:hover {
  transform: translateY(-5px);
  box-shadow: var(--shadow-large);
}

.feature-icon {
  font-size: 3rem;
  margin-bottom: var(--spacing-lg);
  display: block;
}

.feature-title {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: var(--spacing-md);
  color: var(--text-primary);
}

.feature-description {
  color: var(--text-secondary);
  line-height: 1.6;
}

/* ===== Calculator Page ===== */
.calculator-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
  padding: var(--spacing-xl) 0;
}

.page-title {
  font-size: 2.5rem;
  font-weight: 700;
  margin-bottom: var(--spacing-lg);
  color: var(--text-primary);
}

.page-description {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 600px;
  margin: 0 auto;
  line-height: 1.6;
}

.calculator-container {
  max-width: 900px;
  margin: 0 auto;
}

.calculator-card {
  background: var(--card-background);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  box-shadow: var(--shadow-medium);
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
}

/* ===== Form Styles ===== */
.form-group {
  margin-bottom: var(--spacing-xl);
}

.form-label {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  font-weight: 600;
  margin-bottom: var(--spacing-sm);
  color: var(--text-primary);
  font-size: 1rem;
}

.tooltip-btn {
  background: none;
  border: none;
  cursor: pointer;
  padding: 2px;
  border-radius: 50%;
  transition: all var(--transition-fast);
}

.tooltip-btn:hover {
  background-color: var(--surface-color);
}

.info-icon {
  width: 16px;
  height: 16px;
  opacity: 0.6;
}

.input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.input-prefix {
  position: absolute;
  left: var(--spacing-md);
  color: var(--text-secondary);
  font-weight: 500;
  z-index: 1;
}

.form-input {
  width: 100%;
  padding: var(--spacing-md);
  padding-left: calc(var(--spacing-md) + 20px);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  background: var(--background-color);
  color: var(--text-primary);
  transition: all var(--transition-fast);
}

.form-input:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.form-select {
  width: 100%;
  padding: var(--spacing-md);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  background: var(--background-color);
  color: var(--text-primary);
  cursor: pointer;
  transition: all var(--transition-fast);
}

.form-select:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.custom-rate-input {
  margin-top: var(--spacing-sm);
}

.toggle-container {
  display: flex;
  gap: var(--spacing-sm);
}

.toggle-container input[type="radio"] {
  display: none;
}

.toggle-label {
  flex: 1;
  padding: var(--spacing-md);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  text-align: center;
  cursor: pointer;
  transition: all var(--transition-fast);
  font-weight: 500;
  background: var(--background-color);
  color: var(--text-secondary);
}

.toggle-container input[type="radio"]:checked + .toggle-label {
  border-color: var(--primary-color);
  background: var(--primary-color);
  color: white;
}

.toggle-label:hover {
  border-color: var(--primary-color);
}

.reset-btn {
  background: var(--surface-color);
  border: 2px solid var(--border-color);
  color: var(--text-primary);
  padding: var(--spacing-md) var(--spacing-lg);
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 500;
  cursor: pointer;
  transition: all var(--transition-fast);
  width: 100%;
}

.reset-btn:hover {
  background: var(--border-color);
}

/* ===== Results Section ===== */
.results-section {
  background: var(--surface-color);
  border-radius: var(--radius-lg);
  padding: var(--spacing-xl);
}

.results-title {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: var(--spacing-lg);
  color: var(--text-primary);
  text-align: center;
}

.results-grid {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.result-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md);
  background: var(--card-background);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.result-item.total {
  background: var(--primary-color);
  color: white;
  border-color: var(--primary-color);
  font-weight: 600;
}

.result-label {
  font-weight: 500;
  color: inherit;
}

.result-value {
  font-weight: 600;
  font-size: 1.125rem;
  color: inherit;
}

/* ===== Contact Page ===== */
.contact-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
  padding: var(--spacing-xl) 0;
}

.contact-container {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--spacing-2xl);
  max-width: 1000px;
  margin: 0 auto;
}

.contact-form-section,
.contact-info-section {
  background: var(--card-background);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  box-shadow: var(--shadow-medium);
}

.contact-form {
  display: flex;
  flex-direction: column;
}

.form-textarea {
  width: 100%;
  padding: var(--spacing-md);
  border: 2px solid var(--border-color);
  border-radius: var(--radius-md);
  font-size: 1rem;
  background: var(--background-color);
  color: var(--text-primary);
  font-family: inherit;
  resize: vertical;
  min-height: 120px;
  transition: all var(--transition-fast);
}

.form-textarea:focus {
  outline: none;
  border-color: var(--primary-color);
  box-shadow: 0 0 0 3px rgba(79, 70, 229, 0.1);
}

.submit-btn {
  background: var(--primary-color);
  border: none;
  color: white;
  padding: var(--spacing-md) var(--spacing-xl);
  border-radius: var(--radius-md);
  font-size: 1.125rem;
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  margin-top: var(--spacing-md);
}

.submit-btn:hover {
  background: var(--primary-hover);
  transform: translateY(-1px);
}

.contact-info {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-lg);
}

.info-item {
  display: flex;
  align-items: flex-start;
  gap: var(--spacing-md);
  padding: var(--spacing-md);
  background: var(--surface-color);
  border-radius: var(--radius-md);
  transition: all var(--transition-fast);
}

.info-item:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-medium);
}

.info-icon {
  font-size: 1.5rem;
  margin-top: 2px;
}

.info-content h3 {
  font-size: 1.125rem;
  font-weight: 600;
  margin-bottom: var(--spacing-xs);
  color: var(--text-primary);
}

.info-content p {
  color: var(--text-secondary);
  margin: 0;
}

/* ===== Privacy Page ===== */
.privacy-header {
  text-align: center;
  margin-bottom: var(--spacing-2xl);
  padding: var(--spacing-xl) 0;
}

.privacy-content {
  max-width: 800px;
  margin: 0 auto;
  background: var(--card-background);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-xl);
  padding: var(--spacing-2xl);
  box-shadow: var(--shadow-medium);
}

.privacy-section {
  margin-bottom: var(--spacing-2xl);
}

.privacy-title {
  font-size: 1.5rem;
  font-weight: 600;
  margin-bottom: var(--spacing-lg);
  color: var(--text-primary);
}

.privacy-text {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-md);
  line-height: 1.7;
}

.privacy-list {
  list-style: none;
  padding-left: 0;
}

.privacy-list li {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-sm);
  padding-left: var(--spacing-lg);
  position: relative;
  line-height: 1.6;
}

.privacy-list li::before {
  content: "✓";
  position: absolute;
  left: 0;
  color: var(--secondary-color);
  font-weight: bold;
}

.privacy-footer {
  border-top: 1px solid var(--border-color);
  padding-top: var(--spacing-lg);
  text-align: center;
}

.privacy-date {
  color: var(--text-muted);
  font-style: italic;
}

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

.footer-content {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-2xl);
  margin-bottom: var(--spacing-xl);
}

.footer-section h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: var(--spacing-lg);
  color: var(--text-primary);
}

.footer-description {
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
}

.social-links {
  display: flex;
  gap: var(--spacing-md);
}

.social-link {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  background: var(--card-background);
  border: 1px solid var(--border-color);
  border-radius: 50%;
  color: var(--text-secondary);
  text-decoration: none;
  transition: all var(--transition-fast);
}

.social-link:hover {
  background: var(--primary-color);
  color: white;
  border-color: var(--primary-color);
  transform: translateY(-2px);
}

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

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

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  transition: color var(--transition-fast);
}

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

.footer-contacts li {
  color: var(--text-secondary);
}

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

.footer-bottom p {
  color: var(--text-muted);
  margin: 0;
}

/* ===== Scroll to Top Button ===== */
.scroll-to-top {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 50px;
  height: 50px;
  background: var(--primary-color);
  color: white;
  border: none;
  border-radius: 50%;
  cursor: pointer;
  font-size: 1.2rem;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-normal);
  z-index: 1000;
  box-shadow: var(--shadow-medium);
}

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

.scroll-to-top:hover {
  background: var(--primary-hover);
  transform: translateY(-2px);
}

/* ===== Tooltip ===== */
.tooltip {
  position: absolute;
  background: var(--text-primary);
  color: var(--background-color);
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-sm);
  font-size: 0.875rem;
  font-weight: 500;
  white-space: nowrap;
  z-index: 1000;
  opacity: 0;
  visibility: hidden;
  transition: all var(--transition-fast);
  pointer-events: none;
}

.tooltip.visible {
  opacity: 1;
  visibility: visible;
}

.tooltip::after {
  content: '';
  position: absolute;
  bottom: -5px;
  left: 50%;
  transform: translateX(-50%);
  width: 0;
  height: 0;
  border-left: 5px solid transparent;
  border-right: 5px solid transparent;
  border-top: 5px solid var(--text-primary);
}

/* ===== Responsive Design ===== */
@media (max-width: 768px) {
  .nav-menu {
    display: none;
  }
  
  .mobile-menu-toggle {
    display: block;
  }
  
  .hero-section .container {
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
    text-align: center;
  }
  
  .hero-title {
    font-size: 2.5rem;
  }
  
  .hero-description {
    font-size: 1.125rem;
  }
  
  .features-grid {
    grid-template-columns: 1fr;
    gap: var(--spacing-lg);
  }
  
  .calculator-card {
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
    padding: var(--spacing-xl);
  }
  
  .contact-container {
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
  }
  
  .footer-content {
    grid-template-columns: 1fr;
    gap: var(--spacing-xl);
    text-align: center;
  }
  
  .social-links {
    justify-content: center;
  }
  
  .page-title {
    font-size: 2rem;
  }
  
  .section-title {
    font-size: 2rem;
  }
  
  .container {
    padding: 0 var(--spacing-sm);
  }
}

@media (max-width: 480px) {
  .hero-title {
    font-size: 2rem;
  }
  
  .hero-description {
    font-size: 1rem;
  }
  
  .calculator-card,
  .contact-form-section,
  .contact-info-section,
  .privacy-content {
    padding: var(--spacing-lg);
  }
  
  .nav-container {
    padding: 0 var(--spacing-sm);
  }
  
  .brand-text {
    font-size: 1rem;
  }
  
  .toggle-container {
    flex-direction: column;
  }
  
  .cta-button {
    width: 100%;
  }
}

/* ===== Animations ===== */
@keyframes pulse {
  0%, 100% { opacity: 1; }
  50% { opacity: 0.5; }
}

@keyframes slideIn {
  from { transform: translateX(-100%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}

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

.feature-card {
  animation: slideUp 0.6s ease forwards;
}

.feature-card:nth-child(1) { animation-delay: 0.1s; }
.feature-card:nth-child(2) { animation-delay: 0.2s; }
.feature-card:nth-child(3) { animation-delay: 0.3s; }
.feature-card:nth-child(4) { animation-delay: 0.4s; }
.feature-card:nth-child(5) { animation-delay: 0.5s; }
.feature-card:nth-child(6) { animation-delay: 0.6s; }

/* ===== Loading States ===== */
.loading {
  animation: pulse 1.5s infinite;
}

/* ===== Focus Styles for Accessibility ===== */
button:focus,
input:focus,
select:focus,
textarea:focus,
.nav-link:focus,
.social-link:focus {
  outline: 2px solid var(--primary-color);
  outline-offset: 2px;
}

/* ===== Print Styles ===== */
@media print {
  .navbar,
  .footer,
  .scroll-to-top,
  .theme-toggle,
  .mobile-menu-toggle {
    display: none !important;
  }
  
  .main-content {
    padding-top: 0;
  }
  
  .page {
    display: block !important;
  }
  
  body {
    background: white !important;
    color: black !important;
  }
}