@view-transition {
  navigation: auto;
}

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  height: 100%;
}

body {
  box-sizing: border-box;
  font-family: 'Inter', sans-serif;
  margin: 0;
  padding: 0;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  min-height: 100%;
  height: 100%;
}

/* Header styles */
.header {
  background: linear-gradient(135deg, #059669 0%, #047857 100%);
  backdrop-filter: blur(10px);
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 4px 20px rgba(5, 150, 105, 0.15);
}

/* Desktop nav */
.main-nav-center {
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
}

.header .nav-links {
  align-items: center;
}

/* Dropdown */
.dropdown {
  position: relative;
}

.dropdown-content {
  display: none;
  position: absolute;
  top: 100%;
  right: 0;
  background: white;
  min-width: 220px;
  box-shadow: 0 8px 30px rgba(0,0,0,0.12);
  border-radius: 12px;
  margin-top: 8px;
  overflow: hidden;
  animation: fadeInDown 0.3s ease;
  z-index: 1200;
}

.dropdown.open .dropdown-content {
  display: block;
}

.dropdown-content a {
  color: #4a5568;
  padding: 12px 20px;
  text-decoration: none;
  display: block;
  transition: all 0.3s ease;
  font-size: 14px;
}

.dropdown-content a:hover {
  background: linear-gradient(135deg, #059669 0%, #047857 100%);
  color: white;
  padding-left: 28px;
}

/* Mobile menu toggle button */
.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: white;
  font-size: 24px;
  cursor: pointer;
}

/* Mobile slide-down menu */
.mobile-menu-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.45);
  z-index: 900;
  display: none;
}

.mobile-menu-overlay.open {
  display: block;
}

.mobile-menu {
  position: fixed;
  top: 70px;
  left: 16px;
  right: 16px;
  background: linear-gradient(135deg, #059669 0%, #047857 100%);
  border-radius: 18px;
  padding: 16px 20px;
  box-shadow: 0 15px 45px rgba(0,0,0,0.4);
  z-index: 901;
  display: none;
}

.mobile-menu.open {
  display: block;
}

.mobile-menu a {
  display: block;
  color: #ffffff;
  padding: 10px 4px;
  text-decoration: none;
  font-weight: 500;
  border-bottom: 1px solid rgba(255,255,255,0.15);
}

.mobile-menu a:last-child {
  border-bottom: none;
}

.mobile-menu a:hover {
  color: #e2e8f0;
  padding-left: 8px;
}

/* Page Header */
.page-header {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 80px 20px;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.page-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 1200 120'%3E%3Cpath d='M0,0 Q300,60 600,30 T1200,0 L1200,120 L0,120 Z' fill='rgba(255,255,255,0.05)'/%3E%3C/svg%3E") repeat-x bottom;
  background-size: 1200px 120px;
  opacity: 0.3;
}

.page-header h1 {
  font-size: 56px;
  font-weight: 900;
  margin-bottom: 16px;
  position: relative;
  z-index: 1;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
  animation: slideInDown 0.6s ease;
}

.page-header p {
  font-size: 22px;
  opacity: 0.95;
  position: relative;
  z-index: 1;
  animation: slideInUp 0.6s ease;
}

/* Calculator Container */
.calculator-container {
  max-width: 1200px;
  margin: -60px auto 60px;
  padding: 0 20px;
  position: relative;
  z-index: 10;
}

.calculator-card {
  background: white;
  border-radius: 24px;
  padding: 40px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.15);
  animation: slideUp 0.6s ease;
}

/* Mode Selection */
.mode-tabs {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  margin-bottom: 32px;
}

.mode-tab {
  padding: 16px 24px;
  background: white;
  border: 3px solid #e2e8f0;
  border-radius: 12px;
  cursor: pointer;
  transition: all 0.3s ease;
  text-align: center;
  font-weight: 600;
  color: #4a5568;
  font-size: 15px;
}

.mode-tab:hover {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border-color: #667eea;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}

.mode-tab.active {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border-color: #667eea;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

/* Form Styles */
.form-group {
  margin-bottom: 24px;
}

.form-label {
  display: block;
  font-weight: 600;
  color: #2d3748;
  margin-bottom: 8px;
  font-size: 15px;
}

.form-input {
  width: 100%;
  padding: 14px 18px;
  border: 2px solid #e2e8f0;
  border-radius: 12px;
  font-size: 18px;
  font-weight: 600;
  transition: all 0.3s ease;
  font-family: 'Inter', sans-serif;
}

.form-input:focus {
  outline: none;
  border-color: #667eea;
  box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.1);
  transform: translateY(-2px);
}

.input-hint {
  font-size: 13px;
  color: #718096;
  margin-top: 6px;
  font-style: italic;
}

.calculate-btn {
  width: 100%;
  padding: 16px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  border: none;
  border-radius: 12px;
  font-size: 18px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: 0 4px 15px rgba(102, 126, 234, 0.4);
}

.calculate-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.5);
}

.calculate-btn:active {
  transform: translateY(0);
}

/* Result Display */
.result-container {
  margin-top: 32px;
  display: none;
  animation: resultSlide 0.5s ease;
}

.result-container.show {
  display: block;
}

.result-card {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  padding: 40px;
  border-radius: 16px;
  color: white;
  text-align: center;
  margin-bottom: 24px;
  box-shadow: 0 8px 25px rgba(102, 126, 234, 0.4);
}

.result-label {
  font-size: 16px;
  opacity: 0.9;
  text-transform: uppercase;
  letter-spacing: 1px;
  margin-bottom: 16px;
  font-weight: 600;
}

.result-value {
  font-size: 56px;
  font-weight: 900;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
  animation: pulse 2s ease-in-out infinite;
  margin-bottom: 12px;
  word-break: break-all;
}

.result-details {
  background: #f7fafc;
  padding: 28px;
  border-radius: 16px;
  margin-bottom: 24px;
}

.detail-section {
  margin-bottom: 20px;
}

.detail-section:last-child {
  margin-bottom: 0;
}

.detail-title {
  font-size: 16px;
  font-weight: 700;
  color: #2d3748;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.detail-content {
  color: #4a5568;
  line-height: 1.8;
  font-size: 15px;
}

.formula-display {
  background: #2d3748;
  color: #e2e8f0;
  padding: 20px;
  border-radius: 12px;
  font-family: 'Courier New', monospace;
  margin: 16px 0;
  overflow-x: auto;
  font-size: 16px;
}

.download-buttons {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

.download-btn {
  flex: 1;
  min-width: 140px;
  padding: 12px 24px;
  background: white;
  color: #667eea;
  border: 2px solid #667eea;
  border-radius: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.3s ease;
  font-size: 16px;
}

.download-btn:hover {
  background: #667eea;
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}

.step-item {
  background: white;
  padding: 16px;
  border-radius: 8px;
  margin-bottom: 12px;
  border-left: 4px solid #667eea;
}

.step-item:last-child {
  margin-bottom: 0;
}

/* Info Cards */
.info-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
  margin-top: 40px;
}

.info-card {
  background: white;
  padding: 28px;
  border-radius: 16px;
  box-shadow: 0 4px 20px rgba(0,0,0,0.08);
  transition: all 0.3s ease;
  border-left: 4px solid #667eea;
}

.info-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 30px rgba(102, 126, 234, 0.2);
}

.info-card h3 {
  font-size: 20px;
  font-weight: 700;
  color: #2d3748;
  margin-bottom: 12px;
}

.info-card p {
  color: #4a5568;
  line-height: 1.7;
  font-size: 15px;
}

/* Blog Section */
.blog-section {
  max-width: 900px;
  margin: 80px auto;
  padding: 0 20px;
}

.blog-content {
  background: white;
  border-radius: 24px;
  padding: 60px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.1);
  line-height: 1.8;
}

.blog-content h2 {
  font-size: 42px;
  font-weight: 900;
  color: #1a202c;
  margin-bottom: 32px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.blog-content h3 {
  font-size: 28px;
  font-weight: 700;
  color: #2d3748;
  margin-top: 40px;
  margin-bottom: 20px;
}

.blog-content h4 {
  font-size: 22px;
  font-weight: 600;
  color: #4a5568;
  margin-top: 32px;
  margin-bottom: 16px;
}

.blog-content p {
  color: #4a5568;
  font-size: 17px;
  margin-bottom: 24px;
  line-height: 1.9;
}

.blog-content ul,
.blog-content ol {
  color: #4a5568;
  margin-left: 32px;
  margin-bottom: 24px;
}

.blog-content li {
  margin-bottom: 12px;
  line-height: 1.8;
}

.blog-content strong {
  color: #667eea;
  font-weight: 700;
}

.blog-content em {
  font-style: italic;
  color: #764ba2;
}

.highlight-box {
  background: linear-gradient(135deg, #f3f4ff 0%, #f8f5ff 100%);
  padding: 24px;
  border-radius: 12px;
  border-left: 4px solid #667eea;
  margin: 32px 0;
}

.formula-box {
  background: #2d3748;
  color: #e2e8f0;
  padding: 20px;
  border-radius: 12px;
  font-family: 'Courier New', monospace;
  margin: 24px 0;
  overflow-x: auto;
}

/* FAQ visible styling */
.faq-item {
  border-left: 4px solid #667eea;
  padding: 16px 18px;
  margin-bottom: 16px;
  background: #f7fafc;
  border-radius: 10px;
}

.faq-item h4 {
  margin-top: 0;
  margin-bottom: 8px;
  font-size: 18px;
  color: #2d3748;
}

.faq-item p {
  margin: 0;
  font-size: 15px;
  color: #4a5568;
}

/* Footer styles */
.footer {
  background: linear-gradient(135deg, #2d3748 0%, #1a202c 100%);
  color: white;
  padding: 60px 0 20px;
  margin-top: 80px;
}

.footer-column h3 {
  font-size: 18px;
  font-weight: 700;
  margin-bottom: 20px;
  color: #a0aec0;
  text-transform: uppercase;
  letter-spacing: 1px;
}

.footer-column ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.footer-column ul li {
  margin-bottom: 12px;
}

.footer-column ul li a {
  color: #cbd5e0;
  text-decoration: none;
  transition: all 0.3s ease;
  display: inline-block;
}

.footer-column ul li a:hover {
  color: #667eea;
  transform: translateX(5px);
}

.footer-bottom {
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  margin-top: 40px;
  padding-top: 30px;
  text-align: center;
  color: #a0aec0;
}

/* Shared utility */
.input-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 20px;
}

.subscript {
  font-size: 0.7em;
  vertical-align: sub;
}

/* Animations */
@keyframes fadeInDown {
  from {
    opacity: 0;
    transform: translateY(-10px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

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

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

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

@keyframes resultSlide {
  from {
    opacity: 0;
    transform: scale(0.95);
  }
  to {
    opacity: 1;
    transform: scale(1);
  }
}

@keyframes pulse {
  0%, 100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.05);
  }
}

/* Responsive */
@media (max-width: 768px) {
  /* Hide desktop nav on mobile */
  .header .nav-links {
    display: none !important;
  }

  .mobile-menu-btn {
    display: block;
  }

  .page-header h1 {
    font-size: 32px;
  }

  .page-header p {
    font-size: 18px;
  }

  .calculator-card {
    padding: 24px;
  }

  .result-value {
    font-size: 40px;
  }

  .blog-content {
    padding: 32px 24px;
  }

  .blog-content h2 {
    font-size: 30px;
  }

  .blog-content h3 {
    font-size: 22px;
  }

  .download-buttons {
    flex-direction: column;
  }

  .download-btn {
    width: 100%;
  }

  .mode-tabs {
    grid-template-columns: 1fr;
  }
}