@view-transition {
  navigation: auto;
}

*,
*::before,
*::after {
  box-sizing: border-box;
}

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

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

/* Header */

.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);
}

.header-inner {
  position: relative;
}

.site-logo {
  width: 36px;
  height: 36px;
  border-radius: 8px;
  object-fit: contain;
}

.site-title-link {
  text-decoration: none;
  color: #ffffff;
  font-size: 1.1rem;
  font-weight: 700;
}

/* Desktop navigation */

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

.desktop-nav-center {
  position: absolute;
  left: 50%;
  transform: translateX(-50%);
}

.nav-link {
  color: #ffffff;
  font-weight: 500;
  text-decoration: none;
  transition: all 0.3s ease;
  display: inline-block;
}

.nav-link:hover {
  color: #e5e7eb;
  transform: scale(1.08);
}

/* Dropdown */

.dropdown {
  position: relative;
}

.dropdown-toggle {
  background: none;
  border: none;
  color: #ffffff;
  font-weight: 500;
  cursor: pointer;
  padding: 6px 10px;
  border-radius: 999px;
  transition: background 0.2s ease, transform 0.2s ease;
}

.dropdown-toggle:hover {
  background: rgba(255, 255, 255, 0.12);
  transform: translateY(-1px);
}

.dropdown-content {
  display: none;
  position: absolute;
  top: 110%;
  right: 0;
  background: #ffffff;
  min-width: 220px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
  border-radius: 12px;
  margin-top: 8px;
  overflow: hidden;
  z-index: 1200;
}

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

.dropdown-content a {
  color: #4a5568;
  padding: 12px 20px;
  text-decoration: none;
  display: block;
  transition: all 0.25s ease;
  font-size: 14px;
}

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

/* Mobile menu */

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: #ffffff;
  font-size: 24px;
  cursor: pointer;
}

/* Slide-down mobile menu just under header */
.mobile-menu {
  display: block;
  background: linear-gradient(135deg, #059669 0%, #047857 100%);
  box-shadow: 0 10px 30px rgba(4, 120, 87, 0.35);
  max-height: 0;
  overflow: hidden;
  transition: max-height 0.3s ease, opacity 0.25s ease;
  opacity: 0;
  z-index: 900;
}

.mobile-menu.open {
  max-height: 420px;
  opacity: 1;
}

.mobile-menu-inner {
  display: flex;
  flex-direction: column;
  gap: 4px;
}

.mobile-menu-link {
  display: block;
  padding: 10px 0;
  text-decoration: none;
  color: #ecfdf5;
  font-weight: 500;
  border-radius: 8px;
  transition: background 0.2s ease, padding-left 0.2s ease;
}

.mobile-menu-link:hover {
  background: rgba(16, 185, 129, 0.22);
  padding-left: 8px;
}

.mobile-menu-divider {
  border: none;
  border-top: 1px solid rgba(209, 250, 229, 0.4);
  margin: 6px 0;
}

/* Page header */

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

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

.page-header h1 {
  font-size: 2.9rem;
  font-weight: 900;
  margin-bottom: 12px;
  position: relative;
  z-index: 1;
  text-shadow: 2px 2px 4px rgba(0, 0, 0, 0.25);
  animation: slideInDown 0.6s ease;
}

.page-header p {
  font-size: 1.25rem;
  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: #ffffff;
  border-radius: 24px;
  padding: 40px;
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.15);
  animation: slideUp 0.6s ease;
}

.intro-text {
  color: #4a5568;
  font-size: 16px;
  line-height: 1.7;
  margin-bottom: 32px;
  text-align: justify;
}

/* Mode toggle */

.mode-toggle {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: 12px;
  margin-bottom: 32px;
  background: #f7fafc;
  padding: 12px;
  border-radius: 16px;
}

.mode-btn {
  padding: 16px;
  background: transparent;
  border: 2px solid transparent;
  border-radius: 12px;
  cursor: pointer;
  font-weight: 600;
  color: #4a5568;
  transition: all 0.3s ease;
  font-size: 15px;
}

.mode-btn:hover {
  background: #edf2f7;
}

.mode-btn.active {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: #ffffff;
  border-color: #764ba2;
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
}

/* Input section */

.input-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 24px;
  margin-bottom: 32px;
}

.input-group {
  position: relative;
}

.input-label {
  display: flex;
  align-items: center;
  gap: 8px;
  font-weight: 600;
  color: #2d3748;
  margin-bottom: 12px;
  font-size: 16px;
}

.input-wrapper {
  position: relative;
}

.input-field {
  width: 100%;
  padding: 16px 48px 16px 16px;
  border: 2px solid #cbd5e0;
  border-radius: 12px;
  font-size: 18px;
  transition: all 0.3s ease;
  font-weight: 600;
}

.input-field:focus {
  outline: none;
  border-color: #764ba2;
  box-shadow: 0 0 0 3px rgba(118, 75, 162, 0.1);
}

.input-unit {
  position: absolute;
  right: 16px;
  top: 50%;
  transform: translateY(-50%);
  color: #718096;
  font-weight: 600;
  font-size: 14px;
}

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

/* Calculate button */

.calculate-btn {
  width: 100%;
  padding: 20px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: #ffffff;
  border: none;
  border-radius: 12px;
  font-size: 20px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.3s ease;
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.3);
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 12px;
}

.calculate-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(102, 126, 234, 0.4);
}

.calculate-btn:active {
  transform: scale(0.98);
}

/* Results */

.results-section {
  margin-top: 32px;
  padding: 32px;
  background: linear-gradient(135deg, #f3f4ff 0%, #e9e4f7 100%);
  border-radius: 16px;
  border-left: 4px solid #764ba2;
  display: none;
  animation: fadeIn 0.5s ease;
}

.results-section.show {
  display: block;
}

.result-title {
  font-size: 24px;
  font-weight: 700;
  color: #2d3748;
  margin-bottom: 24px;
  display: flex;
  align-items: center;
  gap: 12px;
}

.result-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 16px;
  margin-bottom: 24px;
}

.result-box {
  background: #ffffff;
  padding: 24px;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
  transition: all 0.3s ease;
}

.result-box:hover {
  transform: translateY(-4px);
  box-shadow: 0 8px 20px rgba(118, 75, 162, 0.15);
}

.result-label {
  font-weight: 600;
  color: #4a5568;
  font-size: 14px;
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 6px;
}

.result-value {
  font-weight: 700;
  color: #764ba2;
  font-size: 28px;
}

.result-unit {
  font-size: 16px;
  color: #718096;
  margin-left: 4px;
}

/* Error box */

.error-box {
  border-left: 4px solid #ef4444;
  grid-column: 1 / -1;
}

.error-label {
  color: #ef4444;
}

.error-text {
  color: #ef4444;
  font-size: 16px;
  margin-top: 8px;
}

/* Download buttons */

.download-buttons {
  display: flex;
  gap: 12px;
  margin-top: 24px;
}

.download-btn {
  flex: 1;
  padding: 14px 24px;
  background: linear-gradient(135deg, #10b981 0%, #059669 100%);
  color: #ffffff;
  border: none;
  border-radius: 10px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
}

.download-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
}

/* Breakdown */

.breakdown-card {
  background: #ffffff;
  padding: 28px;
  border-radius: 12px;
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.05);
}

.breakdown-title {
  font-size: 20px;
  font-weight: 700;
  color: #2d3748;
  margin-bottom: 20px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.breakdown-grid {
  display: grid;
  gap: 16px;
}

.breakdown-block {
  padding: 16px;
  border-radius: 10px;
  border-left: 4px solid transparent;
}

.breakdown-heading {
  font-weight: 600;
  color: #4a5568;
  margin-bottom: 8px;
}

.breakdown-text {
  color: #4a5568;
  line-height: 1.8;
  font-size: 14px;
}

.breakdown-metric {
  background: linear-gradient(135deg, #f3f4ff 0%, #e9e4f7 100%);
  border-left-color: #764ba2;
}

.breakdown-wheel {
  background: linear-gradient(135deg, #f0f9ff 0%, #e0f2fe 100%);
  border-left-color: #0ea5e9;
}

.breakdown-character {
  background: linear-gradient(135deg, #f0fdf4 0%, #dcfce7 100%);
  border-left-color: #10b981;
}

.breakdown-check {
  background: linear-gradient(135deg, #fef2f2 0%, #fee2e2 100%);
  border-left-color: #ef4444;
}

.breakdown-rpm {
  background: linear-gradient(135deg, #fefce8 0%, #fef9c3 100%);
  border-left-color: #eab308;
}

/* Info grid */

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

.info-card {
  background: #ffffff;
  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 #764ba2;
}

.info-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 8px 30px rgba(118, 75, 162, 0.2);
}

.info-card h3 {
  font-size: 20px;
  font-weight: 700;
  color: #2d3748;
  margin-bottom: 12px;
  display: flex;
  align-items: center;
  gap: 8px;
}

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

/* Blog */

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

.blog-content {
  background: #ffffff;
  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: 2.3rem;
  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: 1.6rem;
  font-weight: 700;
  color: #2d3748;
  margin-top: 40px;
  margin-bottom: 20px;
}

.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: #764ba2;
  font-weight: 700;
}

.blog-content a {
  color: #2563eb;
  text-decoration: none;
}

.blog-content a:hover {
  text-decoration: underline;
}

.highlight-box {
  background: linear-gradient(135deg, #f3f4ff 0%, #e9e4f7 100%);
  padding: 24px;
  border-radius: 12px;
  border-left: 4px solid #764ba2;
  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;
  line-height: 1.6;
}

.formula-box code {
  color: #bfdbfe;
}

/* FAQ visible section */

.faq-section {
  max-width: 900px;
  margin: 40px auto 80px;
  padding: 0 20px;
}

.faq-container {
  background: #ffffff;
  border-radius: 24px;
  padding: 40px 30px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.08);
}

.faq-container h2 {
  font-size: 1.9rem;
  margin-bottom: 24px;
  color: #1f2933;
}

.faq-item + .faq-item {
  margin-top: 18px;
  padding-top: 18px;
  border-top: 1px solid #e5e7eb;
}

.faq-item h3 {
  font-size: 1.1rem;
  margin-bottom: 6px;
  color: #111827;
}

.faq-item p {
  color: #4b5563;
  line-height: 1.7;
  font-size: 0.97rem;
}

.faq-item a {
  color: #2563eb;
  text-decoration: none;
}

.faq-item a:hover {
  text-decoration: underline;
}

/* Footer */

.footer {
  background: linear-gradient(135deg, #2d3748 0%, #1a202c 100%);
  color: #ffffff;
  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: #14b8a6;
  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;
}

/* Animations */

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

@keyframes pulse {
  0%,
  100% {
    transform: scale(1);
  }
  50% {
    transform: scale(1.1);
  }
}

.pulse-animation {
  animation: pulse 2s ease-in-out infinite;
}

/* Responsive */

@media (max-width: 1024px) {
  .desktop-nav-center {
    position: static;
    transform: none;
  }
}

@media (max-width: 768px) {
  .nav-links {
    display: none !important;
  }

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

  .header-inner {
    justify-content: space-between;
  }

  .page-header {
    padding: 60px 16px;
  }

  .page-header h1 {
    font-size: 2rem;
  }

  .page-header p {
    font-size: 1rem;
  }

  .calculator-card {
    padding: 24px;
  }

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

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

  .blog-content h2 {
    font-size: 1.8rem;
  }

  .blog-content h3 {
    font-size: 1.3rem;
  }

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

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

  .faq-container {
    padding: 28px 22px;
  }
}

@media (min-width: 769px) {
  .mobile-menu {
    display: none !important;
  }
}