body {
  box-sizing: border-box;
  font-family: 'Inter', sans-serif;
  margin: 0;
  padding: 0;
  background: linear-gradient(135deg, #f5f7fa 0%, #c3cfe2 100%);
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; height: 100%; }
body { 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);
}

.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: 50;
}
.dropdown:hover .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;
}
@keyframes fadeInDown {
  from { opacity: 0; transform: translateY(-10px); }
  to { opacity: 1; transform: translateY(0); }
}

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

/* Mobile nav container */
.mobile-nav {
  display: none;
  background: #065f46;
}
.mobile-nav.open {
  display: block;
}
.mobile-nav-inner {
  max-width: 1120px;
  margin: 0 auto;
  padding: 8px 24px 16px;
}
.mobile-nav a {
  display: block;
  color: #e5e7eb;
  padding: 10px 0;
  border-bottom: 1px solid rgba(255,255,255,0.08);
  font-size: 15px;
  text-decoration: none;
}
.mobile-nav a:last-child {
  border-bottom: none;
}
.mobile-nav a:hover {
  color: #ffffff;
}

/* Page Header */
.page-header {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: 80px 20px 60px;
  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,<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: 56px;
  font-weight: 900;
  margin-bottom: 16px;
  position: relative;
  z-index: 1;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}
.page-header p {
  font-size: 22px;
  opacity: 0.95;
  position: relative;
  z-index: 1;
  max-width: 720px;
  margin: 0 auto;
}

/* Ad slots */
.ad-slot {
  margin: 24px 0;
  text-align: center;
}
.ad-label {
  font-size: 11px;
  color: #a0aec0;
  margin-bottom: 4px;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

/* Calculator Container */
.calculator-container {
  max-width: 1200px;
  margin: -40px 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;
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(30px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Tab Navigation */
.tab-navigation {
  display: flex;
  gap: 12px;
  margin-bottom: 32px;
  flex-wrap: wrap;
  border-bottom: 2px solid #e2e8f0;
  padding-bottom: 16px;
}
.tab-btn {
  padding: 12px 24px;
  border: none;
  background: #f7fafc;
  color: #4a5568;
  border-radius: 12px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.3s ease;
  font-size: 15px;
}
.tab-btn:hover {
  background: #e2e8f0;
  transform: translateY(-2px);
}
.tab-btn.active {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}
.tab-content { display: none; animation: fadeIn 0.4s ease; }
.tab-content.active { display: block; }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }

/* 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: 16px;
  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);
}
.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;
  padding: 32px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  border-radius: 16px;
  color: white;
  display: none;
  animation: resultSlide 0.5s ease;
}
.result-container.show { display: block; }
@keyframes resultSlide {
  from { opacity: 0; transform: scale(0.95); }
  to { opacity: 1; transform: scale(1); }
}
.result-value {
  font-size: 56px;
  font-weight: 900;
  margin-bottom: 16px;
  text-shadow: 2px 2px 4px rgba(0,0,0,0.2);
}
.result-label {
  font-size: 18px;
  opacity: 0.95;
  margin-bottom: 24px;
}
.result-formula {
  background: rgba(255,255,255,0.15);
  padding: 16px;
  border-radius: 12px;
  font-family: 'Courier New', monospace;
  font-size: 14px;
  margin-top: 16px;
  backdrop-filter: blur(10px);
}
.download-btn {
  margin-top: 20px;
  padding: 12px 24px;
  background: white;
  color: #667eea;
  border: none;
  border-radius: 12px;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.3s ease;
  font-size: 16px;
}
.download-btn:hover {
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(255,255,255,0.3);
}

/* 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: 40px auto 80px;
  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: 8px;
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}
.meta-line {
  font-size: 14px;
  color: #718096;
  margin-bottom: 28px;
}
.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 a {
  color: #4f46e5;
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}
.blog-content a:hover {
  color: #3730a3;
}
.blog-content strong { color: #667eea; font-weight: 700; }
.blog-content em { font-style: italic; color: #764ba2; }
.highlight-box {
  background: linear-gradient(135deg, #f0f4ff 0%, #e9d5ff 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 Section */
.faq-section {
  max-width: 900px;
  margin: 0 auto 80px;
  padding: 0 20px;
}
.faq-card {
  background: white;
  border-radius: 24px;
  padding: 40px 40px 32px;
  box-shadow: 0 10px 40px rgba(0,0,0,0.08);
}
.faq-card h2 {
  font-size: 32px;
  font-weight: 800;
  margin-bottom: 24px;
  color: #1a202c;
}
.faq-item + .faq-item {
  border-top: 1px solid #e2e8f0;
  margin-top: 16px;
  padding-top: 16px;
}
.faq-question {
  font-weight: 600;
  color: #2d3748;
  margin-bottom: 6px;
}
.faq-answer {
  color: #4a5568;
  font-size: 15px;
  line-height: 1.8;
}

/* Footer */
.footer {
  background: linear-gradient(135deg, #2d3748 0%, #1a202c 100%);
  color: white;
  padding: 60px 0 20px;
  margin-top: 40px;
}
.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;
}

/* Responsive */
@media (max-width: 768px) {
  /* hide desktop navs on mobile */
  .main-nav,
  .more-nav {
    display: none;
  }

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

  .page-header h1 {
    font-size: 36px;
  }
  .page-header p {
    font-size: 18px;
  }
  .calculator-card {
    padding: 24px;
  }
  .result-value {
    font-size: 42px;
  }
  .blog-content {
    padding: 32px 24px;
  }
  .blog-content h2 {
    font-size: 32px;
  }
  .blog-content h3 {
    font-size: 24px;
  }
  .tab-navigation {
    gap: 8px;
  }
  .tab-btn {
    padding: 10px 16px;
    font-size: 14px;
  }
}

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