:root {
  --color-primary: #2563eb;
  --color-primary-dark: #1d4ed8;
  --color-secondary: #64748b;
  --color-success: #22c55e;
  --color-warning: #f59e0b;
  --color-danger: #ef4444;
  --color-bg: #ffffff;
  --color-bg-secondary: #f8fafc;
  --color-bg-card: #ffffff;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;
  
  --spacing-xs: 0.25rem;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2rem;
  --spacing-2xl: 3rem;
  
  --breakpoint-sm: 640px;
  --breakpoint-md: 768px;
  --breakpoint-lg: 1024px;
  --breakpoint-xl: 1280px;
  
  --radius-sm: 0.375rem;
  --radius-md: 0.5rem;
  --radius-lg: 0.75rem;
  --radius-xl: 1rem;
  
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
  
  --font-sans: 'Inter', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', monospace;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  font-size: 1rem;
}

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

.header {
  background-color: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  box-shadow: var(--shadow-sm);
}

.header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md);
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  text-decoration: none;
  color: var(--color-text);
  font-weight: 700;
  font-size: 1.25rem;
}

.logo-icon {
  font-size: 1.5rem;
}

.logo-text {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.nav {
  display: flex;
  align-items: center;
}

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

.nav-list a {
  text-decoration: none;
  color: var(--color-text-secondary);
  font-weight: 500;
  padding: var(--spacing-sm) var(--spacing-md);
  border-radius: var(--radius-md);
  transition: all 0.2s ease;
}

.nav-list a:hover {
  color: var(--color-primary);
  background-color: var(--color-bg-secondary);
}

.mobile-menu-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--spacing-sm);
}

.mobile-menu-toggle span {
  width: 24px;
  height: 2px;
  background-color: var(--color-text);
  border-radius: 2px;
}

.main {
  padding: var(--spacing-2xl) 0;
}

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

.article h1 {
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--color-text);
  margin-bottom: var(--spacing-lg);
  line-height: 1.2;
}

.article h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  margin-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-lg);
}

.article h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text);
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
}

.article p {
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-lg);
  font-size: 1.05rem;
  line-height: 1.8;
}

.article ul,
.article ol {
  color: var(--color-text-secondary);
  margin-bottom: var(--spacing-lg);
  padding-left: var(--spacing-xl);
}

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

.article a {
  color: var(--color-primary);
  text-decoration: none;
  font-weight: 500;
  border-bottom: 2px solid transparent;
  transition: border-color 0.2s ease;
}

.article a:hover {
  border-bottom-color: var(--color-primary);
}

.intro {
  font-size: 1.125rem;
  color: var(--color-text);
  font-weight: 500;
}

.ad-slot {
  display: flex;
  justify-content: center;
  margin: var(--spacing-xl) 0;
}

.ad-slot-a {
  margin-bottom: var(--spacing-2xl);
}

.ad-slot-b {
  margin: var(--spacing-2xl) 0;
}

.ad-slot-c {
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-lg);
}

.calculator {
  background-color: var(--color-bg-card);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-lg);
  overflow: hidden;
  margin: var(--spacing-2xl) 0;
}

.calculator-header {
  background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
  padding: var(--spacing-xl);
  text-align: center;
}

.calculator-header h2 {
  color: white;
  margin: 0;
  font-size: 1.5rem;
  font-weight: 600;
}

.calculator-form {
  padding: var(--spacing-xl);
}

.form-group {
  margin-bottom: var(--spacing-lg);
}

.form-group label {
  display: block;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
  font-size: 0.9rem;
}

.form-input {
  width: 100%;
  padding: var(--spacing-md);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: 1.125rem;
  font-family: var(--font-mono);
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
  background-color: var(--color-bg);
}

.form-input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1);
}

.form-input::placeholder {
  color: var(--color-text-secondary);
}

.input-unit {
  display: inline-block;
  margin-left: var(--spacing-sm);
  color: var(--color-text-secondary);
  font-size: 0.9rem;
}

.form-row {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
  gap: var(--spacing-lg);
}

.form-checkbox-group {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.form-checkbox {
  width: 1.25rem;
  height: 1.25rem;
  accent-color: var(--color-primary);
}

.form-select {
  width: 100%;
  padding: var(--spacing-md);
  border: 2px solid var(--color-border);
  border-radius: var(--radius-md);
  font-size: 1rem;
  background-color: var(--color-bg);
  color: var(--color-text);
  cursor: pointer;
  transition: border-color 0.2s ease;
}

.form-select:focus {
  outline: none;
  border-color: var(--color-primary);
}

.calculator-results {
  background-color: var(--color-bg-secondary);
  padding: var(--spacing-xl);
  border-top: 1px solid var(--color-border);
}

.result-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-md) 0;
  border-bottom: 1px solid var(--color-border-light);
}

.result-item:last-child {
  border-bottom: none;
}

.result-label {
  font-weight: 500;
  color: var(--color-text-secondary);
}

.result-value {
  font-weight: 700;
  color: var(--color-primary);
  font-family: var(--font-mono);
  font-size: 1.25rem;
}

.result-value--success {
  color: var(--color-success);
}

.result-value--warning {
  color: var(--color-warning);
}

.result-value--danger {
  color: var(--color-danger);
}

.result-section {
  margin-bottom: var(--spacing-lg);
}

.result-section-title {
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-md);
  font-size: 1.125rem;
}

.disclaimer {
  background-color: #fffbeb;
  border-left: 4px solid var(--color-warning);
  padding: var(--spacing-lg);
  margin-top: var(--spacing-2xl);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
}

.disclaimer p {
  margin: 0;
  color: var(--color-text);
  font-size: 0.9rem;
  line-height: 1.6;
}

.disclaimer strong {
  color: var(--color-warning);
}

.footer {
  background-color: var(--color-bg-secondary);
  border-top: 1px solid var(--color-border);
  padding: var(--spacing-2xl) 0 var(--spacing-lg);
}

.footer .container {
  text-align: center;
}

.footer-links {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

.footer-links a {
  text-decoration: none;
  color: var(--color-text-secondary);
  font-size: 0.9rem;
  transition: color 0.2s ease;
}

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

.footer-copyright {
  color: var(--color-text-secondary);
  font-size: 0.875rem;
}

.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: var(--spacing-lg);
  margin-top: var(--spacing-xl);
}

.card {
  background-color: var(--color-bg-card);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-md);
  overflow: hidden;
  text-decoration: none;
  color: inherit;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-xl);
}

.card-icon {
  font-size: 3rem;
  padding: var(--spacing-xl);
  text-align: center;
  background: linear-gradient(135deg, rgba(37, 99, 235, 0.1), rgba(37, 99, 235, 0.05));
}

.card-content {
  padding: var(--spacing-lg);
}

.card-title {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
}

.card-description {
  color: var(--color-text-secondary);
  font-size: 0.9rem;
  line-height: 1.6;
}

.card-tag {
  display: inline-block;
  background-color: var(--color-primary);
  color: white;
  font-size: 0.75rem;
  font-weight: 500;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  margin-top: var(--spacing-sm);
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: var(--spacing-md) var(--spacing-xl);
  border: none;
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 1rem;
  cursor: pointer;
  transition: all 0.2s ease;
  text-decoration: none;
}

.btn--primary {
  background-color: var(--color-primary);
  color: white;
}

.btn--primary:hover {
  background-color: var(--color-primary-dark);
  transform: translateY(-1px);
  box-shadow: var(--shadow-md);
}

.btn--secondary {
  background-color: var(--color-bg-secondary);
  color: var(--color-text);
}

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

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

.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-size: 0.75rem;
  font-weight: 600;
}

.badge--success {
  background-color: rgba(34, 197, 94, 0.1);
  color: var(--color-success);
}

.badge--warning {
  background-color: rgba(245, 158, 11, 0.1);
  color: var(--color-warning);
}

.badge--info {
  background-color: rgba(37, 99, 235, 0.1);
  color: var(--color-primary);
}

.table {
  width: 100%;
  border-collapse: collapse;
  margin-bottom: var(--spacing-lg);
  background-color: var(--color-bg-card);
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-sm);
}

.table th,
.table td {
  padding: var(--spacing-md);
  text-align: left;
  border-bottom: 1px solid var(--color-border-light);
}

.table th {
  background-color: var(--color-bg-secondary);
  font-weight: 600;
  color: var(--color-text);
}

.table tr:hover {
  background-color: var(--color-bg-secondary);
}

.table tr:last-child td {
  border-bottom: none;
}

.faq-item {
  margin-bottom: var(--spacing-md);
}

.faq-question {
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
}

.faq-question::before {
  content: 'Q:';
  color: var(--color-primary);
  font-weight: 700;
}

.faq-answer {
  color: var(--color-text-secondary);
  padding-left: 2rem;
  line-height: 1.8;
}

.faq-answer::before {
  content: 'A:';
  color: var(--color-success);
  font-weight: 600;
  margin-right: var(--spacing-sm);
}

.alert {
  padding: var(--spacing-lg);
  border-radius: var(--radius-md);
  margin-bottom: var(--spacing-lg);
}

.alert--info {
  background-color: rgba(37, 99, 235, 0.1);
  color: var(--color-primary);
}

.alert--warning {
  background-color: rgba(245, 158, 11, 0.1);
  color: var(--color-warning);
}

.alert--error {
  background-color: rgba(239, 68, 68, 0.1);
  color: var(--color-danger);
}

.alert--success {
  background-color: rgba(34, 197, 94, 0.1);
  color: var(--color-success);
}

@media (max-width: 768px) {
  .nav {
    display: none;
  }
  
  .nav.active {
    display: flex;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    background-color: var(--color-bg);
    border-bottom: 1px solid var(--color-border);
    padding: var(--spacing-md);
  }
  
  .nav-list {
    flex-direction: column;
    gap: 0;
    width: 100%;
  }
  
  .nav-list li {
    margin: var(--spacing-sm) 0;
  }
  
  .nav-list a {
    display: block;
    padding: var(--spacing-md);
  }
  
  .mobile-menu-toggle {
    display: flex;
  }
  
  .article h1 {
    font-size: 1.75rem;
  }
  
  .article h2 {
    font-size: 1.25rem;
  }
  
  .form-row {
    grid-template-columns: 1fr;
  }
  
  .card-grid {
    grid-template-columns: 1fr;
  }
  
  .footer-links {
    flex-direction: column;
    gap: var(--spacing-md);
  }
  
  .table {
    display: block;
    overflow-x: auto;
  }
}

@media (max-width: 640px) {
  .container {
    padding: 0 var(--spacing-sm);
  }
  
  .main {
    padding: var(--spacing-xl) 0;
  }
  
  .calculator-form {
    padding: var(--spacing-lg);
  }
  
  .calculator-results {
    padding: var(--spacing-lg);
  }
}