/* ── Base Reset & Typography ─────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { -webkit-text-size-adjust: 100%; line-height: 1.5; tab-size: 4; }
body { font-family: 'Inter', ui-sans-serif, system-ui, -apple-system, sans-serif; line-height: 1.6; }

/* ── Tailwind-like Utility Classes ──────────────────── */
/* Layout */
.mx-auto { margin-left: auto; margin-right: auto; }
.max-w-7xl { max-width: 80rem; }
.max-w-4xl { max-width: 56rem; }
.max-w-3xl { max-width: 48rem; }
.max-w-md { max-width: 28rem; }
.min-h-screen { min-height: 100vh; }
.relative { position: relative; }
.overflow-hidden { overflow: hidden; }
.block { display: block; }
.inline-flex { display: inline-flex; }
.flex { display: flex; }
.hidden { display: none; }
.grid { display: grid; }
.items-center { align-items: center; }
.justify-center { justify-content: center; }
.justify-between { justify-content: space-between; }
.flex-col { flex-direction: column; }
.gap-2 { gap: 0.5rem; }
.gap-4 { gap: 1rem; }
.gap-6 { gap: 1.5rem; }
.gap-8 { gap: 2rem; }
.space-x-1 > * + * { margin-left: 0.25rem; }
.space-x-3 > * + * { margin-left: 0.75rem; }
.space-x-6 > * + * { margin-left: 1.5rem; }
.space-y-1 > * + * { margin-top: 0.25rem; }
.space-y-3 > * + * { margin-top: 0.75rem; }
.space-y-4 > * + * { margin-top: 1rem; }
.space-y-6 > * + * { margin-top: 1.5rem; }

/* Grid columns */
.grid-cols-1 { grid-template-columns: repeat(1, minmax(0, 1fr)); }
.col-span-1 { grid-column: span 1 / span 1; }

/* Spacing */
.p-2 { padding: 0.5rem; }
.p-3 { padding: 0.75rem; }
.p-4 { padding: 1rem; }
.p-5 { padding: 1.25rem; }
.p-6 { padding: 1.5rem; }
.p-8 { padding: 2rem; }
.px-2 { padding-left: 0.5rem; padding-right: 0.5rem; }
.px-3 { padding-left: 0.75rem; padding-right: 0.75rem; }
.px-4 { padding-left: 1rem; padding-right: 1rem; }
.px-6 { padding-left: 1.5rem; padding-right: 1.5rem; }
.py-2 { padding-top: 0.5rem; padding-bottom: 0.5rem; }
.py-3 { padding-top: 0.75rem; padding-bottom: 0.75rem; }
.py-4 { padding-top: 1rem; padding-bottom: 1rem; }
.py-12 { padding-top: 3rem; padding-bottom: 3rem; }
.py-16 { padding-top: 4rem; padding-bottom: 4rem; }
.pt-2 { padding-top: 0.5rem; }
.pt-8 { padding-top: 2rem; }
.pb-3 { padding-bottom: 0.75rem; }
.mt-1 { margin-top: 0.25rem; }
.mt-4 { margin-top: 1rem; }
.mt-8 { margin-top: 2rem; }
.mb-1 { margin-bottom: 0.25rem; }
.mb-2 { margin-bottom: 0.5rem; }
.mb-4 { margin-bottom: 1rem; }
.mb-6 { margin-bottom: 1.5rem; }
.mb-8 { margin-bottom: 2rem; }
.mb-12 { margin-bottom: 3rem; }
.mb-16 { margin-bottom: 4rem; }
.ml-1 { margin-left: 0.25rem; }
.ml-2 { margin-left: 0.5rem; }
.ml-4 { margin-left: 1rem; }
.mr-1 { margin-right: 0.25rem; }

/* Typography */
.text-xs { font-size: 0.75rem; line-height: 1rem; }
.text-sm { font-size: 0.875rem; line-height: 1.25rem; }
.text-base { font-size: 1rem; line-height: 1.5rem; }
.text-lg { font-size: 1.125rem; line-height: 1.75rem; }
.text-xl { font-size: 1.25rem; line-height: 1.75rem; }
.text-2xl { font-size: 1.5rem; line-height: 2rem; }
.text-3xl { font-size: 1.875rem; line-height: 2.25rem; }
.text-4xl { font-size: 2.25rem; line-height: 2.5rem; }
.font-medium { font-weight: 500; }
.font-semibold { font-weight: 600; }
.font-bold { font-weight: 700; }
.tracking-tight { letter-spacing: -0.025em; }
.tracking-wider { letter-spacing: 0.05em; }
.uppercase { text-transform: uppercase; }
.text-center { text-align: center; }
.antialiased { -webkit-font-smoothing: antialiased; -moz-osx-font-smoothing: grayscale; }
.font-sans { font-family: 'Inter', ui-sans-serif, system-ui, -apple-system, sans-serif; }
.font-mono { font-family: ui-monospace, SFMono-Regular, 'SF Mono', Menlo, Consolas, monospace; }
.line-clamp-2 { display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
.line-clamp-3 { display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow: hidden; }

/* Colors */
.text-white { color: #fff; }
.text-gray-400 { color: #9ca3af; }
.text-gray-500 { color: #6b7280; }
.text-gray-600 { color: #4b5563; }
.text-gray-700 { color: #374151; }
.text-gray-900 { color: #111827; }
.text-blue-600 { color: #2563eb; }
.text-green-600 { color: #16a34a; }
.text-purple-600 { color: #9333ea; }
.text-amber-600 { color: #d97706; }
.text-red-600 { color: #dc2626; }
.bg-white { background-color: #fff; }
.bg-gray-50 { background-color: #f9fafb; }
.bg-blue-50 { background-color: #eff6ff; }
.bg-blue-100 { background-color: #dbeafe; }
.bg-blue-600 { background-color: #2563eb; }
.bg-green-100 { background-color: #dcfce7; }
.bg-purple-100 { background-color: #f3e8ff; }
.bg-amber-100 { background-color: #fef3c7; }
.bg-red-50 { background-color: #fef2f2; }
.bg-green-50 { background-color: #f0fdf4; }

/* Borders */
.border-t { border-top: 1px solid; }
.border-b { border-bottom: 1px solid; }
.border { border: 1px solid; }
.border-transparent { border-color: transparent; }
.border-gray-200 { border-color: #e5e7eb; }
.border-gray-300 { border-color: #d1d5db; }
.rounded-md { border-radius: 0.375rem; }
.rounded-lg { border-radius: 0.5rem; }
.rounded-xl { border-radius: 0.75rem; }
.rounded-2xl { border-radius: 1rem; }

/* Shadows & Rings */
.shadow-sm { box-shadow: 0 1px 2px 0 rgb(0 0 0 / 0.05); }
.shadow-md { box-shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1); }
.shadow-lg { box-shadow: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1); }
.ring-1 { box-shadow: 0 0 0 1px var(--ring-color, #e5e7eb); }
.ring-gray-200 { --ring-color: #e5e7eb; }

/* Transitions */
.transition-all { transition: all 0.2s ease; }
.transition-colors { transition: color 0.2s ease, background-color 0.2s ease, border-color 0.2s ease; }
.duration-200 { transition-duration: 200ms; }

/* Sizing */
.h-6 { height: 1.5rem; }
.h-8 { height: 2rem; }
.h-12 { height: 3rem; }
.h-16 { height: 4rem; }
.w-3 { width: 0.75rem; }
.w-6 { width: 1.5rem; }
.w-8 { width: 2rem; }
.w-12 { width: 3rem; }
.w-full { width: 100%; }

/* Accessibility */
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border-width: 0; }

/* ── Hover States ───────────────────────────────────── */
a:hover { text-decoration: none; }
.hover\:text-blue-600:hover { color: #2563eb; }
.hover\:bg-gray-50:hover { background-color: #f9fafb; }
.hover\:bg-gray-100:hover { background-color: #f3f4f6; }
.hover\:bg-blue-50:hover { background-color: #eff6ff; }
.hover\:bg-blue-700:hover { background-color: #1d4ed8; }
.hover\:text-gray-600:hover { color: #4b5563; }
.hover\:shadow-lg:hover { box-shadow: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1); }
.hover\:shadow-md:hover { box-shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1); }
.hover\:ring-blue-300:hover { --ring-color: #93c5fd; box-shadow: 0 0 0 1px var(--ring-color); }
.hover\:ring-blue-200:hover { --ring-color: #bfdbfe; }
.hover\:ring-1:hover { box-shadow: 0 0 0 1px var(--ring-color, #e5e7eb); }

/* ── Prose (Article Content) ────────────────────────── */
.prose { max-width: 65ch; color: #374151; }
.prose h2 { font-size: 1.5rem; font-weight: 700; color: #111827; margin-top: 2rem; margin-bottom: 1rem; line-height: 1.3; }
.prose h3 { font-size: 1.25rem; font-weight: 600; color: #111827; margin-top: 1.5rem; margin-bottom: 0.75rem; line-height: 1.4; }
.prose h4 { font-size: 1.125rem; font-weight: 600; color: #111827; margin-top: 1.25rem; margin-bottom: 0.5rem; }
.prose p { margin-bottom: 1.25rem; }
.prose ul, .prose ol { padding-left: 1.5rem; margin-bottom: 1.25rem; }
.prose li { margin-bottom: 0.5rem; }
.prose strong { font-weight: 600; color: #111827; }
.prose a { color: #2563eb; text-decoration: underline; }
.prose a:hover { color: #1d4ed8; }
.prose code { font-size: 0.875em; background-color: #f3f4f6; padding: 0.125rem 0.375rem; border-radius: 0.25rem; font-family: ui-monospace, monospace; }
.prose blockquote { border-left: 4px solid #e5e7eb; padding-left: 1rem; color: #6b7280; font-style: italic; margin-bottom: 1.25rem; }
.prose table { width: 100%; border-collapse: collapse; margin-bottom: 1.25rem; }
.prose th, .prose td { border: 1px solid #e5e7eb; padding: 0.5rem 0.75rem; text-align: left; }
.prose th { background-color: #f9fafb; font-weight: 600; }
.prose img { max-width: 100%; height: auto; border-radius: 0.5rem; margin: 1rem 0; }
.prose-lg { font-size: 1.05rem; }
.prose-headings\:text-gray-900 h2, .prose-headings\:text-gray-900 h3, .prose-headings\:text-gray-900 h4 { color: #111827; }
.prose-p\:text-gray-600 p { color: #4b5563; }
.prose-a\:text-blue-600 a { color: #2563eb; }
.prose-strong\:text-gray-900 strong { color: #111827; }
.prose.max-w-none { max-width: none; }

/* ── Form Elements (Calculator Inputs) ──────────────── */
.form-label { display: block; font-size: 0.875rem; font-weight: 600; color: #374151; margin-bottom: 0.375rem; }
.form-input { display: block; width: 100%; padding: 0.5rem 0.75rem; font-size: 1rem; line-height: 1.5; color: #111827; background-color: #fff; border: 1px solid #d1d5db; border-radius: 0.5rem; transition: border-color 0.15s ease, box-shadow 0.15s ease; }
.form-input:focus { outline: none; border-color: #2563eb; box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1); }
.form-input::placeholder { color: #9ca3af; }
.form-select { display: block; width: 100%; padding: 0.5rem 2rem 0.5rem 0.75rem; font-size: 1rem; line-height: 1.5; color: #111827; background-color: #fff; border: 1px solid #d1d5db; border-radius: 0.5rem; appearance: none; background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' fill='none' viewBox='0 0 20 20'%3E%3Cpath stroke='%236b7280' stroke-linecap='round' stroke-linejoin='round' stroke-width='1.5' d='M6 8l4 4 4-4'/%3E%3C/svg%3E"); background-position: right 0.5rem center; background-repeat: no-repeat; background-size: 1.5em 1.5em; }
.form-select:focus { outline: none; border-color: #2563eb; box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.1); }
.form-grid { display: grid; gap: 1rem; }

/* Buttons */
.btn-primary { display: inline-flex; align-items: center; justify-content: center; padding: 0.625rem 1.5rem; font-size: 1rem; font-weight: 600; color: #fff; background-color: #2563eb; border: none; border-radius: 0.5rem; cursor: pointer; transition: background-color 0.15s ease; }
.btn-primary:hover { background-color: #1d4ed8; }
.btn-secondary { display: inline-flex; align-items: center; justify-content: center; padding: 0.5rem 1rem; font-size: 0.875rem; font-weight: 500; color: #374151; background-color: #f3f4f6; border: 1px solid #d1d5db; border-radius: 0.5rem; cursor: pointer; transition: background-color 0.15s ease; }
.btn-secondary:hover { background-color: #e5e7eb; }

/* Result cards */
.result-card { background-color: #f0fdf4; border: 1px solid #bbf7d0; border-radius: 0.75rem; padding: 1.5rem; margin-top: 1.5rem; }
.result-value { font-size: 2rem; font-weight: 700; color: #166534; }
.result-label { font-size: 0.875rem; color: #4b5563; margin-top: 0.25rem; }
.result-row { display: flex; justify-content: space-between; align-items: center; padding: 0.5rem 0; border-bottom: 1px solid #e5e7eb; }
.result-row:last-child { border-bottom: none; }
.error-message { color: #dc2626; font-size: 0.875rem; margin-top: 0.25rem; }

/* ── Responsive ─────────────────────────────────────── */
@media (min-width: 640px) {
  .sm\:px-6 { padding-left: 1.5rem; padding-right: 1.5rem; }
  .sm\:p-8 { padding: 2rem; }
  .sm\:text-5xl { font-size: 3rem; line-height: 1; }
  .sm\:text-6xl { font-size: 3.75rem; line-height: 1; }
  .sm\:py-24 { padding-top: 6rem; padding-bottom: 6rem; }
  .sm\:grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .sm\:grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .form-grid { grid-template-columns: repeat(2, 1fr); }
}

@media (min-width: 768px) {
  .md\:grid-cols-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .md\:grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .md\:grid-cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .md\:col-span-2 { grid-column: span 2 / span 2; }
  .md\:flex-row { flex-direction: row; }
  .md\:items-center { align-items: center; }
  .md\:justify-between { justify-content: space-between; }
  .md\:mt-0 { margin-top: 0; }
  .md\:ml-2 { margin-left: 0.5rem; }
  .md\:space-x-3 > * + * { margin-left: 0.75rem; }
}

@media (min-width: 1024px) {
  .lg\:px-8 { padding-left: 2rem; padding-right: 2rem; }
  .lg\:grid-cols-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
  .lg\:grid-cols-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
}

/* ── Links ──────────────────────────────────────────── */
a { color: inherit; text-decoration: none; }

/* ── See Also Box (for in-content cross-links) ──────── */
.see-also { background-color: #eff6ff; border: 1px solid #bfdbfe; border-radius: 0.5rem; padding: 1rem; margin: 1rem 0; }
.see-also strong { color: #1d4ed8; }