/* ==========================================================================
   HYPERCALC.NET - Core Design System & Global Stylesheet
   Ultra-fast, accessible, modern responsive styling with Light/Dark support
   ========================================================================== */

:root {
  /* Color Palette - Light Mode Default */
  --bg-primary: #f8fafc;
  --bg-surface: #ffffff;
  --bg-surface-alt: #f1f5f9;
  --bg-card: #ffffff;
  --border-color: #e2e8f0;
  --border-subtle: #f1f5f9;

  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-muted: #94a3b8;
  --text-inverse: #ffffff;

  /* Brand Accents */
  --primary: #4f46e5;
  --primary-hover: #4338ca;
  --primary-light: #eef2ff;
  --primary-glow: rgba(79, 70, 229, 0.15);

  --accent-cyan: #06b6d4;
  --accent-cyan-light: #ecfeff;
  --accent-emerald: #10b981;
  --accent-emerald-light: #ecfdf5;
  --accent-amber: #f59e0b;
  --accent-amber-light: #fffbeb;
  --accent-rose: #f43f5e;
  --accent-rose-light: #fff1f2;

  /* Elevations & Shadows */
  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.07), 0 2px 4px -2px rgba(0, 0, 0, 0.05);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.08), 0 4px 6px -4px rgba(0, 0, 0, 0.04);
  --shadow-glow: 0 0 20px rgba(79, 70, 229, 0.2);

  /* Typography & Layout */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", monospace;
  --max-w-content: 1200px;
  --max-w-reading: 820px;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --radius-full: 9999px;
  --transition: all 0.2s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Ad Placement Containers */
.ad-slot-wrapper {
  width: 100%;
  max-width: 100%;
  margin: 1.75rem auto;
  text-align: center;
  overflow: hidden;
  clear: both;
}

.ad-slot-wrapper .ad-notice {
  font-size: 0.6875rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.35rem;
  display: block;
}

.ad-slot-header {
  margin-top: 1.5rem;
  margin-bottom: 2rem;
}

.ad-slot-content {
  margin: 2.5rem 0;
  padding: 1.5rem 0;
  border-top: 1px dashed var(--border-color);
  border-bottom: 1px dashed var(--border-color);
}

/* Dark Mode Theme */
[data-theme="dark"] {
  --bg-primary: #0b0f19;
  --bg-surface: #111827;
  --bg-surface-alt: #1f2937;
  --bg-card: #141c2e;
  --border-color: #232f48;
  --border-subtle: #1e293b;

  --text-primary: #f8fafc;
  --text-secondary: #94a3b8;
  --text-muted: #64748b;
  --text-inverse: #0b0f19;

  --primary: #6366f1;
  --primary-hover: #818cf8;
  --primary-light: rgba(99, 102, 241, 0.15);
  --primary-glow: rgba(99, 102, 241, 0.3);

  --accent-cyan-light: rgba(6, 182, 212, 0.15);
  --accent-emerald-light: rgba(16, 185, 129, 0.15);
  --accent-amber-light: rgba(245, 158, 11, 0.15);
  --accent-rose-light: rgba(244, 63, 94, 0.15);

  --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.3);
  --shadow-md: 0 4px 10px rgba(0, 0, 0, 0.4);
  --shadow-lg: 0 12px 24px -4px rgba(0, 0, 0, 0.5);
  --shadow-glow: 0 0 25px rgba(99, 102, 241, 0.35);
}

/* Reset & Base Setup */
*, *::before, *::after {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  font-family: var(--font-sans);
  font-size: 16px;
  line-height: 1.6;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  background-color: var(--bg-primary);
  color: var(--text-primary);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  transition: background-color 0.25s ease, color 0.25s ease;
}

a {
  color: var(--primary);
  text-decoration: none;
  transition: var(--transition);
}

a:hover {
  text-decoration: none;
  opacity: 0.9;
}

img, svg {
  max-width: 100%;
  height: auto;
  display: block;
}

input, button, select, textarea {
  font-family: inherit;
  font-size: inherit;
}

.container {
  width: 100%;
  max-width: var(--max-w-content);
  margin: 0 auto;
  padding: 0 1.25rem;
}

.container-narrow {
  width: 100%;
  max-width: var(--max-w-reading);
  margin: 0 auto;
  padding: 0 1.25rem;
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  transition: var(--transition);
}

[data-theme="dark"] .site-header {
  background: rgba(17, 24, 39, 0.85);
}

.nav-container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 4rem;
}

.brand-logo {
  display: flex;
  align-items: center;
  gap: 0.625rem;
  font-weight: 800;
  font-size: 1.25rem;
  color: var(--text-primary);
  letter-spacing: -0.025em;
}

.brand-logo .brand-icon {
  width: 34px;
  height: 34px;
  border-radius: var(--radius-sm);
  background: linear-gradient(135deg, #4f46e5, #06b6d4);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #ffffff;
}

.brand-logo span.dot-net {
  color: var(--primary);
}

.nav-links {
  display: flex;
  align-items: center;
  gap: 1.5rem;
  list-style: none;
}

.nav-links a {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  font-weight: 500;
  padding: 0.5rem 0.25rem;
}

.nav-links a:hover,
.nav-links a.active {
  color: var(--primary);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.theme-toggle-btn {
  background: var(--bg-surface-alt);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  width: 2.375rem;
  height: 2.375rem;
  border-radius: var(--radius-md);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: var(--transition);
}

.theme-toggle-btn:hover {
  color: var(--primary);
  border-color: var(--primary);
}

.mobile-menu-btn {
  display: none;
  background: none;
  border: none;
  color: var(--text-primary);
  cursor: pointer;
  padding: 0.5rem;
}

/* ==========================================================================
   Hero Section
   ========================================================================== */
.hero-section {
  padding: 3.5rem 0 2.5rem;
  text-align: center;
  position: relative;
  overflow: hidden;
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.85rem;
  background: var(--primary-light);
  color: var(--primary);
  border-radius: var(--radius-full);
  font-size: 0.8125rem;
  font-weight: 600;
  margin-bottom: 1.25rem;
  border: 1px solid var(--primary-glow);
}

.hero-title {
  font-size: clamp(2.2rem, 5vw, 3.4rem);
  font-weight: 800;
  line-height: 1.15;
  letter-spacing: -0.035em;
  color: var(--text-primary);
  margin-bottom: 1rem;
}

.hero-title .gradient-text {
  background: linear-gradient(135deg, #4f46e5 0%, #06b6d4 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
}

.hero-description {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 650px;
  margin: 0 auto 2rem;
  line-height: 1.6;
}

/* Live Search Bar */
.search-container {
  max-width: 580px;
  margin: 0 auto 2.5rem;
  position: relative;
}

.search-input-wrapper {
  position: relative;
  display: flex;
  align-items: center;
}

.search-input-wrapper svg {
  position: absolute;
  left: 1.25rem;
  color: var(--text-muted);
  pointer-events: none;
}

.search-input {
  width: 100%;
  padding: 1rem 1rem 1rem 3.25rem;
  font-size: 1rem;
  border-radius: var(--radius-lg);
  border: 2px solid var(--border-color);
  background: var(--bg-surface);
  color: var(--text-primary);
  box-shadow: var(--shadow-md);
  transition: var(--transition);
  outline: none;
}

.search-input:focus {
  border-color: var(--primary);
  box-shadow: var(--shadow-glow);
}

.quick-filter-tags {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 0.875rem;
}

.filter-tag {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  color: var(--text-secondary);
  padding: 0.35rem 0.85rem;
  border-radius: var(--radius-full);
  font-size: 0.8125rem;
  font-weight: 500;
  cursor: pointer;
  transition: var(--transition);
}

.filter-tag:hover,
.filter-tag.active {
  background: var(--primary);
  color: #ffffff;
  border-color: var(--primary);
}

/* ==========================================================================
   Calculator Grid & Cards
   ========================================================================== */
.section-header {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  margin-bottom: 2rem;
  flex-wrap: wrap;
  gap: 1rem;
}

.section-title {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}

.section-subtitle {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  margin-top: 0.25rem;
}

.calc-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
  gap: 1.5rem;
  margin-bottom: 4rem;
}

.calc-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  box-shadow: var(--shadow-sm);
  transition: var(--transition);
  position: relative;
  text-decoration: none;
}

.calc-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--primary);
}

.card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-bottom: 1rem;
}

.card-icon {
  width: 44px;
  height: 44px;
  border-radius: var(--radius-md);
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
}

.icon-finance { background: var(--primary-light); color: var(--primary); }
.icon-health { background: var(--accent-emerald-light); color: var(--accent-emerald); }
.icon-math { background: var(--accent-cyan-light); color: var(--accent-cyan); }
.icon-utility { background: var(--accent-amber-light); color: var(--accent-amber); }

.card-tag {
  font-size: 0.6875rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: 0.25rem 0.55rem;
  border-radius: var(--radius-sm);
}

.tag-finance { background: var(--primary-light); color: var(--primary); }
.tag-health { background: var(--accent-emerald-light); color: var(--accent-emerald); }
.tag-math { background: var(--accent-cyan-light); color: var(--accent-cyan); }
.tag-utility { background: var(--accent-amber-light); color: var(--accent-amber); }

.card-title {
  font-size: 1.1875rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.5rem;
}

.card-desc {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.5;
  flex-grow: 1;
  margin-bottom: 1.25rem;
}

.card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.875rem;
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--primary);
}

.card-footer svg {
  transition: transform 0.2s ease;
}

.calc-card:hover .card-footer svg {
  transform: translateX(4px);
}

/* ==========================================================================
   Featured Visual Banner
   ========================================================================== */
.feature-banner {
  background: var(--bg-surface);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  margin: 3rem 0 4rem;
  display: grid;
  grid-template-columns: 1.2fr 1fr;
  align-items: center;
  box-shadow: var(--shadow-md);
}

.banner-content {
  padding: 3rem;
}

.banner-content h3 {
  font-size: 1.875rem;
  font-weight: 800;
  line-height: 1.2;
  margin-bottom: 1rem;
}

.banner-content p {
  color: var(--text-secondary);
  margin-bottom: 1.75rem;
  font-size: 1rem;
}

.banner-image {
  height: 100%;
  min-height: 280px;
}

.banner-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

/* ==========================================================================
   Article Grid & Cards
   ========================================================================== */
.article-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(340px, 1fr));
  gap: 1.75rem;
  margin-bottom: 4rem;
}

.article-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-lg);
  overflow: hidden;
  display: flex;
  flex-direction: column;
  transition: var(--transition);
  box-shadow: var(--shadow-sm);
  text-decoration: none;
}

.article-card:hover {
  transform: translateY(-4px);
  border-color: var(--primary);
  box-shadow: var(--shadow-lg);
}

.article-card-body {
  padding: 1.5rem;
  display: flex;
  flex-direction: column;
  flex-grow: 1;
}

.article-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.75rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

.article-card-title {
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: 0.625rem;
  line-height: 1.4;
}

.article-card-snippet {
  font-size: 0.875rem;
  color: var(--text-secondary);
  line-height: 1.55;
  margin-bottom: 1.25rem;
  flex-grow: 1;
}

.article-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-top: 1px solid var(--border-subtle);
  padding-top: 0.875rem;
  font-size: 0.8125rem;
  color: var(--text-secondary);
}

.reading-time {
  display: flex;
  align-items: center;
  gap: 0.35rem;
}

/* ==========================================================================
   Article Detail Page Layout
   ========================================================================== */
.article-header {
  padding: 2.5rem 0 2rem;
  text-align: left;
}

.breadcrumbs {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-size: 0.8125rem;
  color: var(--text-muted);
  margin-bottom: 1.25rem;
  flex-wrap: wrap;
}

.breadcrumbs a {
  color: var(--text-secondary);
}

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

.article-title-main {
  font-size: clamp(2rem, 4vw, 2.75rem);
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: -0.03em;
  margin-bottom: 1.25rem;
  color: var(--text-primary);
}

.article-header-meta {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 1.25rem;
  font-size: 0.875rem;
  color: var(--text-secondary);
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 1.5rem;
}

.author-info {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 600;
}

.author-avatar {
  width: 28px;
  height: 28px;
  border-radius: var(--radius-full);
  background: var(--primary-light);
  color: var(--primary);
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.75rem;
  font-weight: 700;
}

.article-content {
  font-size: 1.0625rem;
  line-height: 1.8;
  color: var(--text-primary);
  margin-top: 2rem;
  margin-bottom: 4rem;
}

.article-content h2 {
  font-size: 1.625rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin: 2.25rem 0 1rem;
  padding-bottom: 0.5rem;
  border-bottom: 1px solid var(--border-subtle);
}

.article-content h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin: 1.75rem 0 0.75rem;
}

.article-content p {
  margin-bottom: 1.5rem;
}

.article-content ul,
.article-content ol {
  margin-bottom: 1.5rem;
  padding-left: 1.5rem;
}

.article-content li {
  margin-bottom: 0.5rem;
}

.article-content blockquote {
  border-left: 4px solid var(--primary);
  padding: 1rem 1.25rem;
  background: var(--primary-light);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  margin: 1.75rem 0;
  font-style: italic;
  color: var(--text-primary);
}

.data-table-container {
  overflow-x: auto;
  margin: 2rem 0;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}

.article-content table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.9375rem;
}

.article-content th {
  background: var(--bg-surface-alt);
  padding: 0.875rem 1rem;
  font-weight: 600;
  border-bottom: 2px solid var(--border-color);
}

.article-content td {
  padding: 0.875rem 1rem;
  border-bottom: 1px solid var(--border-color);
}

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

.calculator-callout {
  background: var(--bg-surface);
  border: 2px solid var(--primary);
  border-radius: var(--radius-lg);
  padding: 1.75rem;
  margin: 2.5rem 0;
  box-shadow: var(--shadow-md);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
  flex-wrap: wrap;
}

.calculator-callout-text h4 {
  font-size: 1.25rem;
  font-weight: 700;
  margin-bottom: 0.35rem;
}

.calculator-callout-text p {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  margin-bottom: 0;
}

/* ==========================================================================
   Buttons & UI Elements
   ========================================================================== */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  padding: 0.75rem 1.35rem;
  font-size: 0.9375rem;
  font-weight: 600;
  border-radius: var(--radius-md);
  cursor: pointer;
  transition: var(--transition);
  border: 1px solid transparent;
  text-decoration: none;
}

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

.btn-primary:hover {
  background: var(--primary-hover);
  box-shadow: 0 4px 12px var(--primary-glow);
  color: #ffffff;
}

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

.btn-secondary:hover {
  background: var(--bg-surface-alt);
  border-color: var(--text-muted);
}

/* ==========================================================================
   Footer
   ========================================================================== */
.site-footer {
  margin-top: auto;
  background: var(--bg-surface);
  border-top: 1px solid var(--border-color);
  padding: 4rem 0 2rem;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr repeat(3, 1fr);
  gap: 2.5rem;
  margin-bottom: 3rem;
}

.footer-brand p {
  color: var(--text-secondary);
  font-size: 0.9375rem;
  margin-top: 0.875rem;
  max-width: 320px;
}

.footer-col h5 {
  font-size: 0.9375rem;
  font-weight: 700;
  margin-bottom: 1.125rem;
  color: var(--text-primary);
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.625rem;
}

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

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

.footer-bottom {
  padding-top: 2rem;
  border-top: 1px solid var(--border-subtle);
  display: flex;
  align-items: center;
  justify-content: space-between;
  font-size: 0.8125rem;
  color: var(--text-muted);
  flex-wrap: wrap;
  gap: 1rem;
}

/* ==========================================================================
   Responsive Breakpoints
   ========================================================================== */
@media (max-width: 900px) {
  .feature-banner {
    grid-template-columns: 1fr;
  }
  .banner-image {
    max-height: 260px;
  }
  .footer-grid {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 768px) {
  .nav-links {
    display: none;
  }
  .mobile-menu-btn {
    display: block;
  }
  .nav-links.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 4rem;
    left: 0;
    width: 100%;
    background: var(--bg-surface);
    padding: 1.5rem;
    border-bottom: 1px solid var(--border-color);
    box-shadow: var(--shadow-lg);
  }
  .calc-grid, .article-grid {
    grid-template-columns: 1fr;
  }
  .footer-grid {
    grid-template-columns: 1fr;
  }
}