/* ==========================================================================
   AI & DS STUDY HUB - CAL NEWPORT EDITORIAL DESIGN SYSTEM (ENHANCED V2)
   Domain: aidsstudynotes.co.in | Curator: Sarthak Pawar
   ========================================================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&family=Lora:ital,wght@0,400;0,500;0,600;0,700;1,400;1,600&family=JetBrains+Mono:wght@400;500;600&display=swap');

:root {
  --bg-main: #ffffff;
  --bg-subtle: #faf9f6;
  --bg-card: #f8f8f7;
  --text-main: #1f1f1f;
  --text-muted: #4a4a4a;
  --text-light: #6e6e6e;
  --border-color: #e5e5e5;
  --border-dark: #cccccc;
  --accent-burgundy: #9e2a2b;
  --accent-burgundy-hover: #7a1f20;
  --accent-light: #fdf5f5;
  --code-bg: #1e1e24;
  --code-text: #e6edf3;
  --font-editorial: 'Lora', Georgia, Cambria, 'Times New Roman', serif;
  --font-ui: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: 'JetBrains Mono', Consolas, Monaco, monospace;
  --shadow-sm: 0 2px 5px rgba(0,0,0,0.03);
  --shadow-md: 0 6px 16px rgba(0,0,0,0.06);
  --shadow-hover: 0 10px 24px rgba(158, 42, 43, 0.08);
  --radius-sm: 4px;
  --radius-md: 8px;
  --content-max-width: 1160px;
}

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

html {
  font-size: 16px;
  scroll-behavior: smooth;
  background-color: var(--bg-main);
  color: var(--text-main);
}

body {
  font-family: var(--font-editorial);
  line-height: 1.8;
  color: var(--text-main);
  background-color: var(--bg-main);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Top Progress Indicator & Accent Stripe */
.reading-progress-bar {
  position: fixed;
  top: 0;
  left: 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent-burgundy), #d9534f);
  width: 0%;
  z-index: 1000;
  transition: width 0.1s ease;
}

.top-stripe {
  height: 4px;
  background-color: var(--accent-burgundy);
  width: 100%;
}

/* Header & Navigation */
.header-wrapper {
  border-bottom: 1px solid var(--border-color);
  background: rgba(255, 255, 255, 0.96);
  backdrop-filter: blur(8px);
  position: sticky;
  top: 0;
  z-index: 100;
}

.site-header {
  max-width: var(--content-max-width);
  margin: 0 auto;
  padding: 1.15rem 1.5rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.brand-title {
  font-family: var(--font-ui);
  font-weight: 700;
  font-size: 1.3rem;
  letter-spacing: -0.02em;
  color: var(--text-main);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.brand-badge {
  background-color: var(--accent-burgundy);
  color: #ffffff;
  font-size: 0.65rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: 3px;
  letter-spacing: 0.06em;
  text-transform: uppercase;
}

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

.nav-link {
  font-family: var(--font-ui);
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s ease;
  position: relative;
  padding: 0.25rem 0;
}

.nav-link:hover, .nav-link.active {
  color: var(--accent-burgundy);
}

.nav-link.active::after {
  content: '';
  position: absolute;
  bottom: -4px;
  left: 0;
  width: 100%;
  height: 2px;
  background-color: var(--accent-burgundy);
}

/* Page Outer Container */
.page-container {
  max-width: var(--content-max-width);
  margin: 2.5rem auto;
  padding: 0 1.5rem;
}

/* Dual Column Layout */
.layout-grid {
  display: grid;
  grid-template-columns: 2.25fr 0.75fr;
  gap: 3rem;
  align-items: start;
}

.main-content {
  min-width: 0;
}

/* Editorial Article Content */
.article-header {
  margin-bottom: 2.5rem;
  padding-bottom: 1.5rem;
  border-bottom: 1px solid var(--border-color);
}

.article-meta {
  font-family: var(--font-ui);
  font-size: 0.8rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent-burgundy);
  margin-bottom: 0.75rem;
  display: flex;
  align-items: center;
  gap: 0.75rem;
}

.article-meta::after {
  content: '';
  flex-grow: 1;
  height: 1px;
  background-color: var(--border-color);
}

.reading-badge {
  font-family: var(--font-ui);
  font-size: 0.75rem;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 0.15rem 0.5rem;
  border-radius: 12px;
  color: var(--text-light);
  font-weight: 500;
  text-transform: none;
}

.article-title {
  font-family: var(--font-editorial);
  font-size: 2.4rem;
  font-weight: 700;
  line-height: 1.25;
  color: var(--text-main);
  margin-bottom: 0.85rem;
  letter-spacing: -0.015em;
}

.article-subtitle {
  font-family: var(--font-editorial);
  font-size: 1.2rem;
  font-style: italic;
  color: var(--text-muted);
  line-height: 1.5;
}

.lead-paragraph {
  font-size: 1.15rem;
  line-height: 1.85;
  color: #111111;
  margin-bottom: 1.75rem;
  font-weight: 400;
}

.lead-paragraph::first-letter {
  font-size: 3.2rem;
  float: left;
  line-height: 0.8;
  margin-right: 0.6rem;
  margin-top: 0.15rem;
  color: var(--accent-burgundy);
  font-weight: 700;
  font-family: var(--font-editorial);
}

.article-body p {
  margin-bottom: 1.5rem;
  font-size: 1.05rem;
  color: var(--text-main);
}

.article-body h2 {
  font-family: var(--font-editorial);
  font-size: 1.65rem;
  font-weight: 700;
  color: var(--text-main);
  margin: 2.5rem 0 1.1rem 0;
  padding-bottom: 0.4rem;
  border-bottom: 1px solid var(--border-color);
}

.article-body h3 {
  font-family: var(--font-ui);
  font-size: 1.2rem;
  font-weight: 700;
  color: var(--accent-burgundy);
  margin: 2rem 0 0.85rem 0;
}

/* Code Snippets Box */
.code-block-wrapper {
  margin: 1.75rem 0;
  background-color: var(--code-bg);
  border-radius: var(--radius-md);
  overflow: hidden;
  box-shadow: var(--shadow-md);
}

.code-header {
  background: #141419;
  padding: 0.5rem 1rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-family: var(--font-ui);
  font-size: 0.75rem;
  color: #8b949e;
  border-bottom: 1px solid #2d2d35;
}

.code-lang {
  font-weight: 600;
  color: var(--accent-burgundy);
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.code-block {
  padding: 1.25rem;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  line-height: 1.6;
  color: var(--code-text);
  overflow-x: auto;
  white-space: pre;
}

.code-keyword { color: #ff7b72; font-weight: 600; }
.code-func { color: #d2a8ff; }
.code-string { color: #a5d6ff; }
.code-comment { color: #8b949e; font-style: italic; }
.code-num { color: #79c0ff; }

/* Academic Blockquote & Concept Box */
.academic-blockquote {
  margin: 2.25rem 0;
  padding: 1.5rem 2rem;
  background-color: var(--bg-subtle);
  border-left: 4px solid var(--accent-burgundy);
  font-style: italic;
  font-size: 1.08rem;
  color: var(--text-muted);
  border-radius: 0 var(--radius-sm) var(--radius-sm) 0;
}

.academic-blockquote cite {
  display: block;
  font-family: var(--font-ui);
  font-style: normal;
  font-size: 0.85rem;
  font-weight: 700;
  margin-top: 0.85rem;
  color: var(--text-main);
}

.concept-box {
  background-color: var(--accent-light);
  border: 1px solid rgba(158, 42, 43, 0.25);
  border-radius: var(--radius-md);
  padding: 1.75rem;
  margin: 2.25rem 0;
}

.concept-title {
  font-family: var(--font-ui);
  font-size: 0.95rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent-burgundy);
  margin-bottom: 0.85rem;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.concept-list {
  padding-left: 1.25rem;
  color: var(--text-main);
}

.concept-list li {
  margin-bottom: 0.65rem;
  font-size: 0.975rem;
  line-height: 1.6;
}

/* Engineering Tiers Grid (index.html) */
.tiers-section {
  margin-top: 4rem;
  padding-top: 2.5rem;
  border-top: 2px solid var(--text-main);
}

.section-label {
  font-family: var(--font-ui);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent-burgundy);
  margin-bottom: 1.75rem;
}

.tiers-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.5rem;
}

.tier-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.65rem;
  transition: all 0.25 ease;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
}

.tier-card:hover {
  border-color: var(--accent-burgundy);
  transform: translateY(-3px);
  box-shadow: var(--shadow-hover);
}

.tier-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  margin-bottom: 0.75rem;
}

.tier-tag {
  font-family: var(--font-ui);
  font-size: 0.75rem;
  font-weight: 700;
  padding: 0.2rem 0.5rem;
  border-radius: 3px;
  background: #eee;
  color: var(--text-muted);
}

.tier-tag.active-track {
  background: var(--accent-burgundy);
  color: #ffffff;
}

.tier-title {
  font-family: var(--font-ui);
  font-size: 1.15rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.35rem;
}

.tier-session {
  font-family: var(--font-ui);
  font-size: 0.85rem;
  color: var(--text-light);
  margin-bottom: 1rem;
}

.tier-desc {
  font-size: 0.925rem;
  color: var(--text-muted);
  line-height: 1.65;
  margin-bottom: 1.35rem;
  flex-grow: 1;
}

.tier-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.7rem 1.25rem;
  border-radius: var(--radius-sm);
  text-decoration: none;
  transition: all 0.2s ease;
  border: 1px solid var(--accent-burgundy);
  color: var(--accent-burgundy);
  background: transparent;
  width: 100%;
}

.tier-btn:hover {
  background: var(--accent-burgundy);
  color: #ffffff;
}

/* Sidebar Styles */
.sidebar {
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

.sidebar-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 1.75rem;
}

.sidebar-title {
  font-family: var(--font-ui);
  font-size: 0.85rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--text-main);
  margin-bottom: 1.25rem;
  padding-bottom: 0.5rem;
  border-bottom: 2px solid var(--accent-burgundy);
}

.profile-widget {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.25rem;
}

.avatar-circle {
  width: 56px;
  height: 56px;
  border-radius: 50%;
  background-color: var(--accent-burgundy);
  color: #ffffff;
  font-family: var(--font-ui);
  font-weight: 700;
  font-size: 1.25rem;
  display: flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  border: 2px solid #ffffff;
  box-shadow: 0 0 0 2px var(--accent-burgundy);
}

.profile-info h4 {
  font-family: var(--font-ui);
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-main);
}

.profile-info p {
  font-family: var(--font-ui);
  font-size: 0.825rem;
  color: var(--text-muted);
}

.profile-bio {
  font-size: 0.9rem;
  color: var(--text-muted);
  line-height: 1.6;
  margin-bottom: 1.25rem;
}

.sidebar-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.sidebar-links a {
  font-family: var(--font-ui);
  font-size: 0.875rem;
  color: var(--accent-burgundy);
  text-decoration: none;
  font-weight: 500;
  display: flex;
  align-items: center;
  gap: 0.4rem;
}

.sidebar-links a:hover {
  text-decoration: underline;
}

.notice-box {
  background: var(--bg-subtle);
  border: 1px dashed var(--border-dark);
  border-radius: var(--radius-sm);
  padding: 1.15rem;
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.6;
}

/* Interactive Search Bar on FY Page */
.search-wrapper {
  margin: 1.75rem 0 1rem 0;
}

.search-input-box {
  width: 100%;
  padding: 0.85rem 1.25rem;
  font-family: var(--font-ui);
  font-size: 0.95rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  background: var(--bg-card);
  color: var(--text-main);
  transition: all 0.2s ease;
}

.search-input-box:focus {
  outline: none;
  border-color: var(--accent-burgundy);
  background: #ffffff;
  box-shadow: 0 0 0 3px rgba(158, 42, 43, 0.1);
}

/* Subject Selector Tab Grid (fy.html) */
.back-nav {
  margin-bottom: 1.75rem;
}

.back-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  color: var(--accent-burgundy);
  text-decoration: none;
  padding: 0.45rem 0.9rem;
  border-radius: var(--radius-sm);
  background: var(--accent-light);
  transition: background 0.2s ease;
}

.back-btn:hover {
  background: #f6e6e6;
}

.tab-selector-wrapper {
  margin: 1.5rem 0 2rem 0;
}

.tab-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 0.5rem;
  background: var(--bg-card);
  padding: 0.5rem;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
}

.tab-btn {
  font-family: var(--font-ui);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.8rem 0.5rem;
  background: transparent;
  border: none;
  border-radius: var(--radius-sm);
  color: var(--text-muted);
  cursor: pointer;
  transition: all 0.2s ease;
  text-align: center;
}

.tab-btn:hover {
  color: var(--accent-burgundy);
  background: rgba(158, 42, 43, 0.06);
}

.tab-btn.active {
  background: var(--accent-burgundy);
  color: #ffffff;
  box-shadow: var(--shadow-sm);
}

/* Tab Content Box */
.tab-content-container {
  background: #ffffff;
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: 2.25rem;
  box-shadow: var(--shadow-sm);
  margin-bottom: 3.5rem;
}

.tab-pane {
  display: none;
}

.tab-pane.active {
  display: block;
  animation: fadeIn 0.25s ease-in-out;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

.subject-header {
  margin-bottom: 2rem;
  padding-bottom: 1.25rem;
  border-bottom: 1px solid var(--border-color);
}

.subject-code {
  font-family: var(--font-ui);
  font-size: 0.8rem;
  font-weight: 700;
  color: var(--accent-burgundy);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.subject-title {
  font-family: var(--font-editorial);
  font-size: 1.85rem;
  font-weight: 700;
  color: var(--text-main);
  margin-top: 0.25rem;
}

.resource-group {
  margin-bottom: 2.25rem;
}

.resource-group-title {
  font-family: var(--font-ui);
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 1.15rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
}

.resource-group-title::before {
  content: '';
  display: inline-block;
  width: 8px;
  height: 8px;
  background-color: var(--accent-burgundy);
  border-radius: 50%;
}

.download-cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(290px, 1fr));
  gap: 1.15rem;
}

.download-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-sm);
  padding: 1.25rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  transition: all 0.2s ease;
}

.download-card:hover {
  border-color: var(--accent-burgundy);
  box-shadow: var(--shadow-sm);
  background: #ffffff;
}

.download-info {
  display: flex;
  flex-direction: column;
}

.download-title {
  font-family: var(--font-ui);
  font-size: 0.925rem;
  font-weight: 600;
  color: var(--text-main);
  margin-bottom: 0.3rem;
}

.download-meta {
  font-family: var(--font-ui);
  font-size: 0.775rem;
  color: var(--text-light);
}

.dl-btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  font-family: var(--font-ui);
  font-size: 0.8rem;
  font-weight: 700;
  padding: 0.55rem 0.95rem;
  background: var(--accent-burgundy);
  color: #ffffff;
  text-decoration: none;
  border-radius: var(--radius-sm);
  transition: background 0.2s ease;
  white-space: nowrap;
  flex-shrink: 0;
}

.dl-btn:hover {
  background: var(--accent-burgundy-hover);
}

/* Master Textbook Area (Below Tabs) */
.master-textbook-area {
  margin-top: 4.5rem;
  padding-top: 3rem;
  border-top: 2px solid var(--border-color);
}

.master-textbook-header {
  margin-bottom: 3rem;
  text-align: left;
}

.master-textbook-header h2 {
  font-family: var(--font-editorial);
  font-size: 2.15rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 0.5rem;
}

.master-textbook-header p {
  font-family: var(--font-editorial);
  font-size: 1.15rem;
  color: var(--text-muted);
  font-style: italic;
}

.subject-textbook-article {
  margin-bottom: 4rem;
  padding-bottom: 3rem;
  border-bottom: 1px dashed var(--border-dark);
}

.subject-textbook-article:last-child {
  border-bottom: none;
}

/* Footer */
.site-footer {
  border-top: 1px solid var(--border-color);
  background: var(--bg-card);
  padding: 3.5rem 1.5rem 2rem 1.5rem;
  margin-top: 6rem;
  font-family: var(--font-ui);
  font-size: 0.875rem;
  color: var(--text-muted);
}

.footer-inner {
  max-width: var(--content-max-width);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: 2.5rem;
  margin-bottom: 2.5rem;
}

.footer-col h4 {
  font-size: 0.95rem;
  font-weight: 700;
  color: var(--text-main);
  margin-bottom: 1.15rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.footer-col p {
  line-height: 1.65;
  margin-bottom: 0.85rem;
  font-size: 0.875rem;
}

.footer-links {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 0.65rem;
}

.footer-links a {
  color: var(--text-muted);
  text-decoration: none;
  transition: color 0.2s ease;
}

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

.footer-bottom {
  max-width: var(--content-max-width);
  margin: 0 auto;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.8rem;
  color: var(--text-light);
}

/* Responsive Breakpoints */
@media (max-width: 960px) {
  .layout-grid {
    grid-template-columns: 1fr;
    gap: 2.5rem;
  }

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

  .tab-grid {
    grid-template-columns: repeat(3, 1fr);
  }

  .footer-inner {
    grid-template-columns: 1fr 1fr;
  }
}

@media (max-width: 768px) {
  .site-header {
    flex-direction: column;
    gap: 1rem;
    align-items: center;
    text-align: center;
    padding: 1rem;
  }

  .nav-menu {
    justify-content: center;
    flex-wrap: wrap;
    gap: 1rem;
    width: 100%;
  }

  .article-title {
    font-size: 1.95rem;
  }

  .article-body p {
    text-align: left;
  }

  .tab-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 0.4rem;
  }

  .tab-btn {
    font-size: 0.8rem;
    padding: 0.7rem 0.35rem;
  }

  .download-cards-grid {
    grid-template-columns: 1fr;
  }

  .download-card {
    flex-direction: column;
    align-items: stretch;
    text-align: left;
  }

  .dl-btn {
    justify-content: center;
    width: 100%;
    padding: 0.7rem;
  }

  .footer-inner {
    grid-template-columns: 1fr;
    gap: 1.75rem;
  }

  .footer-bottom {
    flex-direction: column;
    gap: 0.75rem;
    text-align: center;
  }
}