/* ==========================================================================
   TutorialsPoint-Inspired Minimal JavaScript Tutorial Stylesheet (style.css)
   Clean, simple, mobile-first responsive design.
   Primary Accent Color: Blue (#0d6efd / #3b82f6)
   System-detected theme (automatic light/dark based on OS setting).
   ========================================================================== */

/* 1. Light Mode Colors (Default) */
:root {
  --tp-blue: #0d6efd;
  --tp-blue-hover: #0b5ed7;
  --tp-blue-light: #e7f1ff;

  --bg-body: #ffffff;
  --bg-sidebar: #f8f9fa;
  --bg-card: #ffffff;
  --bg-code: #f6f8fa;
  --bg-terminal: #1e1e1e;
  --border-color: #e5e7eb;
  --border-dark: #cbd5e1;

  --text-main: #212529;
  --text-muted: #6c757d;
  --text-heading: #111827;

  --header-height: 52px;
  --sidebar-width: 270px;
  --content-max-width: 880px;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --font-mono: Consolas, "SFMono-Regular", Menlo, Monaco, "Courier New", monospace;
}

/* 2. System-Detected Dark Mode (Automatic based on OS setting) */
@media (prefers-color-scheme: dark) {
  :root {
    --tp-blue: #3b82f6;
    --tp-blue-hover: #2563eb;
    --tp-blue-light: #172554;

    --bg-body: #121820;
    --bg-sidebar: #182230;
    --bg-card: #1c2838;
    --bg-code: #16202c;
    --bg-terminal: #0b1016;
    --border-color: #2a3b50;
    --border-dark: #374d68;

    --text-main: #e2e8f0;
    --text-muted: #94a3b8;
    --text-heading: #f8fafc;
  }
}

/* 3. Base Reset & Typography */
* {
  box-sizing: border-box;
  margin: 0;
  padding: 0;
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-body);
  color: var(--text-main);
  line-height: 1.65;
  font-size: 15px;
  -webkit-font-smoothing: antialiased;
  overflow-x: hidden;
}

a {
  color: var(--tp-blue);
  text-decoration: none;
}

a:hover {
  text-decoration: underline;
}

/* 4. Top Header */
.tp-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--header-height);
  background: var(--bg-card);
  border-bottom: 1px solid var(--border-color);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 1rem;
  z-index: 1000;
  gap: 12px;
}

.header-left {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-shrink: 0;
}

.tp-brand {
  display: flex;
  align-items: center;
  gap: 7px;
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--text-heading);
  text-decoration: none;
  white-space: nowrap;
}

.tp-logo-badge {
  background: var(--tp-blue);
  color: #ffffff;
  font-weight: 800;
  padding: 2px 7px;
  border-radius: 4px;
  font-size: 0.85rem;
  font-family: var(--font-mono);
}

.tp-brand-text {
  display: inline-block;
}

/* Mobile Hamburger Button */
.mobile-toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 5px 10px;
  font-size: 1.15rem;
  color: var(--text-main);
  cursor: pointer;
  line-height: 1;
}

.mobile-toggle:hover {
  background: var(--bg-sidebar);
}

/* Search Bar (Clean & Adaptive) */
.header-search {
  position: relative;
  width: 320px;
  max-width: 100%;
}

.search-input {
  width: 100%;
  padding: 7px 32px 7px 12px;
  border: 1px solid var(--border-color);
  border-radius: 4px;
  font-size: 0.85rem;
  background: var(--bg-sidebar);
  color: var(--text-main);
  outline: none;
  transition: all 0.2s ease;
}

.search-input:focus {
  border-color: var(--tp-blue);
  background: var(--bg-card);
  box-shadow: 0 0 0 2px rgba(13, 110, 253, 0.18);
}

.search-icon-label {
  position: absolute;
  right: 10px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--text-muted);
  font-size: 0.85rem;
  pointer-events: none;
}

.search-results-dropdown {
  position: absolute;
  top: calc(100% + 4px);
  left: 0;
  right: 0;
  max-height: 380px;
  overflow-y: auto;
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  box-shadow: 0 8px 24px rgba(0, 0, 0, 0.15);
  display: none;
  z-index: 1050;
}

.search-item {
  padding: 10px 14px;
  border-bottom: 1px solid var(--border-color);
  cursor: pointer;
  font-size: 0.85rem;
  display: flex;
  flex-direction: column;
}

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

.search-item:hover, .search-item.selected {
  background: var(--tp-blue-light);
  color: var(--tp-blue);
}

.search-item-part {
  font-size: 0.72rem;
  color: var(--text-muted);
  text-transform: uppercase;
  margin-bottom: 2px;
}

.search-item-title {
  font-weight: 600;
  color: var(--text-heading);
}

.search-empty {
  padding: 14px;
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* 5. Main Layout Structure */
.tp-layout {
  display: flex;
  margin-top: var(--header-height);
  min-height: calc(100vh - var(--header-height));
}

/* 6. Left Sidebar: Table of Contents (TOC) */
.tp-sidebar {
  width: var(--sidebar-width);
  background: var(--bg-sidebar);
  border-right: 1px solid var(--border-color);
  position: fixed;
  top: var(--header-height);
  bottom: 0;
  left: 0;
  overflow-y: auto;
  overflow-x: hidden;
  padding: 0.75rem 0 2rem 0;
  z-index: 900;
  -webkit-overflow-scrolling: touch;
}

.tp-sidebar::-webkit-scrollbar {
  width: 5px;
}

.tp-sidebar::-webkit-scrollbar-thumb {
  background: var(--border-color);
  border-radius: 3px;
}

/* Sidebar Top Mobile Header (Title + Close Button) */
.sidebar-mobile-header {
  display: none;
  align-items: center;
  justify-content: space-between;
  padding: 10px 1.25rem;
  border-bottom: 1px solid var(--border-color);
  margin-bottom: 8px;
}

.sidebar-mobile-title {
  font-weight: 700;
  font-size: 0.95rem;
  color: var(--text-heading);
}

.sidebar-close-btn {
  background: none;
  border: none;
  font-size: 1.25rem;
  color: var(--text-muted);
  cursor: pointer;
  padding: 4px 8px;
  line-height: 1;
}

.toc-header-title {
  font-size: 0.78rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  color: var(--text-muted);
  padding: 4px 1.25rem 8px 1.25rem;
}

.toc-section {
  margin-bottom: 10px;
}

.toc-category-title {
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--text-heading);
  padding: 6px 1.25rem;
  background: rgba(0, 0, 0, 0.02);
  border-top: 1px solid var(--border-color);
  border-bottom: 1px solid var(--border-color);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.toc-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.toc-link {
  display: block;
  padding: 7px 1.25rem;
  font-size: 0.85rem;
  color: var(--text-main);
  text-decoration: none;
  border-left: 3px solid transparent;
  transition: all 0.15s ease;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}

.toc-link:hover {
  background: rgba(0, 0, 0, 0.04);
  color: var(--tp-blue);
  text-decoration: none;
}

.toc-link.active {
  background: var(--tp-blue-light);
  color: var(--tp-blue);
  font-weight: 700;
  border-left-color: var(--tp-blue);
}

/* 7. Main Content Area */
.tp-main-content {
  flex: 1;
  margin-left: var(--sidebar-width);
  padding: 2rem 3rem 4rem 3rem;
  background: var(--bg-body);
  display: flex;
  justify-content: center;
  min-width: 0;
}

.content-wrapper {
  width: 100%;
  max-width: var(--content-max-width);
  min-width: 0;
}

/* Navigation Buttons Bar (< Previous | Next >) */
.nav-buttons-bar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 10px 0;
  margin-bottom: 1.5rem;
  border-bottom: 1px solid var(--border-color);
  gap: 10px;
}

.nav-buttons-bar.bottom {
  margin-top: 2.5rem;
  margin-bottom: 0;
  border-top: 1px solid var(--border-color);
  border-bottom: none;
  padding-top: 1.5rem;
}

.btn-tp-nav {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 6px;
  background: var(--bg-card);
  border: 1px solid var(--tp-blue);
  color: var(--tp-blue);
  padding: 7px 18px;
  border-radius: 4px;
  font-size: 0.875rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: all 0.15s ease;
  min-height: 38px;
  white-space: nowrap;
}

.btn-tp-nav:hover {
  background: var(--tp-blue);
  color: #ffffff;
  text-decoration: none;
}

.btn-tp-nav.disabled {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
  border-color: var(--border-color);
  color: var(--text-muted);
}

/* Heading & Divider */
.page-title {
  font-size: 1.85rem;
  font-weight: 700;
  color: var(--text-heading);
  margin-bottom: 0.5rem;
  line-height: 1.3;
  word-wrap: break-word;
}

.title-divider {
  border: none;
  border-top: 3px solid var(--tp-blue);
  margin-bottom: 1.5rem;
  width: 60px;
}

/* Content Body */
.content-body p {
  margin-bottom: 1.25rem;
  color: var(--text-main);
  line-height: 1.7;
}

.content-body h3 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--text-heading);
  margin: 1.75rem 0 0.75rem 0;
  border-bottom: 1px solid var(--border-color);
  padding-bottom: 6px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.content-body h3 i {
  color: var(--tp-blue);
  font-size: 1.05rem;
}

.btn-tp-nav i {
  font-size: 0.85rem;
}

.btn-code i {
  margin-right: 3px;
  font-size: 0.8rem;
}

.content-body ul, .content-body ol {
  margin: 0 0 1.25rem 1.5rem;
}

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

/* Formal Definition Callout */
.definition-box {
  background: var(--bg-sidebar);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--tp-blue);
  padding: 12px 18px;
  border-radius: 4px;
  margin: 1rem 0 1.5rem 0;
  font-size: 0.95rem;
  line-height: 1.65;
}

.definition-box strong {
  color: var(--tp-blue);
  font-weight: 700;
}

/* Logical Reasoning & Step-by-Step Logic */
.reasoning-list {
  list-style: none;
  padding: 0;
  margin: 1rem 0 1.5rem 0;
}

.reasoning-item {
  display: flex;
  gap: 12px;
  margin-bottom: 10px;
  background: var(--bg-sidebar);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  padding: 12px 16px;
}

.reasoning-badge {
  background: var(--tp-blue);
  color: #ffffff;
  font-weight: 700;
  font-size: 0.78rem;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  flex-shrink: 0;
  margin-top: 2px;
}

.reasoning-content {
  flex: 1;
  font-size: 0.9rem;
  line-height: 1.6;
}

.reasoning-title {
  font-weight: 700;
  color: var(--text-heading);
  margin-bottom: 2px;
}

/* Explanation Notes */
.explain-note {
  background: var(--tp-blue-light);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--tp-blue);
  padding: 10px 16px;
  border-radius: 4px;
  margin: 1rem 0;
  font-size: 0.88rem;
  line-height: 1.6;
}

/* Syntax Box */
.syntax-box {
  background: var(--bg-code);
  border: 1px solid var(--border-color);
  border-left: 4px solid var(--tp-blue);
  padding: 12px 16px;
  margin: 1rem 0 1.5rem 0;
  border-radius: 4px;
  font-family: var(--font-mono);
  font-size: 0.9rem;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-word;
}

/* Code Example Box */
.code-box-card {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 4px;
  margin: 1.25rem 0 1.75rem 0;
  overflow: hidden;
  width: 100%;
}

.code-box-header {
  background: var(--bg-sidebar);
  border-bottom: 1px solid var(--border-color);
  padding: 7px 12px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 8px;
}

.code-box-label {
  font-size: 0.75rem;
  font-weight: 700;
  text-transform: uppercase;
  color: var(--text-muted);
}

.code-box-actions {
  display: flex;
  gap: 8px;
}

.btn-code {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  padding: 4px 12px;
  border-radius: 3px;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--text-main);
  cursor: pointer;
  min-height: 28px;
}

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

.btn-code-run {
  background: var(--tp-blue);
  border-color: var(--tp-blue);
  color: #ffffff;
}

.btn-code-run:hover {
  background: var(--tp-blue-hover);
}

.code-textarea {
  width: 100%;
  min-height: 120px;
  padding: 12px;
  font-family: var(--font-mono);
  font-size: 0.88rem;
  line-height: 1.5;
  border: none;
  background: var(--bg-code);
  color: var(--text-main);
  outline: none;
  resize: vertical;
  white-space: pre;
  tab-size: 2;
  overflow-x: auto;
  -webkit-overflow-scrolling: touch;
}

/* Output Display Box */
.output-box {
  background: var(--bg-terminal);
  color: #d4d4d4;
  border-top: 1px solid var(--border-color);
  font-family: var(--font-mono);
  font-size: 0.84rem;
  padding: 10px 14px;
  max-height: 220px;
  overflow-y: auto;
  overflow-x: auto;
  white-space: pre-wrap;
  word-break: break-all;
  -webkit-overflow-scrolling: touch;
}

.output-header-title {
  font-size: 0.7rem;
  font-weight: 700;
  text-transform: uppercase;
  color: #888;
  margin-bottom: 4px;
}

/* Minimal Project Demo Box (for Part 26) */
.project-demo-box {
  background: var(--bg-card);
  border: 1px solid var(--border-color);
  border-radius: 6px;
  padding: 1.5rem;
  margin: 1.5rem 0;
  box-shadow: 0 1px 3px rgba(0, 0, 0, 0.05);
  overflow-x: auto;
}

/* Footer */
.tp-footer {
  margin-top: 3rem;
  padding-top: 1.5rem;
  border-top: 1px solid var(--border-color);
  text-align: center;
  color: var(--text-muted);
  font-size: 0.85rem;
}

/* 8. Responsive & Mobile Styling */
.sidebar-overlay {
  display: none;
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.5);
  backdrop-filter: blur(2px);
  z-index: 1050;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.25s ease;
}

.sidebar-overlay.active {
  display: block;
  opacity: 1;
  pointer-events: auto;
}

/* Tablets (max-width: 1024px) */
@media (max-width: 1024px) {
  .tp-main-content {
    padding: 1.5rem 2rem 3rem 2rem;
  }
}

/* Mobile & Small Screens (max-width: 860px) */
@media (max-width: 860px) {
  .mobile-toggle {
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }

  .tp-sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    width: min(300px, 85vw);
    background: var(--bg-card);
    z-index: 1100;
    transform: translateX(-100%);
    transition: transform 0.25s ease-in-out;
    box-shadow: none;
    padding-top: 0;
  }

  .tp-sidebar.open {
    transform: translateX(0);
    box-shadow: 4px 0 24px rgba(0, 0, 0, 0.3);
  }

  .sidebar-mobile-header {
    display: flex;
  }

  .tp-main-content {
    margin-left: 0;
    padding: 1.25rem 1rem 3rem 1rem;
    width: 100%;
  }

  .header-search {
    width: auto;
    flex: 1;
    max-width: 300px;
  }

  .search-input {
    font-size: 16px; /* Prevents auto-zoom on iOS safari */
  }

  .code-textarea {
    font-size: 14px;
  }

  .page-title {
    font-size: 1.5rem;
  }
}

/* Very Small Mobile Screens (max-width: 480px) */
@media (max-width: 480px) {
  .tp-header {
    padding: 0 0.75rem;
    gap: 8px;
  }

  .tp-brand-text {
    display: none; /* Hide brand text to keep search bar visible on tiny screens */
  }

  .header-search {
    max-width: 100%;
  }

  .search-input {
    padding-left: 8px;
  }

  .btn-tp-nav {
    padding: 6px 12px;
    font-size: 0.8rem;
  }
}