:root {
  --sidebar-width: 250px;
  --header-height: 60px;
  --brand: #004080;
  --brand-light: #0059b3;
  --bg-light: #f4f6f8;
  --bg-content: #ffffff;
  --bg-heading: #e6f0ff;
  --text-dark: #333;
  --text-light: #fff;
  --border-color: #e3e6ea;
}
header {
  text-align: center;
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  font-family: "Segoe UI", Arial, sans-serif;
  background: #fafbfc;
  color: var(--text-dark);
  line-height: 1.6;
}

/* Overlay for mobile */
.overlay {
  position: fixed;
  inset: 0;
  background: rgba(0, 0, 0, 0.4);
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.3s ease;
  z-index: 900;
}
body.sidebar-open .overlay {
  opacity: 1;
  pointer-events: auto;
}

/* Sidebar styling */
.sidebar {
  position: fixed;
  top: 0;
  left: -var(--sidebar-width);
  width: var(--sidebar-width);
  height: 100%;
  background: var(--bg-light);
  border-right: 1px solid var(--border-color);
  padding: 16px;
  transition: transform 0.3s ease, left 0.3s ease;
  overflow-y: auto;
  z-index: 1000;
  transform: translateX(-100%);
  box-shadow: 2px 0 8px rgba(0, 0, 0, 0.05);
}
body.sidebar-open .sidebar {
  transform: translateX(0);
  left: 0;
}

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

.sidebar ul li strong {
  display: block;
  margin: 20px 0 8px;
  font-size: 0.85rem;
  color: var(--brand);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.sidebar a {
  display: block;
  padding: 10px 12px;
  color: var(--text-dark);
  text-decoration: none;
  border-radius: 6px;
  transition: background 0.2s ease, color 0.2s ease, padding-left 0.2s ease;
}
.sidebar a:hover {
  background: var(--brand);
  color: var(--text-light);
  padding-left: 16px;
}
.sidebar a.active {
  background: var(--brand);
  color: var(--text-light);
  font-weight: bold;
}

/* Menu button */
.menu-btn {
  background: var(--brand);
  color: var(--text-light);
  border: none;
  padding: 10px 14px;
  border-radius: 4px;
  font-size: 1rem;
  cursor: pointer;
  transition: background 0.2s ease, transform 0.1s ease;
}
.menu-btn:hover {
  background: var(--brand-light);
}
.menu-btn:active {
  transform: scale(0.97);
}

/* Content area */
.content {
  padding: 20px;
  transition: margin-left 0.3s ease;
  background: var(--bg-content);
  border-radius: 8px;
  margin: 20px;
  
  box-shadow: 0 2px 6px rgba(0,0,0,0.05);
}

/* Headings with background */
.content h1,
.content h2,
.content h3 {
  background: var(--bg-heading);
  padding: 10px 14px;
  border-radius: 6px;
  margin-top: 0;
  margin-bottom: 1em;
  box-shadow: 0 1px 3px rgba(0,0,0,0.05);
}

.content h1 {
  color: var(--brand);
  font-size: 1.8rem;
}
.content h2 {
  color: var(--brand);
  font-size: 1.4rem;
}
.content h3 {
  color: var(--brand);
  font-size: 1.2rem;
}

/* Normal content blocks */
.content p,
.content ul,
.content ol {
  background: #fafcff; /* very light tint */
  padding: 12px 14px;
  border-radius: 6px;
  margin-bottom: 1em;
  box-shadow: 0 1px 3px rgba(0,0,0,0.03);
}

/* Lists inside content */
.content ul li,
.content ol li {
  margin-bottom: 0.4em;
}

/* Tables */
.content table {
  width: 100%;
  border-collapse: collapse;
  margin: 1em 0;
  background: #ffffff;
  border-radius: 6px;
  overflow: hidden;
  box-shadow: 0 1px 4px rgba(0,0,0,0.05);
}

.content th,
.content td {
  border: 1px solid #ddd;
  padding: 8px 12px;
  text-align: left;
}

.content th {
  background: var(--bg-heading);
  color: var(--brand);
  font-weight: 600;
}

/* Code blocks */
.content pre,
.content code {
  font-family: Consolas, monospace;
  background: #f4f6f8;
  padding: 6px 8px;
  border-radius: 4px;
}

.content pre {
  display: block;
  padding: 12px;
  overflow-x: auto;
  box-shadow: inset 0 0 4px rgba(0,0,0,0.05);
}

/* Desktop: push content when sidebar open */
@media (min-width: 769px) {
  body.sidebar-open .content {
    margin-left: var(--sidebar-width);
  }
}