/* ============================================
   PROFESSIONAL ACADEMIC STYLESHEET
   Minimal, clean, and modular design
   ============================================ */

:root {
  --primary-dark: #2c3e50;
  --primary-light: #34495e;
  --accent-blue: #3498db;
  --accent-blue-dark: #2980b9;
  --background: #ecf0f1;
  --white: #ffffff;
  --text-dark: #2c3e50;
  --text-light: #555555;
  --border: #bdc3c7;
  --code-bg: #f7f7f7;
  --code-border: #e0e0e0;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

/* ============================================
   BASE TYPOGRAPHY
   ============================================ */

html {
  scroll-behavior: smooth;
  font-size: 16px;
}

body {
  font-family: 'Segoe UI', 'Helvetica Neue', -apple-system, BlinkMacSystemFont, sans-serif;
  line-height: 1.6;
  color: var(--text-dark);
  background-color: var(--white);
}

h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  line-height: 1.3;
  margin-top: 1.5em;
  margin-bottom: 0.5em;
  color: var(--primary-dark);
}

h1 {
  font-size: 2.5rem;
  border-bottom: 3px solid var(--accent-blue);
  padding-bottom: 0.5rem;
}

h2 {
  font-size: 1.8rem;
  margin-top: 1.8em;
  margin-bottom: 0.7em;
}

h3 {
  font-size: 1.4rem;
  margin-top: 1.5em;
}

h4 {
  font-size: 1.1rem;
  margin-top: 1.3em;
}

p {
  margin-bottom: 1em;
  text-align: justify;
  color: var(--text-light);
}

a {
  color: var(--accent-blue);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: color 0.2s, border-bottom 0.2s;
}

a:hover {
  color: var(--accent-blue-dark);
  border-bottom: 1px solid var(--accent-blue-dark);
}

/* ============================================
   HEADER & NAVIGATION
   ============================================ */

header {
  background-color: var(--primary-dark);
  color: var(--white);
  padding: 1.5rem 0;
  box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header-content {
  max-width: 900px;
  margin: 0 auto;
  padding: 0 2rem;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--white);
  text-decoration: none;
}

.site-title:hover {
  color: var(--accent-blue);
  border-bottom: none;
}

nav ul {
  list-style: none;
  display: flex;
  gap: 2rem;
}

nav a {
  color: var(--white);
  border-bottom: 2px solid transparent;
  transition: color 0.2s, border-bottom 0.2s;
}

nav a:hover {
  color: var(--accent-blue);
  border-bottom: 2px solid var(--accent-blue);
}

/* ============================================
   MAIN CONTENT
   ============================================ */

main {
  max-width: 900px;
  margin: 0 auto;
  padding: 3rem 2rem;
  min-height: calc(100vh - 200px);
}

.page-intro {
  font-size: 1.1rem;
  color: var(--text-light);
  margin-bottom: 2rem;
  line-height: 1.8;
}

.section {
  margin-bottom: 3rem;
}

.section > h2:first-child {
  margin-top: 0;
}

/* ============================================
   CARDS (for index page navigation)
   ============================================ */

.cards-container {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: 2rem;
  margin-top: 2rem;
}

.card {
  background-color: var(--white);
  border: 2px solid var(--border);
  border-radius: 4px;
  padding: 2rem;
  transition: box-shadow 0.3s, border-color 0.3s;
  text-decoration: none;
  color: var(--text-dark);
}

.card:hover {
  border-color: var(--accent-blue);
  box-shadow: 0 4px 12px rgba(52, 152, 219, 0.15);
}

.card-title {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--primary-dark);
  margin-bottom: 0.5rem;
}

.card-subtitle {
  color: var(--accent-blue);
  font-weight: 600;
  font-size: 0.9rem;
  margin-bottom: 1rem;
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.card-description {
  color: var(--text-light);
  line-height: 1.6;
  margin-bottom: 1rem;
}

.card-link {
  color: var(--accent-blue);
  font-weight: 600;
  display: inline-block;
  margin-top: 0.5rem;
}

/* ============================================
   CODE BLOCKS
   ============================================ */

pre {
  background-color: var(--code-bg);
  border: 1px solid var(--code-border);
  border-radius: 4px;
  padding: 1.5rem;
  overflow-x: auto;
  margin: 1.5rem 0;
  font-size: 0.95rem;
  line-height: 1.5;
}

code {
  font-family: 'Courier New', 'Consolas', monospace;
  color: var(--primary-dark);
}

pre code {
  color: var(--primary-dark);
  background: none;
  padding: 0;
}

/* Inline code */
p code, li code, h2 code, h3 code, h4 code {
  background-color: var(--code-bg);
  padding: 0.2rem 0.4rem;
  border-radius: 3px;
  font-size: 0.9em;
}

/* ============================================
   LISTS
   ============================================ */

ul, ol {
  margin-left: 1.5rem;
  margin-bottom: 1rem;
}

li {
  margin-bottom: 0.5rem;
  color: var(--text-light);
}

/* ============================================
   FOOTER
   ============================================ */

footer {
  background-color: var(--primary-dark);
  color: var(--white);
  text-align: center;
  padding: 2rem;
  margin-top: 3rem;
  font-size: 0.95rem;
}

.footer-content {
  max-width: 900px;
  margin: 0 auto;
}

.footer-links {
  margin-bottom: 1rem;
}

.footer-links a {
  color: var(--accent-blue);
  margin: 0 1rem;
}

.footer-links a:hover {
  color: var(--white);
  border-bottom: 1px solid var(--white);
}

.footer-meta {
  font-size: 0.9rem;
  color: var(--white);
}

.footer-meta p {
  color: var(--white);
  margin: 0;
}

/* ============================================
   BLOCKQUOTES
   ============================================ */

blockquote {
  border-left: 4px solid var(--accent-blue);
  padding-left: 1.5rem;
  margin: 1.5rem 0;
  color: var(--text-light);
  font-style: italic;
}

/* ============================================
   TABLES
   ============================================ */

table {
  width: 100%;
  border-collapse: collapse;
  margin: 1.5rem 0;
  border: 1px solid var(--border);
}

th, td {
  padding: 0.75rem 1rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
}

th {
  background-color: var(--code-bg);
  font-weight: 700;
  color: var(--primary-dark);
}

tr:hover {
  background-color: var(--background);
}

/* ============================================
   BUTTONS & LINKS
   ============================================ */

.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  background-color: var(--accent-blue);
  color: var(--white);
  text-decoration: none;
  border-radius: 4px;
  transition: background-color 0.2s;
  font-weight: 600;
  border: none;
  cursor: pointer;
}

.btn:hover {
  background-color: var(--accent-blue-dark);
}

.btn-secondary {
  background-color: var(--border);
  color: var(--primary-dark);
}

.btn-secondary:hover {
  background-color: #95a5a6;
}

/* ============================================
   RESPONSIVE DESIGN
   ============================================ */

@media (max-width: 768px) {
  .header-content {
    flex-direction: column;
    gap: 1rem;
  }

  nav ul {
    flex-direction: column;
    gap: 0.5rem;
  }

  h1 {
    font-size: 1.8rem;
  }

  h2 {
    font-size: 1.4rem;
  }

  main {
    padding: 2rem 1rem;
  }

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

  pre {
    font-size: 0.85rem;
    padding: 1rem;
  }
}

/* ============================================
   UTILITY CLASSES
   ============================================ */

.text-center {
  text-align: center;
}

.text-muted {
  color: var(--text-light);
}

.mt-2 {
  margin-top: 2rem;
}

.mb-2 {
  margin-bottom: 2rem;
}

.highlight {
  background-color: #fffacd;
  padding: 0.2rem 0.4rem;
  border-radius: 3px;
}