@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600;700&family=JetBrains+Mono:wght@400;500&display=swap');

/* ==========================================================================
   Design System & Custom Properties (Tokens)
   ========================================================================== */
:root {
  /* Dark Theme Variables (Default) */
  --bg-primary: #0b0f19;
  --bg-secondary: #111827;
  --bg-tertiary: #1f2937;
  --text-primary: #f9fafb;
  --text-secondary: #9ca3af;
  --text-tertiary: #6b7280;
  --accent: #10b981;
  --accent-hover: #059669;
  --accent-rgb: 16, 185, 129;
  --border-color: rgba(255, 255, 255, 0.08);
  --border-hover: rgba(16, 185, 129, 0.3);
  --card-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
  --header-blur: rgba(11, 15, 25, 0.8);
  --shadow-color: rgba(0, 0, 0, 0.3);

  /* Spacing */
  --spacing-xs: 0.5rem;
  --spacing-sm: 1rem;
  --spacing-md: 1.5rem;
  --spacing-lg: 2rem;
  --spacing-xl: 3rem;
  --spacing-xxl: 5rem;

  /* Typography */
  --font-sans: 'Inter', system-ui, -apple-system, sans-serif;
  --font-mono: 'JetBrains Mono', monospace;

  /* Transitions */
  --transition-fast: 0.2s cubic-bezier(0.16, 1, 0.3, 1);
  --transition-normal: 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

/* Light Theme Variables */
:root.light-theme {
  --bg-primary: #f8fafc;
  --bg-secondary: #ffffff;
  --bg-tertiary: #f1f5f9;
  --text-primary: #0f172a;
  --text-secondary: #475569;
  --text-tertiary: #94a3b8;
  --accent: #059669;
  --accent-hover: #047857;
  --accent-rgb: 5, 150, 105;
  --border-color: rgba(15, 23, 42, 0.08);
  --border-hover: rgba(5, 150, 105, 0.3);
  --card-shadow: 0 10px 30px -10px rgba(15, 23, 42, 0.05);
  --header-blur: rgba(248, 250, 252, 0.8);
  --shadow-color: rgba(15, 23, 42, 0.05);
}

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

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

body {
  font-family: var(--font-sans);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

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

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

button {
  cursor: pointer;
  border: none;
  background: none;
  font-family: inherit;
}

/* ==========================================================================
   Typography & Headers
   ========================================================================== */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.2;
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

h1 {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-sm);
}

@media (min-width: 768px) {
  h1 { font-size: 3.5rem; }
}

h2 {
  font-size: 1.8rem;
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
  position: relative;
  display: inline-block;
}

h2::after {
  content: '';
  position: absolute;
  left: 0;
  bottom: -4px;
  width: 2rem;
  height: 3px;
  background-color: var(--accent);
  border-radius: 2px;
}

h3 {
  font-size: 1.35rem;
  margin-bottom: var(--spacing-xs);
}

p {
  color: var(--text-secondary);
  font-size: 1rem;
  margin-bottom: var(--spacing-md);
  max-width: 75ch;
}

strong {
  color: var(--text-primary);
}

/* ==========================================================================
   Layout & Utility Classes
   ========================================================================== */
.container {
  width: 100%;
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-md);
}

.section {
  padding: var(--spacing-xxl) 0;
}

/* Flex utilities */
.flex { display: flex; }
.align-center { align-items: center; }
.justify-between { justify-content: space-between; }
.gap-sm { gap: var(--spacing-sm); }
.gap-md { gap: var(--spacing-md); }
.gap-lg { gap: var(--spacing-lg); }

/* Badges */
.badge {
  display: inline-block;
  padding: 0.25rem 0.75rem;
  border-radius: 9999px;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  background-color: rgba(var(--accent-rgb), 0.1);
  color: var(--accent);
  border: 1px solid rgba(var(--accent-rgb), 0.15);
  margin-bottom: var(--spacing-sm);
}

.badge-mono {
  font-family: var(--font-mono);
  background-color: var(--bg-tertiary);
  color: var(--text-secondary);
  border: 1px solid var(--border-color);
}

/* Buttons & Interactive */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--spacing-xs);
  padding: 0.75rem 1.5rem;
  border-radius: 8px;
  font-weight: 500;
  font-size: 0.95rem;
  transition: all var(--transition-fast);
  white-space: nowrap;
}

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

.btn-primary:hover {
  background-color: var(--accent-hover);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(var(--accent-rgb), 0.2);
}

.btn-primary:active {
  transform: translateY(-1px);
}

.btn-secondary {
  background-color: var(--bg-secondary);
  color: var(--text-primary);
  border: 1px solid var(--border-color);
}

.btn-secondary:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}

.btn-secondary:active {
  transform: translateY(-1px);
}

/* ==========================================================================
   Header & Navigation
   ========================================================================== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--header-blur);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--border-color);
  transition: all var(--transition-normal);
  height: 70px;
}

.nav {
  height: 100%;
}

.logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--text-primary);
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.logo span {
  color: var(--accent);
}

.nav-menu {
  display: flex;
  list-style: none;
  gap: var(--spacing-lg);
}

.nav-link {
  font-size: 0.95rem;
  font-weight: 500;
  color: var(--text-secondary);
  position: relative;
  padding: 0.25rem 0;
}

.nav-link:hover, .nav-link.active {
  color: var(--text-primary);
}

.nav-link::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background-color: var(--accent);
  transition: width var(--transition-fast);
}

.nav-link:hover::after, .nav-link.active::after {
  width: 100%;
}

/* Theme Toggle Button */
.theme-toggle {
  width: 40px;
  height: 40px;
  border-radius: 50%;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  color: var(--text-primary);
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: scale(1.05);
}

.theme-toggle svg {
  width: 20px;
  height: 20px;
  fill: currentColor;
}

.theme-toggle .sun { display: none; }
.theme-toggle .moon { display: block; }
:root.light-theme .theme-toggle .sun { display: block; }
:root.light-theme .theme-toggle .moon { display: none; }

/* Hamburger Menu Button */
.hamburger {
  display: none;
  flex-direction: column;
  gap: 6px;
  width: 30px;
  height: 24px;
}

.hamburger span {
  display: block;
  width: 100%;
  height: 2px;
  background-color: var(--text-primary);
  transition: all var(--transition-fast);
}

@media (max-width: 768px) {
  .hamburger {
    display: flex;
    z-index: 101;
  }

  .nav-menu {
    position: fixed;
    top: 70px;
    left: 0;
    width: 100%;
    height: calc(100vh - 70px);
    background-color: var(--bg-primary);
    flex-direction: column;
    align-items: center;
    padding-top: var(--spacing-xl);
    gap: var(--spacing-xl);
    transform: translateX(100%);
    transition: transform var(--transition-normal);
  }

  .nav-menu.active {
    transform: translateX(0);
  }

  /* Hamburger Animation */
  .hamburger.active span:nth-child(1) {
    transform: translateY(8px) rotate(45deg);
  }
  .hamburger.active span:nth-child(2) {
    opacity: 0;
  }
  .hamburger.active span:nth-child(3) {
    transform: translateY(-8px) rotate(-45deg);
  }
}

/* ==========================================================================
   Home Hero Section (index.html)
   ========================================================================== */
.hero-split {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-xl);
  align-items: center;
}

@media (min-width: 768px) {
  .hero-split {
    grid-template-columns: 1.2fr 0.8fr;
  }
}

.hero-content {
  display: flex;
  flex-direction: column;
  align-items: flex-start;
}

.hero-subtitle {
  font-family: var(--font-mono);
  color: var(--accent);
  font-size: 1rem;
  margin-bottom: var(--spacing-xs);
}

.hero-desc {
  font-size: 1.125rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-lg);
}

.hero-visual {
  display: flex;
  justify-content: center;
  align-items: center;
  position: relative;
}

.avatar-wrapper {
  position: relative;
  width: 280px;
  height: 280px;
  border-radius: 24px;
  overflow: hidden;
  border: 1px solid var(--border-color);
  box-shadow: var(--card-shadow);
  transition: transform var(--transition-normal);
}

.avatar-wrapper:hover {
  transform: translateY(-8px) rotate(2deg);
  border-color: var(--accent);
}

.avatar-wrapper img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

/* Decorative geometric frames */
.avatar-bg {
  position: absolute;
  width: 280px;
  height: 280px;
  border-radius: 24px;
  border: 2px solid rgba(var(--accent-rgb), 0.2);
  top: 15px;
  left: 15px;
  z-index: -1;
  transition: transform var(--transition-normal);
}

.avatar-wrapper:hover ~ .avatar-bg {
  transform: translate(-5px, -5px) rotate(-2deg);
  border-color: var(--accent);
}

/* ==========================================================================
   Bento Grid Layout (projects.html)
   ========================================================================== */
.bento-grid {
  display: grid;
  grid-template-columns: repeat(12, 1fr);
  gap: var(--spacing-md);
  margin-top: var(--spacing-lg);
}

.bento-card {
  grid-column: span 12;
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: var(--spacing-lg);
  box-shadow: var(--card-shadow);
  transition: all var(--transition-normal);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  text-decoration: none;
}

.bento-card:hover {
  transform: translateY(-5px);
  border-color: var(--border-hover);
  box-shadow: 0 20px 40px -15px var(--shadow-color);
}

.bento-card-header {
  margin-bottom: var(--spacing-md);
}

.bento-card-title {
  font-size: 1.25rem;
  margin-top: var(--spacing-xs);
  margin-bottom: var(--spacing-xs);
}

.bento-card-desc {
  font-size: 0.95rem;
  color: var(--text-secondary);
  margin-bottom: var(--spacing-md);
  line-height: 1.5;
}

.bento-card-footer {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.875rem;
  font-weight: 500;
  margin-top: auto;
}

.bento-card-link {
  color: var(--accent);
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.bento-card-link svg {
  width: 16px;
  height: 16px;
  transition: transform var(--transition-fast);
}

.bento-card:hover .bento-card-link svg {
  transform: translateX(4px);
}

/* Bento Card Grid Positioning definitions for Larger Screens */
@media (min-width: 768px) {
  /* Rows definitions */
  .col-span-4 { grid-column: span 4; }
  .col-span-6 { grid-column: span 6; }
  .col-span-8 { grid-column: span 8; }
  .col-span-12 { grid-column: span 12; }
  
  /* Asymmetric Bento configurations */
  .p-1 { grid-column: span 4; }
  .p-2 { grid-column: span 8; }
  .p-3 { grid-column: span 8; }
  .p-4 { grid-column: span 4; }
  .p-5 { grid-column: span 12; } /* highlight */
  .p-6 { grid-column: span 6; }
  .p-7 { grid-column: span 6; }
}

/* ==========================================================================
   Project Detail Pages Content Styling
   ========================================================================== */
.project-layout {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-xl);
  margin-top: var(--spacing-xl);
}

@media (min-width: 1024px) {
  .project-layout {
    grid-template-columns: 3fr 1fr;
  }
}

.project-body {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 20px;
  padding: var(--spacing-lg);
  box-shadow: var(--card-shadow);
}

@media (min-width: 768px) {
  .project-body {
    padding: var(--spacing-xl);
  }
}

.project-meta-sidebar {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.meta-block {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: var(--spacing-md);
}

.meta-title {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  text-transform: uppercase;
  color: var(--text-tertiary);
  letter-spacing: 0.05em;
  margin-bottom: var(--spacing-xs);
  display: block;
}

.meta-value {
  font-weight: 600;
  color: var(--text-primary);
}

/* Outline styling for reports */
.outline-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xs);
}

.outline-link {
  font-size: 0.9rem;
  color: var(--text-secondary);
  display: block;
  padding: 4px 0;
  border-left: 2px solid transparent;
  padding-left: 10px;
}

.outline-link:hover {
  color: var(--accent);
  border-left-color: var(--accent);
}

/* Custom Markdown Alert/Callout Boxes */
.callout {
  padding: var(--spacing-md);
  border-radius: 12px;
  margin: var(--spacing-md) 0;
  border-left: 4px solid var(--border-color);
}

.callout p:last-child {
  margin-bottom: 0;
}

.callout-note {
  background-color: rgba(var(--accent-rgb), 0.05);
  border-left-color: var(--accent);
}

.callout-important {
  background-color: rgba(239, 68, 68, 0.05);
  border-left-color: #ef4444;
}

.callout-title {
  font-weight: 700;
  font-size: 0.95rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--spacing-xs);
  display: flex;
  align-items: center;
  gap: var(--spacing-xs);
}

.callout-note .callout-title { color: var(--accent); }
.callout-important .callout-title { color: #ef4444; }

/* Lists inside reports */
.project-body ul, .project-body ol {
  margin-left: var(--spacing-lg);
  margin-bottom: var(--spacing-md);
  color: var(--text-secondary);
}

.project-body li {
  margin-bottom: var(--spacing-xs);
}

/* ==========================================================================
   Tables & Data Presentation
   ========================================================================== */
.table-responsive {
  width: 100%;
  overflow-x: auto;
  margin: var(--spacing-lg) 0;
  border-radius: 12px;
  border: 1px solid var(--border-color);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
}

table {
  width: 100%;
  border-collapse: collapse;
  text-align: left;
  font-size: 0.925rem;
}

th, td {
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border-color);
}

th {
  background-color: var(--bg-tertiary);
  font-weight: 600;
  color: var(--text-primary);
  text-transform: uppercase;
  font-size: 0.75rem;
  letter-spacing: 0.05em;
}

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

tr:nth-child(even) td {
  background-color: rgba(255, 255, 255, 0.01);
}

:root.light-theme tr:nth-child(even) td {
  background-color: rgba(0, 0, 0, 0.01);
}

tr:hover td {
  background-color: rgba(var(--accent-rgb), 0.03);
}

/* Rating cells in Table (Bài 2) */
.rating-high {
  color: #10b981;
  font-weight: 600;
}
.rating-medium {
  color: #f59e0b;
  font-weight: 600;
}

/* ==========================================================================
   Code blocks & Technical syntax
   ========================================================================== */
code {
  font-family: var(--font-mono);
  font-size: 0.875rem;
  background-color: var(--bg-tertiary);
  color: var(--accent);
  padding: 2px 6px;
  border-radius: 4px;
}

pre {
  background-color: var(--bg-tertiary);
  border: 1px solid var(--border-color);
  border-radius: 12px;
  padding: var(--spacing-md);
  overflow-x: auto;
  margin: var(--spacing-md) 0;
}

pre code {
  color: var(--text-primary);
  background: none;
  padding: 0;
  border-radius: 0;
  font-size: 0.85rem;
}

/* Simple Syntax Highlighting for Java OOP (Bài 5) */
.keyword { color: #f43f5e; font-weight: 600; }
.class-name { color: var(--accent); font-weight: 600; }
.comment { color: var(--text-tertiary); font-style: italic; }
.string { color: #38bdf8; }

/* ==========================================================================
   Gallery & Image Styling
   ========================================================================== */
.media-container {
  margin: var(--spacing-lg) 0;
  border-radius: 16px;
  overflow: hidden;
  border: 1px solid var(--border-color);
  box-shadow: 0 4px 20px -2px rgba(0,0,0,0.2);
}

.media-container img {
  width: 100%;
  height: auto;
  object-fit: cover;
  transition: transform var(--transition-normal);
}

.media-container:hover img {
  transform: scale(1.02);
}

.media-caption {
  padding: var(--spacing-sm);
  background-color: var(--bg-tertiary);
  border-top: 1px solid var(--border-color);
  font-size: 0.875rem;
  color: var(--text-secondary);
  text-align: center;
  max-width: 100%;
}

.grid-2col {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-md);
}

@media (min-width: 768px) {
  .grid-2col {
    grid-template-columns: 1fr 1fr;
  }
}

/* ==========================================================================
   Summary/Reflection layout elements (summary.html)
   ========================================================================== */
.summary-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--spacing-lg);
  margin-top: var(--spacing-xl);
}

@media (min-width: 768px) {
  .summary-grid {
    grid-template-columns: 1fr 1fr;
  }
}

.summary-card {
  background-color: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: 16px;
  padding: var(--spacing-lg);
  box-shadow: var(--card-shadow);
}

.summary-icon {
  width: 48px;
  height: 48px;
  border-radius: 12px;
  background-color: rgba(var(--accent-rgb), 0.1);
  color: var(--accent);
  display: flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--spacing-md);
}

.summary-icon svg {
  width: 24px;
  height: 24px;
}

/* ==========================================================================
   Footer Section
   ========================================================================== */
.footer {
  border-top: 1px solid var(--border-color);
  padding: var(--spacing-xl) 0;
  text-align: center;
  font-size: 0.875rem;
  color: var(--text-tertiary);
}

.footer p {
  margin-left: auto;
  margin-right: auto;
}

.footer-logo {
  font-weight: 700;
  color: var(--text-primary);
  margin-bottom: var(--spacing-xs);
  display: inline-flex;
  align-items: center;
  gap: 4px;
}

.footer-logo span {
  color: var(--accent);
}

.footer-links {
  display: flex;
  justify-content: center;
  gap: var(--spacing-md);
  margin-top: var(--spacing-sm);
  margin-bottom: var(--spacing-md);
}

.footer-link:hover {
  color: var(--accent);
}