/* ============================================
   MyBlog - Custom Design System
   ============================================ */

/* ----- CSS Custom Properties (Theme) ----- */
:root {
  /* Colors - Light Theme */
  --color-primary: #6366f1;
  --color-primary-dark: #4f46e5;
  --color-primary-light: #818cf8;
  --color-accent: #f59e0b;
  --color-bg: #ffffff;
  --color-bg-alt: #f8fafc;
  --color-bg-card: #ffffff;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-text-muted: #94a3b8;
  --color-border: #e2e8f0;
  --color-border-light: #f1f5f9;
  --color-header-bg: linear-gradient(135deg, #6366f1 0%, #8b5cf6 50%, #a78bfa 100%);
  --color-header-text: #ffffff;
  --color-footer-bg: #1e293b;
  --color-footer-text: #cbd5e1;
  --color-code-bg: #1e293b;
  --color-code-text: #e2e8f0;
  --color-blockquote-border: #6366f1;
  --color-blockquote-bg: #f8fafc;
  --color-shadow: rgba(0, 0, 0, 0.08);
  --color-shadow-hover: rgba(0, 0, 0, 0.12);
  --color-overlay: rgba(0, 0, 0, 0.5);

  /* Typography */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Noto Sans SC', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Consolas', monospace;
  --font-size-xs: 0.75rem;
  --font-size-sm: 0.875rem;
  --font-size-base: 1rem;
  --font-size-lg: 1.125rem;
  --font-size-xl: 1.25rem;
  --font-size-2xl: 1.5rem;
  --font-size-3xl: 1.875rem;
  --font-size-4xl: 2.25rem;

  /* Spacing */
  --space-1: 0.25rem;
  --space-2: 0.5rem;
  --space-3: 0.75rem;
  --space-4: 1rem;
  --space-6: 1.5rem;
  --space-8: 2rem;
  --space-12: 3rem;
  --space-16: 4rem;

  /* Layout */
  --max-width: 1100px;
  --content-width: 720px;
  --sidebar-width: 320px;
  --header-height: 64px;
  --border-radius: 12px;
  --border-radius-sm: 8px;
  --border-radius-lg: 16px;

  /* Transitions */
  --transition-fast: 150ms ease;
  --transition-base: 250ms ease;
  --transition-slow: 400ms ease;
}

/* ----- Dark Theme ----- */
[data-theme="dark"] {
  --color-primary: #818cf8;
  --color-primary-dark: #6366f1;
  --color-primary-light: #a5b4fc;
  --color-bg: #0f172a;
  --color-bg-alt: #1e293b;
  --color-bg-card: #1e293b;
  --color-text: #e2e8f0;
  --color-text-secondary: #94a3b8;
  --color-text-muted: #64748b;
  --color-border: #334155;
  --color-border-light: #1e293b;
  --color-header-bg: linear-gradient(135deg, #1e1b4b 0%, #312e81 50%, #3730a3 100%);
  --color-header-text: #e0e7ff;
  --color-footer-bg: #020617;
  --color-footer-text: #64748b;
  --color-code-bg: #0f172a;
  --color-code-text: #e2e8f0;
  --color-blockquote-border: #818cf8;
  --color-blockquote-bg: #1e293b;
  --color-shadow: rgba(0, 0, 0, 0.3);
  --color-shadow-hover: rgba(0, 0, 0, 0.4);
}

/* ----- Base ----- */
*, *::before, *::after {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
  scroll-padding-top: 80px;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  font-size: var(--font-size-base);
  line-height: 1.7;
  color: var(--color-text);
  background-color: var(--color-bg);
  transition: background-color var(--transition-base), color var(--transition-base);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

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

a:hover {
  color: var(--color-primary-dark);
}

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

::selection {
  background: var(--color-primary);
  color: white;
}

/* ----- Reading Progress Bar ----- */
#reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 0%;
  height: 3px;
  background: linear-gradient(90deg, var(--color-primary), var(--color-accent));
  z-index: 9999;
  transition: width 100ms linear;
}

/* ----- Header / Navigation ----- */
.blog-header {
  background: var(--color-header-bg);
  color: var(--color-header-text);
  padding: var(--space-4) 0;
  position: sticky;
  top: 0;
  z-index: 1000;
  box-shadow: 0 2px 20px var(--color-shadow);
  backdrop-filter: blur(10px);
}

.blog-header-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.blog-header-logo {
  font-size: var(--font-size-2xl);
  font-weight: 800;
  letter-spacing: -0.5px;
  background: linear-gradient(135deg, #ffffff 0%, #c7d2fe 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  margin: 0;
}

.blog-header-logo a {
  color: inherit;
  -webkit-text-fill-color: transparent;
}

.blog-header-subtitle {
  font-size: var(--font-size-sm);
  opacity: 0.8;
  margin: var(--space-1) 0 0 0;
}

.header-actions {
  display: flex;
  align-items: center;
  gap: var(--space-3);
}

/* ----- Theme Toggle Button ----- */
.theme-toggle {
  background: rgba(255, 255, 255, 0.15);
  border: 1px solid rgba(255, 255, 255, 0.25);
  color: white;
  width: 40px;
  height: 40px;
  border-radius: 50%;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: var(--font-size-lg);
  transition: all var(--transition-fast);
}

.theme-toggle:hover {
  background: rgba(255, 255, 255, 0.25);
  transform: scale(1.1);
}

/* ----- Main Content ----- */
.blog-main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: var(--space-8) var(--space-6);
  min-height: calc(100vh - var(--header-height) - 200px);
}

/* ----- Article Cards ----- */
.article-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  padding: var(--space-8);
  margin-bottom: var(--space-6);
  transition: all var(--transition-base);
  position: relative;
  overflow: hidden;
}

.article-card::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: linear-gradient(180deg, var(--color-primary), var(--color-primary-light));
  opacity: 0;
  transition: opacity var(--transition-base);
}

.article-card:hover {
  transform: translateY(-3px);
  box-shadow: 0 12px 40px var(--color-shadow-hover);
  border-color: var(--color-primary-light);
}

.article-card:hover::before {
  opacity: 1;
}

.article-card-title {
  font-size: var(--font-size-2xl);
  font-weight: 700;
  line-height: 1.3;
  margin: 0 0 var(--space-3) 0;
}

.article-card-title a {
  color: var(--color-text);
  text-decoration: none;
}

.article-card-title a:hover {
  color: var(--color-primary);
}

.article-card-meta {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-4);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  margin-bottom: var(--space-4);
}

.article-card-meta span {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.article-card-excerpt {
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin-bottom: var(--space-4);
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

.article-card-footer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-border-light);
}

/* ----- Buttons ----- */
.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--border-radius-sm);
  font-size: var(--font-size-sm);
  font-weight: 600;
  cursor: pointer;
  transition: all var(--transition-fast);
  border: none;
  text-decoration: none;
  line-height: 1.5;
}

.btn-primary {
  background: var(--color-primary);
  color: white;
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  color: white;
  transform: translateY(-1px);
  box-shadow: 0 4px 12px rgba(99, 102, 241, 0.4);
}

.btn-outline {
  background: transparent;
  color: var(--color-text);
  border: 1px solid var(--color-border);
}

.btn-outline:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.btn-sm {
  padding: var(--space-1) var(--space-3);
  font-size: var(--font-size-xs);
}

/* ----- Sidebar ----- */
.sidebar-card {
  background: var(--color-bg-card);
  border: 1px solid var(--color-border);
  border-radius: var(--border-radius);
  padding: var(--space-6);
  margin-bottom: var(--space-6);
}

.sidebar-card h4 {
  font-size: var(--font-size-lg);
  font-weight: 700;
  margin: 0 0 var(--space-4) 0;
  color: var(--color-text);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.sidebar-card p {
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
  line-height: 1.7;
  margin: 0;
}

/* ----- Article Detail Page ----- */
.article-header {
  text-align: center;
  margin-bottom: var(--space-12);
  padding-bottom: var(--space-8);
  border-bottom: 1px solid var(--color-border);
}

.article-title {
  font-size: var(--font-size-4xl);
  font-weight: 800;
  line-height: 1.2;
  margin: 0 0 var(--space-4) 0;
  letter-spacing: -1px;
}

.article-meta {
  display: flex;
  justify-content: center;
  flex-wrap: wrap;
  gap: var(--space-6);
  font-size: var(--font-size-sm);
  color: var(--color-text-secondary);
}

.article-meta span {
  display: flex;
  align-items: center;
  gap: var(--space-1);
}

.article-content {
  max-width: var(--content-width);
  margin: 0 auto;
  font-size: var(--font-size-lg);
  line-height: 1.9;
  color: var(--color-text);
}

.article-content h2 {
  font-size: var(--font-size-3xl);
  font-weight: 700;
  margin: var(--space-12) 0 var(--space-4);
  padding-bottom: var(--space-2);
  border-bottom: 2px solid var(--color-border-light);
}

.article-content h3 {
  font-size: var(--font-size-2xl);
  font-weight: 600;
  margin: var(--space-8) 0 var(--space-3);
}

.article-content h4 {
  font-size: var(--font-size-xl);
  font-weight: 600;
  margin: var(--space-6) 0 var(--space-2);
}

.article-content p {
  margin: 0 0 var(--space-4);
}

.article-content ul, .article-content ol {
  margin: 0 0 var(--space-4);
  padding-left: var(--space-6);
}

.article-content li {
  margin-bottom: var(--space-2);
}

/* ----- Code Blocks ----- */
.article-content pre {
  background: var(--color-code-bg);
  color: var(--color-code-text);
  border-radius: var(--border-radius-sm);
  padding: var(--space-6);
  overflow-x: auto;
  margin: var(--space-6) 0;
  font-family: var(--font-mono);
  font-size: var(--font-size-sm);
  line-height: 1.6;
  position: relative;
}

.article-content pre::before {
  content: attr(data-lang);
  position: absolute;
  top: var(--space-2);
  right: var(--space-3);
  font-size: var(--font-size-xs);
  color: var(--color-text-muted);
  text-transform: uppercase;
  letter-spacing: 0.5px;
}

.article-content code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--color-bg-alt);
  padding: 2px 6px;
  border-radius: 4px;
}

.article-content pre code {
  background: none;
  padding: 0;
  border-radius: 0;
}

/* ----- Blockquotes ----- */
.article-content blockquote {
  border-left: 4px solid var(--color-blockquote-border);
  background: var(--color-blockquote-bg);
  margin: var(--space-6) 0;
  padding: var(--space-4) var(--space-6);
  border-radius: 0 var(--border-radius-sm) var(--border-radius-sm) 0;
  color: var(--color-text-secondary);
  font-style: italic;
}

.article-content blockquote p {
  margin: 0;
}

/* ----- Images in Articles ----- */
.article-content img {
  border-radius: var(--border-radius-sm);
  margin: var(--space-6) 0;
  box-shadow: 0 4px 20px var(--color-shadow);
}

/* ----- Tables in Articles ----- */
.article-content table {
  width: 100%;
  border-collapse: collapse;
  margin: var(--space-6) 0;
  font-size: var(--font-size-sm);
}

.article-content th,
.article-content td {
  padding: var(--space-3) var(--space-4);
  text-align: left;
  border: 1px solid var(--color-border);
}

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

.article-content tr:nth-child(even) {
  background: var(--color-bg-alt);
}

/* ----- Article Navigation ----- */
.article-nav {
  max-width: var(--content-width);
  margin: var(--space-12) auto 0;
  padding-top: var(--space-8);
  border-top: 1px solid var(--color-border);
  display: flex;
  justify-content: space-between;
  gap: var(--space-4);
}

/* ----- Footer ----- */
.blog-footer {
  background: var(--color-footer-bg);
  color: var(--color-footer-text);
  padding: var(--space-12) var(--space-6);
  text-align: center;
  font-size: var(--font-size-sm);
}

.blog-footer a {
  color: var(--color-primary-light);
}

.blog-footer a:hover {
  color: var(--color-primary);
  text-decoration: underline;
}

.blog-footer p {
  margin: var(--space-2) 0;
}

/* ----- Tags / Categories ----- */
.tag {
  display: inline-flex;
  align-items: center;
  padding: 2px 10px;
  background: var(--color-bg-alt);
  border: 1px solid var(--color-border);
  border-radius: 20px;
  font-size: var(--font-size-xs);
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
}

.tag:hover {
  background: var(--color-primary);
  color: white;
  border-color: var(--color-primary);
}

/* ----- Empty State ----- */
.empty-state {
  text-align: center;
  padding: var(--space-16) var(--space-6);
  color: var(--color-text-secondary);
}

.empty-state i {
  font-size: 3rem;
  margin-bottom: var(--space-4);
  opacity: 0.3;
}

/* ----- Alerts / Messages ----- */
.alert {
  padding: var(--space-4) var(--space-6);
  border-radius: var(--border-radius-sm);
  margin-bottom: var(--space-6);
  font-size: var(--font-size-sm);
}

.alert-danger {
  background: #fef2f2;
  color: #991b1b;
  border: 1px solid #fecaca;
}

.alert-info {
  background: #eff6ff;
  color: #1e40af;
  border: 1px solid #bfdbfe;
}

.alert-warning {
  background: #fffbeb;
  color: #92400e;
  border: 1px solid #fde68a;
}

[data-theme="dark"] .alert-danger {
  background: #451a1a;
  color: #fca5a5;
  border-color: #7f1d1d;
}

[data-theme="dark"] .alert-info {
  background: #172554;
  color: #93c5fd;
  border-color: #1e3a5f;
}

[data-theme="dark"] .alert-warning {
  background: #451a03;
  color: #fcd34d;
  border-color: #78350f;
}

/* ----- Loading Animation ----- */
@keyframes fadeInUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.animate-in {
  animation: fadeInUp 0.5s ease forwards;
}

.animate-in:nth-child(2) { animation-delay: 0.1s; }
.animate-in:nth-child(3) { animation-delay: 0.2s; }
.animate-in:nth-child(4) { animation-delay: 0.3s; }
.animate-in:nth-child(5) { animation-delay: 0.4s; }

/* ----- Responsive ----- */
@media (max-width: 768px) {
  .blog-header-inner {
    flex-direction: column;
    gap: var(--space-3);
    text-align: center;
  }

  .blog-header-logo {
    font-size: var(--font-size-xl);
  }

  .blog-main {
    padding: var(--space-4) var(--space-4);
  }

  .article-card {
    padding: var(--space-4);
  }

  .article-card-title {
    font-size: var(--font-size-xl);
  }

  .article-card-meta {
    font-size: var(--font-size-xs);
    gap: var(--space-2);
  }

  .article-title {
    font-size: var(--font-size-2xl);
  }

  .article-content {
    font-size: var(--font-size-base);
  }

  .article-meta {
    gap: var(--space-3);
    font-size: var(--font-size-xs);
  }

  .article-nav {
    flex-direction: column;
    align-items: center;
  }
}

/* ----- Print ----- */
@media print {
  .blog-header { position: static; }
  #reading-progress { display: none; }
  .theme-toggle { display: none; }
  .article-card { break-inside: avoid; }
}