/**
 * Modern Theme for 钰博的博客
 * Progressive enhancement layer for contemporary design
 * Compatible with GitHub Pages (vanilla CSS only)
 * Design System: Magazine/Blog optimized (UI/UX Pro Max)
 */

/* ==========================================
   Google Fonts - Optimized for Readability
   ========================================== */

@import url('https://fonts.googleapis.com/css2?family=Lexend:wght@300;400;500;600;700&family=Source+Sans+3:wght@300;400;500;600;700&display=swap');

/* ==========================================
   CSS Custom Properties (Design Tokens)
   ========================================== */

:root {
  /* Magazine/Blog Color Palette - Optimized for editorial content */
  --color-primary: #3B82F6;        /* Clear blue - for links, title emphasis */
  --color-primary-dark: #2563EB;   /* Darker blue - for hover states */
  --color-primary-light: #60A5FA;  /* Light blue - for secondary elements */
  --color-accent: #F97316;         /* Orange - for CTA buttons */
  --color-accent-dark: #EA580C;    /* Darker orange - for CTA hover */

  /* Editorial Neutral Colors */
  --color-gray-50: #F8FAFC;
  --color-gray-100: #F1F5F9;
  --color-gray-200: #E2E8F0;
  --color-gray-300: #CBD5E1;
  --color-gray-400: #94A3B8;
  --color-gray-500: #64748B;
  --color-gray-600: #475569;
  --color-gray-700: #334155;
  --color-gray-800: #1E293B;
  --color-gray-900: #0F172A;

  /* Text Colors - WCAG AA compliant */
  --color-text-primary: #1E293B;   /* slate-800 - 4.5:1 contrast ratio */
  --color-text-secondary: #475569; /* slate-600 - enhanced readability */
  --color-text-muted: #64748B;     /* slate-500 - for meta info */
  --color-link: #3B82F6;
  --color-link-hover: #2563EB;

  /* Background Colors */
  --color-bg: #F8FAFC;             /* Soft gray - reduced eye strain */
  --color-surface: #F1F5F9;
  --color-card: #FFFFFF;
  --color-code-bg: #F1F5F9;

  /* Typography - Optimized for Chinese & English readability */
  --font-size-base: 17px;
  --line-height-base: 1.8;
  --line-height-heading: 1.3;
  /* Corporate Trust pairing: Lexend (headings) + Source Sans 3 (body) */
  --font-family-heading: 'Lexend', -apple-system, BlinkMacSystemFont, "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --font-family-base: 'Source Sans 3', -apple-system, BlinkMacSystemFont, "PingFang SC", "Noto Sans SC", "Microsoft YaHei", sans-serif;
  --font-family-code: "SF Mono", Monaco, "Cascadia Code", "Roboto Mono", Consolas, "Courier New", monospace;

  /* Font Sizes (Modular Scale 1.25) */
  --text-xs: 0.75rem;    /* 12px */
  --text-sm: 0.875rem;   /* 14px */
  --text-base: 1rem;     /* 17px */
  --text-lg: 1.125rem;   /* 19px */
  --text-xl: 1.25rem;    /* 21px */
  --text-2xl: 1.563rem;  /* 26px */
  --text-3xl: 1.953rem;  /* 33px */
  --text-4xl: 2.441rem;  /* 41px */
  --text-5xl: 3.052rem;  /* 51px */

  /* Spacing Scale */
  --space-1: 0.25rem;   /* 4px */
  --space-2: 0.5rem;    /* 8px */
  --space-3: 0.75rem;   /* 12px */
  --space-4: 1rem;      /* 17px */
  --space-5: 1.25rem;   /* 21px */
  --space-6: 1.5rem;    /* 25px */
  --space-8: 2rem;      /* 34px */
  --space-10: 2.5rem;   /* 42px */
  --space-12: 3rem;     /* 51px */
  --space-16: 4rem;     /* 68px */
  --space-20: 5rem;     /* 85px */
  --space-24: 6rem;     /* 102px */

  /* Layout */
  --content-width: 680px;
  --container-width: 1280px;
  --sidebar-width: 280px;
  --nav-height: 64px;

  /* Shadows */
  --shadow-xs: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
  --shadow-sm: 0 1px 3px 0 rgba(0, 0, 0, 0.1), 0 1px 2px -1px rgba(0, 0, 0, 0.1);
  --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
  --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  --shadow-xl: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 8px 10px -6px rgba(0, 0, 0, 0.1);

  /* Border Radius */
  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 16px;
  --radius-xl: 24px;
  --radius-full: 9999px;

  /* Transitions */
  --transition-fast: 150ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-base: 250ms cubic-bezier(0.4, 0, 0.2, 1);
  --transition-slow: 350ms cubic-bezier(0.4, 0, 0.2, 1);
}

/* ==========================================
   Base Typography
   ========================================== */

html {
  font-size: var(--font-size-base);
  line-height: var(--line-height-base);
}

body {
  font-family: var(--font-family-base);
  color: var(--color-text-primary);
  background-color: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* Improved heading hierarchy */
h1, h2, h3, h4, h5, h6 {
  font-family: var(--font-family-heading);
  font-weight: 700;
  line-height: var(--line-height-heading);
  letter-spacing: -0.02em;
  color: var(--color-text-primary);
  margin-top: 0;
}

h1 { font-size: var(--text-5xl); margin-bottom: var(--space-6); }
h2 { font-size: var(--text-4xl); margin-bottom: var(--space-5); margin-top: var(--space-12); }
h3 { font-size: var(--text-3xl); margin-bottom: var(--space-4); margin-top: var(--space-10); }
h4 { font-size: var(--text-2xl); margin-bottom: var(--space-4); margin-top: var(--space-8); }
h5 { font-size: var(--text-xl); margin-bottom: var(--space-3); margin-top: var(--space-6); }
h6 { font-size: var(--text-base); margin-bottom: var(--space-3); margin-top: var(--space-6); font-weight: 600; }

/* Responsive heading sizes */
@media (max-width: 768px) {
  h1 { font-size: var(--text-4xl); }
  h2 { font-size: var(--text-3xl); }
  h3 { font-size: var(--text-2xl); }
}

/* Paragraphs and content */
p {
  margin-bottom: 1.75rem;
  color: var(--color-text-primary);
}

/* Links */
a {
  color: var(--color-link);
  text-decoration: none;
  transition: color var(--transition-fast);
}

a:hover {
  color: var(--color-link-hover);
}

.post-container a:not(.btn) {
  border-bottom: 1px solid rgba(37, 99, 235, 0.3);
}

.post-container a:not(.btn):hover {
  border-bottom-color: var(--color-link-hover);
}

/* Lists */
ul, ol {
  margin-bottom: 1.75rem;
}

li {
  margin-bottom: 0.5rem;
}

/* Code */
code {
  font-family: var(--font-family-code);
  font-size: 0.9em;
  background: var(--color-code-bg);
  padding: 0.2em 0.4em;
  border-radius: var(--radius-sm);
  color: var(--color-text-primary);
}

pre {
  background: var(--color-code-bg);
  border-radius: var(--radius-md);
  padding: var(--space-6);
  overflow-x: auto;
  margin-bottom: 1.75rem;
  line-height: 1.6;
  border: 1px solid var(--color-gray-200);
}

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

/* Blockquotes */
blockquote {
  border-left: 4px solid var(--color-primary);
  background: var(--color-surface);
  padding: var(--space-6);
  margin: var(--space-8) 0;
  border-radius: var(--radius-md);
  font-style: normal;
  color: var(--color-text-secondary);
}

blockquote p:last-child {
  margin-bottom: 0;
}

/* ==========================================
   Modern Components
   ========================================== */

/* Navigation Bar - Swiss Modernism inspired */
.navbar-custom {
  background: rgba(255, 255, 255, 0.85);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-gray-200);
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.05);
  transition: all var(--transition-base);
}

.navbar-custom.is-fixed {
  background: rgba(255, 255, 255, 0.90);
  box-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.08);
}

/* Navigation Links - Light Mode */
.navbar-custom .nav > li > a {
  color: var(--color-text-primary);
  font-weight: 500;
  transition: color var(--transition-fast);
}

.navbar-custom .nav > li > a:hover,
.navbar-custom .nav > li > a:focus {
  color: var(--color-primary);
  background: transparent;
}

.navbar-custom .navbar-brand {
  color: var(--color-text-primary);
  font-weight: 700;
  transition: color var(--transition-fast);
}

.navbar-custom .navbar-brand:hover {
  color: var(--color-primary);
}

/* Mobile Menu Toggle */
.navbar-custom .navbar-toggle {
  border-color: var(--color-gray-300);
}

.navbar-custom .navbar-toggle .icon-bar {
  background-color: var(--color-text-primary);
}

.navbar-custom .navbar-toggle:hover,
.navbar-custom .navbar-toggle:focus {
  background-color: var(--color-gray-100);
  border-color: var(--color-primary);
}

/* Post Cards - Magazine/Blog optimized design */
.post-preview {
  background: var(--color-card);
  border-radius: var(--radius-lg);
  padding: var(--space-12) var(--space-10);
  margin-bottom: var(--space-12);
  box-shadow: 0 1px 3px 0 rgba(0, 0, 0, 0.08);
  transition: all 250ms cubic-bezier(0.4, 0, 0.2, 1);
  border: 1px solid var(--color-gray-200);
  position: relative;
  overflow: hidden;
}

/* Subtle accent on hover - avoid layout shift */
.post-preview::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  width: 4px;
  height: 100%;
  background: var(--color-primary);
  transform: scaleY(0);
  transition: transform 250ms cubic-bezier(0.4, 0, 0.2, 1);
  transform-origin: bottom;
}

.post-preview:hover::before {
  transform: scaleY(1);
  transform-origin: top;
}

.post-preview:hover {
  box-shadow: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -4px rgba(0, 0, 0, 0.1);
  transform: translateY(-4px);
  border-color: var(--color-gray-300);
}

.post-title {
  font-size: var(--text-4xl);
  font-weight: 700;
  line-height: 1.2;
  margin-bottom: var(--space-5);
  letter-spacing: -0.03em;
  color: var(--color-text-primary);
}

@media (max-width: 768px) {
  .post-title {
    font-size: var(--text-3xl);
  }
}

.post-subtitle {
  color: var(--color-text-secondary);
  font-size: var(--text-xl);
  margin-bottom: var(--space-6);
  line-height: 1.5;
  font-weight: 400;
}

.post-meta {
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  margin-top: var(--space-6);
  padding-top: var(--space-4);
  border-top: 1px solid var(--color-gray-100);
}

.post-content-preview {
  color: var(--color-text-secondary);
  line-height: 1.9;
  margin-top: var(--space-6);
  font-size: var(--text-lg);
  letter-spacing: 0.01em;
}

/* Wider content container for homepage */
.postlist-container {
  max-width: 900px;
  margin: 0 auto;
  padding-top: var(--space-12);
  padding-bottom: var(--space-16);
}

@media (min-width: 1200px) {
  .postlist-container {
    max-width: 1000px;
  }
}

@media (max-width: 768px) {
  .postlist-container {
    padding-top: var(--space-8);
    padding-bottom: var(--space-12);
  }
}

@media (max-width: 768px) {
  .post-preview {
    padding: var(--space-8) var(--space-6);
    margin-bottom: var(--space-8);
  }
}

/* Hide HR separators on homepage - cards provide enough separation */
.postlist-container > hr {
  display: none;
}

/* Tags */
.tags a, .tag {
  display: inline-block;
  background: var(--color-surface);
  color: var(--color-text-secondary);
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-sm);
  font-size: var(--text-sm);
  margin-right: var(--space-2);
  margin-bottom: var(--space-2);
  transition: all var(--transition-fast);
  border: 1px solid var(--color-gray-200);
}

.tags a:hover, .tag:hover {
  background: var(--color-primary);
  color: white;
  border-color: var(--color-primary);
  text-decoration: none;
  transform: translateY(-1px);
}

/* Header - More Spacious */
.intro-header {
  background-size: cover;
  background-position: center;
  position: relative;
  margin-bottom: var(--space-16);
  min-height: 400px;
}

.intro-header::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background: linear-gradient(to bottom, rgba(0,0,0,0.3), rgba(0,0,0,0.6));
  z-index: 1;
}

.intro-header .container {
  position: relative;
  z-index: 2;
  padding-top: var(--space-20);
  padding-bottom: var(--space-20);
}

.site-heading h1,
.post-heading h1 {
  color: white;
  text-shadow: 0 3px 6px rgba(0,0,0,0.4);
  font-size: 3.5rem;
  font-weight: 800;
  margin-bottom: var(--space-6);
  letter-spacing: -0.03em;
}

@media (max-width: 768px) {
  .intro-header {
    min-height: 300px;
  }

  .intro-header .container {
    padding-top: var(--space-12);
    padding-bottom: var(--space-12);
  }

  .site-heading h1,
  .post-heading h1 {
    font-size: var(--text-3xl);
  }
}

.site-heading .subheading,
.post-heading .subheading {
  color: rgba(255,255,255,0.95);
  font-size: var(--text-2xl);
  font-weight: 300;
  text-shadow: 0 2px 4px rgba(0,0,0,0.3);
  line-height: 1.6;
}

@media (max-width: 768px) {
  .site-heading .subheading,
  .post-heading .subheading {
    font-size: var(--text-lg);
  }
}

/* Sidebar */
.sidebar-container {
  padding-top: var(--space-8);
}

.sidebar-container h5 {
  font-size: var(--text-lg);
  font-weight: 700;
  margin-bottom: var(--space-4);
  color: var(--color-text-primary);
}

.short-about {
  margin-top: var(--space-6);
}

.short-about img {
  border-radius: var(--radius-full);
  width: 120px;
  height: 120px;
  object-fit: cover;
  margin-bottom: var(--space-4);
  border: 3px solid var(--color-gray-100);
  transition: all var(--transition-base);
}

.short-about img:hover {
  transform: scale(1.05);
  border-color: var(--color-primary);
}

/* Buttons - CTA optimized */
.btn {
  padding: var(--space-3) var(--space-6);
  border-radius: var(--radius-md);
  font-weight: 500;
  transition: all 250ms cubic-bezier(0.4, 0, 0.2, 1);
  border: none;
  font-family: var(--font-family-heading);
}

.btn-primary {
  background: var(--color-accent);
  color: white;
  box-shadow: 0 2px 4px rgba(249, 115, 22, 0.2);
}

.btn-primary:hover {
  background: var(--color-accent-dark);
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(249, 115, 22, 0.3);
  color: white;
}

/* Pagination - Clean & Modern */
.pager {
  margin: var(--space-16) 0;
  font-size: var(--text-lg);
}

.pager li > a,
.pager li > span {
  background: var(--color-card);
  border: 2px solid var(--color-gray-200);
  border-radius: var(--radius-lg);
  color: var(--color-text-primary);
  padding: var(--space-6) var(--space-10);
  transition: all 250ms cubic-bezier(0.4, 0, 0.2, 1);
  font-weight: 500;
  display: inline-block;
  min-width: 160px;
  text-align: center;
  font-family: var(--font-family-heading);
}

.pager li > a:hover {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: white;
  transform: translateY(-2px);
  box-shadow: 0 4px 8px rgba(59, 130, 246, 0.3);
  text-decoration: none;
}

@media (max-width: 768px) {
  .pager li > a,
  .pager li > span {
    padding: var(--space-4) var(--space-6);
    min-width: 120px;
    font-size: var(--text-base);
  }
}

/* Footer */
footer {
  background: var(--color-surface);
  border-top: 1px solid var(--color-gray-200);
  padding: var(--space-12) 0;
  margin-top: var(--space-16);
}

/* Table of Contents */
.side-catalog {
  position: sticky;
  top: calc(var(--nav-height) + var(--space-6));
}

.catalog-body {
  border-left: 2px solid var(--color-gray-200);
  padding-left: var(--space-4);
}

.catalog-body li {
  margin-bottom: var(--space-2);
}

.catalog-body a {
  color: var(--color-text-secondary);
  font-size: var(--text-sm);
  transition: color var(--transition-fast);
}

.catalog-body a:hover,
.catalog-body a.active {
  color: var(--color-primary);
}

/* ==========================================
   Utility Classes
   ========================================== */

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

.text-secondary {
  color: var(--color-text-secondary);
}

.rounded {
  border-radius: var(--radius-md);
}

.shadow {
  box-shadow: var(--shadow-md);
}

/* ==========================================
   Responsive Utilities
   ========================================== */

@media (max-width: 768px) {
  :root {
    --font-size-base: 16px;
  }

  .post-preview {
    padding: var(--space-6);
    margin-bottom: var(--space-6);
  }

  .intro-header {
    min-height: 250px;
  }
}

/* ==========================================
   Accessibility & UX Best Practices
   ========================================== */

/* Respect user's motion preferences (WCAG 2.1) */
@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}

/* Enhanced focus states for keyboard navigation */
a:focus-visible,
button:focus-visible,
.btn:focus-visible {
  outline: 2px solid var(--color-primary);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}

/* Cursor pointer for interactive elements */
.post-preview,
.tags a,
.tag,
.btn,
button,
.navbar-toggle {
  cursor: pointer;
}

/* Smooth hover transitions (200-300ms optimal) */
.post-preview,
.tags a,
.tag,
.btn,
.pager li > a,
.navbar-custom .nav > li > a,
.short-about img {
  transition-duration: 250ms;
  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
}

/* Prevent layout shift on hover (no scale transforms) */
.post-preview:hover {
  /* Use shadow and border instead of scale */
  transform: translateY(-3px); /* Vertical lift is acceptable */
}

/* ==========================================
   Print Styles
   ========================================== */

@media print {
  .navbar-custom,
  .sidebar-container,
  footer,
  .pager {
    display: none !important;
  }

  body {
    font-size: 12pt;
    line-height: 1.5;
  }

  a {
    text-decoration: underline;
  }
}