:root {
  /* Fonts */
  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  --font-mono: "SF Mono", "Monaco", "Inconsolata", "Fira Code", "Consolas", monospace;

  /* Colors - Professional Navy Palette */
  --color-bg: #ffffff;
  --color-bg-subtle: #f8f9fa;
  --color-text: #1a202c;
  --color-text-muted: #64748b;
  --color-primary: #1e3a8a;
  --color-accent: #3b82f6;
  --color-accent-hover: #2563eb;
  --color-border: #e2e8f0;
  --color-code-bg: #f1f5f9;
  --color-shadow: rgba(15, 23, 42, 0.08);

  /* Spacing */
  --max-width: 720px;
  --spacing-sm: 0.5rem;
  --spacing-md: 1rem;
  --spacing-lg: 1.5rem;
  --spacing-xl: 2.5rem;
  --spacing-2xl: 3.5rem;

  /* Effects */
  --transition: all 0.2s ease;
  --shadow-sm: 0 1px 3px 0 var(--color-shadow);
  --shadow-md: 0 4px 6px -1px var(--color-shadow);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --color-bg: #0f172a;
    --color-bg-subtle: #1e293b;
    --color-text: #e2e8f0;
    --color-text-muted: #94a3b8;
    --color-primary: #3b82f6;
    --color-accent: #60a5fa;
    --color-accent-hover: #93c5fd;
    --color-border: #334155;
    --color-code-bg: #1e293b;
    --color-shadow: rgba(0, 0, 0, 0.3);
  }
}

/* Explicit dark theme (manual toggle) */
[data-theme="dark"] {
  --color-bg: #0f172a;
  --color-bg-subtle: #1e293b;
  --color-text: #e2e8f0;
  --color-text-muted: #94a3b8;
  --color-primary: #3b82f6;
  --color-accent: #60a5fa;
  --color-accent-hover: #93c5fd;
  --color-border: #334155;
  --color-code-bg: #1e293b;
  --color-shadow: rgba(0, 0, 0, 0.3);
}

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

html {
  font-size: 18px;
  line-height: 1.7;
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--spacing-lg);
  width: 100%;
}

/* Header */
.site-header {
  padding: var(--spacing-xl) 0;
  border-bottom: 1px solid var(--color-border);
  background: var(--color-bg);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: blur(10px);
}

.site-header .container {
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.site-title {
  font-size: 1.1rem;
  font-weight: 600;
  color: var(--color-text);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 0.75rem;
  transition: var(--transition);
}

.site-title:hover {
  color: var(--color-primary);
}

.site-title-text {
  font-size: 2.25rem;
  font-weight: 700;
  background: linear-gradient(135deg, #1e3a8a 0%, #3b82f6 50%, #60a5fa 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
  letter-spacing: -0.02em;
}

.site-title:hover .site-title-text {
  background: linear-gradient(135deg, #3b82f6 0%, #60a5fa 50%, #93c5fd 100%);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.site-logo {
  width: 42px;
  height: 42px;
  border-radius: 10px;
  box-shadow: var(--shadow-sm);
}

.site-nav {
  display: flex;
  gap: var(--spacing-lg);
}

.site-nav a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: var(--transition);
  position: relative;
  padding: 0.5rem 0;
}

.site-nav a:hover,
.site-nav a.active {
  color: var(--color-primary);
}

.site-nav a::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-primary);
  transition: width 0.3s ease;
}

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

/* Theme toggle */
.theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  color: var(--color-text-muted);
  transition: var(--transition);
  display: flex;
  align-items: center;
  justify-content: center;
  border-radius: 8px;
}

.theme-toggle:hover {
  color: var(--color-primary);
  background: var(--color-bg-subtle);
}

.theme-toggle .icon-sun {
  display: block;
}

.theme-toggle .icon-moon {
  display: none;
}

[data-theme="dark"] .theme-toggle .icon-sun {
  display: none;
}

[data-theme="dark"] .theme-toggle .icon-moon {
  display: block;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .theme-toggle .icon-sun {
    display: none;
  }
  :root:not([data-theme="light"]) .theme-toggle .icon-moon {
    display: block;
  }
}

/* Reading progress bar */
.reading-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 0%;
  height: 3px;
  background: linear-gradient(90deg, #1e3a8a 0%, #3b82f6 50%, #60a5fa 100%);
  z-index: 1000;
  transition: width 0.1s ease-out;
}

.post .post-header {
  margin-top: var(--spacing-xl);
}

/* Reading time */
.reading-time {
  color: var(--color-text-muted);
  font-size: 0.85rem;
}

.post-meta .reading-time::before {
  content: "·";
  margin-right: 0.5rem;
}

.post-item-meta {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  font-size: 0.85rem;
  color: var(--color-text-muted);
  margin-bottom: 0.5rem;
  font-weight: 500;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.post-item-meta .reading-time {
  text-transform: none;
  letter-spacing: normal;
}

/* Main content */
main {
  flex: 1;
  padding: var(--spacing-2xl) 0;
}

/* Homepage */
.home .intro {
  margin-bottom: var(--spacing-lg);
  padding: var(--spacing-xl) 0;
}

.home .intro-text {
  font-size: 1.1rem;
  line-height: 1.6;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
}

.home .intro-text:first-child {
  font-size: 1.25rem;
  font-weight: 500;
  margin-bottom: var(--spacing-sm);
}

.wave {
  display: inline-block;
  animation: wave 2.5s ease-in-out infinite;
  transform-origin: 70% 70%;
}

@keyframes wave {
  0%, 100% { transform: rotate(0deg); }
  10% { transform: rotate(14deg); }
  20% { transform: rotate(-8deg); }
  30% { transform: rotate(14deg); }
  40% { transform: rotate(-4deg); }
  50% { transform: rotate(10deg); }
  60%, 100% { transform: rotate(0deg); }
}

.home .intro-link {
  font-size: 0.9rem;
  color: var(--color-accent);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
}

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

.recent-posts h2 {
  font-size: 1.25rem;
  color: var(--color-text);
  margin-bottom: var(--spacing-lg);
  font-weight: 600;
  letter-spacing: -0.01em;
}

.view-all {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: var(--spacing-lg);
  color: var(--color-accent);
  text-decoration: none;
  font-size: 0.95rem;
  font-weight: 500;
  transition: var(--transition);
}

.view-all:hover {
  color: var(--color-accent-hover);
  transform: translateX(4px);
}

/* Post list */
.post-list {
  list-style: none;
}

.post-item {
  margin-bottom: var(--spacing-lg);
  background: var(--color-bg-subtle);
  border: 1px solid var(--color-border);
  border-radius: 10px;
  transition: var(--transition);
}

.post-item:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-2px);
  border-color: var(--color-primary);
}

.post-item-link {
  display: block;
  padding: var(--spacing-lg);
  color: var(--color-text);
  text-decoration: none;
}

.post-item time {
  font-size: inherit;
  color: inherit;
}

.post-item-title {
  color: var(--color-text);
  font-weight: 600;
  font-size: 1.15rem;
  line-height: 1.4;
  transition: var(--transition);
  margin-bottom: 0.5rem;
}

.post-item:hover .post-item-title {
  color: var(--color-accent);
}

.post-excerpt {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  line-height: 1.6;
  margin-top: 0.5rem;
}

/* Single post */
.post-header {
  margin-bottom: var(--spacing-2xl);
  padding-bottom: var(--spacing-lg);
  border-bottom: 2px solid var(--color-border);
}

.post-header h1 {
  font-size: 2.5rem;
  line-height: 1.3;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 1rem;
  color: var(--color-text);
}

.post-meta {
  color: var(--color-text-muted);
  font-size: 0.9rem;
  display: flex;
  align-items: center;
  gap: 1rem;
}

.post-tags {
  display: flex;
  gap: 0.5rem;
  flex-wrap: wrap;
}

.post-tags a {
  color: var(--color-accent);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
  padding: 0.25rem 0.75rem;
  background: var(--color-bg-subtle);
  border-radius: 6px;
  font-size: 0.85rem;
}

.post-tags a:hover {
  background: var(--color-accent);
  color: white;
}

.post-content {
  font-size: 1.05rem;
  line-height: 1.75;
}

.post-content h2 {
  font-size: 1.75rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 2.5rem 0 1.25rem;
  color: var(--color-text);
}

.post-content h3 {
  font-size: 1.35rem;
  font-weight: 600;
  margin: 2rem 0 1rem;
  color: var(--color-text);
}

.post-content p {
  margin-bottom: 1.5rem;
}

.post-content a {
  color: var(--color-accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: var(--transition);
}

.post-content a:hover {
  color: var(--color-accent-hover);
  border-bottom-color: var(--color-accent-hover);
}

.post-content ul,
.post-content ol {
  margin: 0 0 1.5rem 1.5rem;
}

.post-content li {
  margin-bottom: 0.75rem;
}

.post-content strong {
  font-weight: 600;
  color: var(--color-text);
}

.post-content blockquote {
  border-left: 4px solid var(--color-primary);
  padding-left: 1.5rem;
  margin: 2rem 0;
  color: var(--color-text-muted);
  font-style: italic;
  font-size: 1.1rem;
}

.post-content code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  background: var(--color-code-bg);
  padding: 0.25em 0.5em;
  border-radius: 4px;
  border: 1px solid var(--color-border);
  color: var(--color-primary);
}

.post-content pre {
  background: var(--color-code-bg);
  padding: 1.5rem;
  border-radius: 10px;
  overflow-x: auto;
  margin: 2rem 0;
  border: 1px solid var(--color-border);
  box-shadow: var(--shadow-sm);
}

.post-content pre code {
  background: none;
  padding: 0;
  border: none;
  color: var(--color-text);
  font-size: 0.9rem;
}

.post-content img {
  max-width: 100%;
  height: auto;
  border-radius: 10px;
  margin: 2rem 0;
  box-shadow: var(--shadow-md);
}

.post-content hr {
  border: none;
  border-top: 2px solid var(--color-border);
  margin: 3rem 0;
}

/* Post navigation */
.post-nav {
  display: flex;
  justify-content: space-between;
  margin-top: var(--spacing-2xl);
  margin-bottom: var(--spacing-2xl);
  padding-top: var(--spacing-lg);
  border-top: 1px solid var(--color-border);
  font-size: 0.95rem;
  gap: var(--spacing-md);
}

.post-nav a {
  color: var(--color-accent);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
  padding: 0.75rem 1rem;
  background: var(--color-bg-subtle);
  border-radius: 8px;
  border: 1px solid var(--color-border);
}

.post-nav a:hover {
  background: var(--color-accent);
  color: white;
  border-color: var(--color-accent);
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.post-nav .next {
  margin-left: auto;
}

/* Footer */
.site-footer {
  padding: var(--spacing-xl) 0;
  border-top: 1px solid var(--color-border);
  margin-top: auto;
  background: var(--color-bg-subtle);
}

.footer-content {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.9rem;
  color: var(--color-text-muted);
}

.social-links {
  display: flex;
  gap: var(--spacing-lg);
}

.social-links a {
  color: var(--color-text-muted);
  text-decoration: none;
  font-weight: 500;
  transition: var(--transition);
}

.social-links a:hover {
  color: var(--color-primary);
}

/* Newsletter signup */
.newsletter {
  margin-top: var(--spacing-2xl);
  padding: var(--spacing-xl);
  background: var(--color-bg-subtle);
  border-radius: 12px;
  border: 1px solid var(--color-border);
  text-align: center;
}

.newsletter h3 {
  font-size: 1.25rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-sm);
}

.newsletter p {
  color: var(--color-text-muted);
  font-size: 0.95rem;
  margin-bottom: var(--spacing-lg);
}

.newsletter-form {
  display: flex;
  gap: var(--spacing-sm);
  max-width: 400px;
  margin: 0 auto;
}

.newsletter-form input[type="email"] {
  flex: 1;
  padding: 0.75rem 1rem;
  font-size: 1rem;
  border: 1px solid var(--color-border);
  border-radius: 8px;
  background: var(--color-bg);
  color: var(--color-text);
  transition: var(--transition);
}

.newsletter-form input[type="email"]:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.1);
}

.newsletter-form input[type="email"]::placeholder {
  color: var(--color-text-muted);
}

.newsletter-form button {
  padding: 0.75rem 1.5rem;
  font-size: 1rem;
  font-weight: 600;
  color: white;
  background: linear-gradient(135deg, #1e3a8a 0%, #3b82f6 100%);
  border: none;
  border-radius: 8px;
  cursor: pointer;
  transition: var(--transition);
}

.newsletter-form button:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

/* Footer newsletter */
.footer-newsletter {
  text-align: center;
  padding-bottom: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
  border-bottom: 1px solid var(--color-border);
}

.footer-newsletter h4 {
  font-size: 1rem;
  font-weight: 600;
  color: var(--color-text);
  margin-bottom: var(--spacing-md);
}

.newsletter-form-inline {
  justify-content: center;
}

/* Page content (About, Contact, etc) */
.page h1 {
  font-size: 2.25rem;
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: var(--spacing-xl);
  color: var(--color-text);
}

.page h2 {
  font-size: 1.5rem;
  font-weight: 600;
  margin-top: var(--spacing-xl);
  margin-bottom: var(--spacing-md);
  color: var(--color-text);
}

.page h3 {
  font-size: 1.25rem;
  font-weight: 600;
  margin-top: var(--spacing-lg);
  margin-bottom: var(--spacing-sm);
  color: var(--color-text);
}

.page p {
  margin-bottom: var(--spacing-lg);
  line-height: 1.75;
}

.page a {
  color: var(--color-accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: var(--transition);
  font-weight: 500;
}

.page a:hover {
  color: var(--color-accent-hover);
  border-bottom-color: var(--color-accent-hover);
}

.page ul {
  margin: var(--spacing-lg) 0;
  padding-left: 1.5rem;
}

.page li {
  margin-bottom: 0.5rem;
}

/* Responsive */
@media (max-width: 768px) {
  html {
    font-size: 17px;
  }

  :root {
    --spacing-xl: 2rem;
    --spacing-2xl: 2.5rem;
  }

  .site-header {
    position: relative;
    padding: var(--spacing-lg) 0;
  }

  .site-header .container {
    flex-direction: column;
    align-items: flex-start;
    gap: var(--spacing-md);
  }

  .site-nav {
    gap: var(--spacing-md);
  }

  .home h1 {
    font-size: 1.75rem;
  }

  .post-header h1 {
    font-size: 2rem;
  }

  .post-content h2 {
    font-size: 1.5rem;
  }

  .footer-content {
    flex-direction: column;
    gap: var(--spacing-md);
    text-align: center;
  }

  .social-links {
    gap: var(--spacing-md);
  }

  .post-nav {
    flex-direction: column;
  }

  .post-nav .next {
    margin-left: 0;
  }

  .newsletter-form {
    flex-direction: column;
  }

  .newsletter-form button {
    width: 100%;
  }
}

@media (max-width: 480px) {
  html {
    font-size: 16px;
  }

  .home .intro {
    padding: var(--spacing-lg);
  }

  .post-item {
    padding: var(--spacing-md);
  }
}