/* =============================================
   CSS Custom Properties — Dark Theme
   ============================================= */
:root {
  --bg:           #0d1117;
  --bg-card:      #161b22;
  --bg-hover:     #1c2128;
  --text:         #f0f6fc;
  --text-muted:   #adbac7;
  --accent:       #58a6ff;
  --accent-dim:   #1f6feb;
  --border:       #30363d;
  --border-light: #21262d;
  --green:        #3fb950;
  --radius:       6px;
  --max-width:    960px;
  --font:         system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono:    "SF Mono", "Cascadia Code", "Fira Mono", monospace;
  --transition:   0.15s ease;
}

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

html { scroll-behavior: smooth; }

body {
  font-family: var(--font);
  font-size: 1rem;
  line-height: 1.7;
  background: var(--bg);
  color: var(--text);
  -webkit-font-smoothing: antialiased;
}

img, video { max-width: 100%; display: block; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

ul { list-style: none; }

/* =============================================
   Layout helpers
   ============================================= */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 1.5rem;
}

.section {
  padding: 5rem 0;
}

.bg-card { background: var(--bg-card); }

.section-title {
  font-size: 1.5rem;
  font-weight: 600;
  letter-spacing: -0.01em;
  margin-bottom: 2rem;
  color: var(--text);
}

.section-cta {
  margin-top: 2.5rem;
}

/* =============================================
   Navigation
   ============================================= */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: rgba(13, 17, 23, 0.92);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border-light);
}

.nav {
  display: flex;
  align-items: center;
  height: 60px;
  gap: 2rem;
}

.nav-logo {
  font-size: 1.1rem;
  font-weight: 700;
  color: var(--text);
  letter-spacing: -0.02em;
  flex-shrink: 0;
}
.nav-logo:hover { text-decoration: none; color: var(--accent); }

.nav-menu {
  display: flex;
  align-items: center;
  gap: 0.25rem;
  margin-left: auto;
}

.nav-link {
  font-size: 0.875rem;
  color: var(--text-muted);
  padding: 0.35rem 0.75rem;
  border-radius: var(--radius);
  transition: color var(--transition), background var(--transition);
}
.nav-link:hover { color: var(--text); background: var(--bg-hover); text-decoration: none; }
.nav-link.active { color: var(--text); }

/* Mobile toggle */
.nav-toggle {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.5rem;
  margin-left: auto;
}
.nav-toggle span {
  display: block;
  width: 22px;
  height: 2px;
  background: var(--text);
  border-radius: 2px;
  transition: transform var(--transition), opacity var(--transition);
}

/* =============================================
   Buttons
   ============================================= */
.btn {
  display: inline-block;
  padding: 0.6rem 1.4rem;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 500;
  cursor: pointer;
  transition: opacity var(--transition), transform var(--transition);
}
.btn:hover { opacity: 0.85; transform: translateY(-1px); text-decoration: none; }

.btn-primary {
  background: var(--accent-dim);
  color: #fff;
  border: 1px solid var(--accent);
}

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

/* =============================================
   Hero
   ============================================= */
.hero {
  padding: 6rem 0 5rem;
  border-bottom: 1px solid var(--border-light);
}

.hero-inner {
  max-width: 640px;
}

.hero-eyebrow {
  font-size: 0.875rem;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.5rem;
}

.hero-name {
  font-size: clamp(2.5rem, 6vw, 3.5rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: 0.75rem;
  color: var(--text);
}

.hero-tagline {
  font-size: 1.25rem;
  color: var(--accent);
  font-weight: 500;
  margin-bottom: 1.25rem;
}

.hero-description {
  color: var(--text-muted);
  font-size: 1.05rem;
  max-width: 520px;
  margin-bottom: 2rem;
}

.hero-cta {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

/* =============================================
   Link arrow
   ============================================= */
.link-arrow {
  font-size: 0.875rem;
  color: var(--accent);
  font-weight: 500;
}
.link-arrow:hover { text-decoration: underline; }

/* =============================================
   About teaser
   ============================================= */
.section-about-teaser .teaser-text {
  color: var(--text-muted);
  font-size: 1.05rem;
  max-width: 680px;
  margin-bottom: 1rem;
}

/* =============================================
   Services grid (home teaser)
   ============================================= */
.services-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 1.5rem;
}

.service-card {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: border-color var(--transition), transform var(--transition);
}
.service-card:hover { border-color: var(--accent-dim); transform: translateY(-2px); }

.service-icon {
  font-size: 1.75rem;
  margin-bottom: 0.75rem;
}

.service-card h3 {
  font-size: 1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.service-card p {
  font-size: 0.875rem;
  color: var(--text-muted);
  line-height: 1.6;
}

/* =============================================
   Blog tag filter bar
   ============================================= */
.tag-filter-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 2rem;
}

.tag-filter-btn {
  font-size: 0.75rem;
  font-family: var(--font-mono);
  background: var(--bg-hover);
  color: var(--text-muted);
  border: 1px solid var(--border);
  border-radius: 2rem;
  padding: 0.2rem 0.6rem;
  cursor: pointer;
  transition: color var(--transition), border-color var(--transition), background var(--transition);
}
.tag-filter-btn:hover {
  color: var(--text);
  border-color: var(--accent-dim);
}
.tag-filter-btn.active {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--bg-hover);
}

/* =============================================
   Blog post cards
   ============================================= */
.post-list {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

.post-card {
  position: relative;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  transition: border-color var(--transition);
  cursor: pointer;
}
.post-card:hover { border-color: var(--accent-dim); }

.post-title a::after {
  content: "";
  position: absolute;
  inset: 0;
}

.post-date {
  display: block;
  font-size: 0.8rem;
  color: var(--text-muted);
  margin-bottom: 0.4rem;
  font-family: var(--font-mono);
}

.post-title {
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin-bottom: 0.5rem;
}
.post-title a { color: var(--text); }
.post-title a:hover { color: var(--accent); text-decoration: none; }

.post-summary {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: 0.75rem;
}

/* Tags */
.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.4rem;
  margin-bottom: 0.75rem;
}

.tag {
  font-size: 0.75rem;
  font-family: var(--font-mono);
  background: var(--bg-hover);
  color: var(--text-muted);
  padding: 0.2rem 0.6rem;
  border-radius: 2rem;
  border: 1px solid var(--border);
}

/* =============================================
   Talks & Community section
   ============================================= */
.talks-intro {
  font-size: 0.95rem;
  color: var(--text-muted);
  margin-bottom: 2rem;
  max-width: 600px;
}

.talks-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.25rem;
}

.talk-card {
  display: flex;
  flex-direction: column;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  background: var(--bg-card);
  text-decoration: none;
  transition: border-color var(--transition), transform var(--transition);
}
.talk-card:hover {
  border-color: var(--accent-dim);
  transform: translateY(-2px);
  text-decoration: none;
}

.talk-thumb {
  position: relative;
  aspect-ratio: 16 / 9;
  overflow: hidden;
  background: var(--bg-hover);
}
.talk-thumb img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  display: block;
}

.talk-play {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  color: #fff;
  background: rgba(0, 0, 0, 0.38);
  opacity: 0;
  transition: opacity var(--transition);
}
.talk-card:hover .talk-play { opacity: 1; }

.talk-meta {
  padding: 0.875rem 1rem 1rem;
  flex: 1;
}

.talk-conf {
  display: inline-block;
  font-size: 0.7rem;
  font-family: var(--font-mono);
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 0.4rem;
}

.talk-title {
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text);
  line-height: 1.4;
}

/* =============================================
   Video modal
   ============================================= */
.video-modal {
  display: none;
  position: fixed;
  inset: 0;
  z-index: 500;
  align-items: center;
  justify-content: center;
  padding: 1rem;
}
.video-modal.open { display: flex; }

.video-modal-backdrop {
  position: absolute;
  inset: 0;
  background: rgba(0, 0, 0, 0.88);
}

.video-modal-inner {
  position: relative;
  z-index: 1;
  width: 100%;
  max-width: 900px;
}

.video-modal-close {
  position: absolute;
  top: -2.25rem;
  right: 0;
  background: none;
  border: none;
  color: #fff;
  font-size: 1.5rem;
  line-height: 1;
  cursor: pointer;
  padding: 0.25rem 0.5rem;
  opacity: 0.8;
}
.video-modal-close:hover { opacity: 1; }

.video-modal-player {
  position: relative;
  aspect-ratio: 16 / 9;
  background: #000;
  border-radius: var(--radius);
  overflow: hidden;
}
.video-modal-player iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: none;
}

/* =============================================
   Course section
   ============================================= */
.course-card {
  display: flex;
  align-items: flex-start;
  gap: 1.25rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.75rem;
  transition: border-color var(--transition);
}
.course-card:hover { border-color: var(--accent-dim); }

.course-icon {
  font-size: 2rem;
  flex-shrink: 0;
  line-height: 1;
  margin-top: 0.15rem;
}

.course-content { flex: 1; }

.course-title {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 0.5rem;
}

.course-description {
  font-size: 0.9rem;
  color: var(--text-muted);
  margin-bottom: 1.25rem;
  line-height: 1.6;
}

/* =============================================
   Page layouts (about, services, contact, blog)
   ============================================= */
.main-content { min-height: calc(100vh - 60px - 80px); }

.page-container {
  padding-top: 4rem;
  padding-bottom: 5rem;
}

.page-header {
  margin-bottom: 3rem;
  border-bottom: 1px solid var(--border-light);
  padding-bottom: 2rem;
}

.page-title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  color: var(--text);
}

.page-description {
  margin-top: 1rem;
  color: var(--text-muted);
  font-size: 1.05rem;
}

/* =============================================
   About page
   ============================================= */
.about-body {
  max-width: 680px;
}

.about-body p { margin-bottom: 1.25rem; color: var(--text-muted); }
.about-body h2 { font-size: 1.25rem; font-weight: 600; margin: 2.5rem 0 1rem; color: var(--text); }
.about-body ul { list-style: disc; padding-left: 1.5rem; margin-bottom: 1.25rem; }
.about-body li { margin-bottom: 0.4rem; color: var(--text-muted); }
.about-body strong { color: var(--text); }

/* =============================================
   Services page
   ============================================= */
.services-full {
  display: flex;
  flex-direction: column;
  gap: 3.5rem;
}

.service-item {
  max-width: 720px;
}

.service-item h2 {
  font-size: 1.4rem;
  font-weight: 700;
  margin-bottom: 0.75rem;
  color: var(--text);
}

.service-item > p {
  color: var(--text-muted);
  margin-bottom: 1.25rem;
}

.service-item ul {
  list-style: disc;
  padding-left: 1.25rem;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.service-item ul li {
  font-size: 0.9rem;
  color: var(--text-muted);
}

.service-item p {
  color: var(--text-muted);
  margin-bottom: 1.25rem;
}

.services-cta {
  margin-top: 4rem;
  padding-top: 2.5rem;
  border-top: 1px solid var(--border-light);
  display: flex;
  align-items: center;
  gap: 2rem;
  flex-wrap: wrap;
}

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

/* =============================================
   Contact page
   ============================================= */
.contact-block {
  max-width: 560px;
}

.contact-lead {
  font-size: 1.1rem;
  color: var(--text-muted);
  margin-bottom: 1.75rem;
}

.contact-btn {
  font-size: 1rem;
  margin-bottom: 0.75rem;
}

.contact-email-hint {
  display: block;
  margin-bottom: 2rem;
  font-size: 0.8rem;
  font-family: var(--font-mono);
  color: var(--text-muted);
  user-select: all;
}

.contact-email-hint::before {
  content: attr(data-user) "@" attr(data-domain);
}

.social-cards {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

.social-card {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 1rem 1.25rem;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  text-decoration: none;
  transition: border-color var(--transition), background var(--transition), transform var(--transition);
}

.social-card:hover {
  background: var(--bg-hover);
  text-decoration: none;
  transform: translateX(3px);
}

.social-card--linkedin:hover { border-color: #0a66c2; }
.social-card--github:hover   { border-color: #58a6ff; }

.social-card__logo {
  width: 2rem;
  height: 2rem;
  flex-shrink: 0;
  color: var(--text-muted);
  transition: color var(--transition);
}

.social-card--linkedin:hover .social-card__logo { color: #0a66c2; }
.social-card--github:hover   .social-card__logo { color: var(--accent); }

.social-card__body {
  display: flex;
  flex-direction: column;
  flex: 1;
}

.social-card__name {
  font-weight: 600;
  font-size: 0.95rem;
  color: var(--text);
}

.social-card__handle {
  font-size: 0.8rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
}

.social-card__arrow {
  width: 1rem;
  height: 1rem;
  color: var(--text-muted);
  flex-shrink: 0;
  transition: color var(--transition);
}

.social-card:hover .social-card__arrow { color: var(--text); }

/* =============================================
   Single article (blog post)
   ============================================= */
.single-article {
  max-width: 700px;
}

.article-header {
  margin-bottom: 3rem;
  padding-bottom: 2rem;
  border-bottom: 1px solid var(--border-light);
}

.article-title {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  font-weight: 700;
  letter-spacing: -0.02em;
  margin-bottom: 0.75rem;
}

.article-date {
  display: block;
  font-size: 0.85rem;
  color: var(--text-muted);
  font-family: var(--font-mono);
  margin-bottom: 0.75rem;
}

.article-body { color: var(--text-muted); }
.article-body p { margin-bottom: 1.25rem; }
.article-body h2 { font-size: 1.3rem; font-weight: 600; margin: 2.5rem 0 1rem; color: var(--text); }
.article-body h3 { font-size: 1.1rem; font-weight: 600; margin: 2rem 0 0.75rem; color: var(--text); }
.article-body ul, .article-body ol { padding-left: 1.5rem; margin-bottom: 1.25rem; }
.article-body ul { list-style: disc; }
.article-body ol { list-style: decimal; }
.article-body li { margin-bottom: 0.4rem; }
.article-body a { color: var(--accent); }
.article-body strong { color: var(--text); }
.article-body blockquote {
  border-left: 3px solid var(--accent-dim);
  padding-left: 1rem;
  margin: 1.5rem 0;
  color: var(--text-muted);
  font-style: italic;
}

.article-body code {
  font-family: var(--font-mono);
  font-size: 0.875em;
  background: var(--bg-card);
  border: 1px solid var(--border);
  padding: 0.15em 0.4em;
  border-radius: 3px;
  color: var(--text);
}

.article-body pre {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  overflow-x: auto;
  margin: 1.5rem 0;
}

.article-body pre code {
  background: none;
  border: none;
  padding: 0;
  font-size: 0.875rem;
}

/* =============================================
   Footer
   ============================================= */
.site-footer {
  background: var(--bg-card);
  border-top: 1px solid var(--border-light);
}

.footer-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 80px;
  flex-wrap: wrap;
  gap: 1rem;
}

.footer-copy {
  font-size: 0.8rem;
  color: var(--text-muted);
}

.footer-links {
  display: flex;
  gap: 1.5rem;
}

.footer-links a {
  font-size: 0.8rem;
  color: var(--text-muted);
  transition: color var(--transition);
}
.footer-links a:hover { color: var(--accent); text-decoration: none; }

/* =============================================
   Empty state
   ============================================= */
.empty-state {
  color: var(--text-muted);
  font-style: italic;
}

/* =============================================
   Responsive
   ============================================= */
@media (max-width: 640px) {
  .nav-toggle { display: flex; }
  .nav-menu {
    display: none;
    position: absolute;
    top: 60px;
    left: 0;
    right: 0;
    background: var(--bg-card);
    border-bottom: 1px solid var(--border);
    flex-direction: column;
    padding: 1rem 1.5rem;
    gap: 0.25rem;
  }
  .nav-menu.open { display: flex; }
  .nav-link { padding: 0.6rem 0; font-size: 1rem; }
  .hero { padding: 4rem 0 3rem; }
  .hero-cta { flex-direction: column; }
  .btn { width: 100%; text-align: center; }
  .services-cta { flex-direction: column; align-items: flex-start; }
  .course-card { flex-direction: column; }
  .talks-grid { grid-template-columns: 1fr; }
  .footer-inner { height: auto; padding: 1.5rem 0; }
}

/* =============================================
   Language switcher
   ============================================= */
.lang-switch {
  display: flex;
  align-items: center;
  gap: 0.15rem;
  font-size: 0.75rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  flex-shrink: 0;
}

.lang-item {
  padding: 0.2rem 0.35rem;
  border-radius: var(--radius);
}

.lang-current {
  color: var(--text);
}

.lang-link {
  color: var(--text-muted);
  text-decoration: none;
  transition: color var(--transition);
}

.lang-link:hover {
  color: var(--text);
  text-decoration: none;
}

.lang-switch .lang-item + .lang-item::before {
  content: "/";
  color: var(--border);
  margin-right: 0.15rem;
}