/* ============================================
   Brian's Website — Apple-style Minimal CSS
   ============================================ */

:root {
  --bg: #ffffff;
  --bg-soft: #fbfbfd;
  --bg-muted: #f5f5f7;
  --text: #1d1d1f;
  --text-secondary: #6e6e73;
  --text-tertiary: #86868b;
  --border: #d2d2d7;
  --accent: #0071e3;
  --accent-hover: #0077ed;
  --radius: 18px;
  --radius-lg: 24px;
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.04);
  --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.06);
  --shadow-lg: 0 20px 40px rgba(0, 0, 0, 0.08);
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text",
    "Helvetica Neue", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
  --font-mono: "SF Mono", "JetBrains Mono", Menlo, Monaco, Consolas, monospace;
  --transition: 0.4s cubic-bezier(0.16, 1, 0.3, 1);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #000000;
    --bg-soft: #0a0a0a;
    --bg-muted: #1d1d1f;
    --text: #f5f5f7;
    --text-secondary: #a1a1a6;
    --text-tertiary: #6e6e73;
    --border: #2c2c2e;
    --accent: #2997ff;
    --accent-hover: #4dacff;
  }
}

* { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

body {
  margin: 0;
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  font-size: 17px;
  letter-spacing: -0.011em;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
  font-weight: 600;
  letter-spacing: -0.022em;
  line-height: 1.15;
  color: var(--text);
  margin: 0;
}

h1 { font-size: clamp(2.5rem, 5vw, 4.5rem); }
h2 { font-size: clamp(2rem, 3.5vw, 3rem); }
h3 { font-size: clamp(1.5rem, 2.2vw, 1.875rem); }
h4 { font-size: 1.25rem; }

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

/* Container */
.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
}

@media (min-width: 768px) {
  .container { padding: 0 40px; }
}

/* ===== Navbar ===== */
.nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid transparent;
  transition: border-color 0.3s, background 0.3s;
}

@media (prefers-color-scheme: dark) {
  .nav { background: rgba(0, 0, 0, 0.72); }
}

.nav.scrolled {
  border-bottom-color: var(--border);
}

.nav-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 24px;
  height: 56px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}

@media (min-width: 768px) {
  .nav-inner { padding: 0 40px; }
}

.nav-logo {
  font-weight: 600;
  font-size: 1.125rem;
  letter-spacing: -0.02em;
  color: var(--text);
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: 8px;
}

.nav-links {
  display: none;
  align-items: center;
  gap: 32px;
  list-style: none;
  margin: 0;
  padding: 0;
}

@media (min-width: 768px) {
  .nav-links { display: flex; }
}

.nav-link {
  color: var(--text);
  text-decoration: none;
  font-size: 0.875rem;
  font-weight: 400;
  opacity: 0.85;
  transition: opacity 0.2s;
  position: relative;
}

.nav-link:hover { opacity: 1; }

.nav-link.active::after {
  content: "";
  position: absolute;
  bottom: -4px;
  left: 0;
  right: 0;
  height: 1.5px;
  background: var(--text);
  border-radius: 2px;
}

.nav-toggle {
  display: flex;
  flex-direction: column;
  gap: 4px;
  background: none;
  border: none;
  cursor: pointer;
  padding: 8px;
}

@media (min-width: 768px) {
  .nav-toggle { display: none; }
}

.nav-toggle span {
  display: block;
  width: 18px;
  height: 1.5px;
  background: var(--text);
  border-radius: 1px;
  transition: transform 0.2s, opacity 0.2s;
}

.nav-mobile {
  display: none;
  flex-direction: column;
  padding: 16px 24px 24px;
  border-top: 1px solid var(--border);
  background: var(--bg-soft);
}

.nav-mobile.open { display: flex; }

.nav-mobile a {
  padding: 12px 0;
  color: var(--text);
  text-decoration: none;
  font-size: 1.125rem;
  border-bottom: 1px solid var(--border);
}

.nav-mobile a:last-child { border-bottom: none; }

/* ===== Hero ===== */
.hero {
  padding: 96px 0 80px;
  text-align: center;
}

.hero-eyebrow {
  font-size: 0.875rem;
  color: var(--text-tertiary);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 16px;
  font-weight: 500;
}

.hero-title {
  background: linear-gradient(180deg, var(--text) 0%, var(--text-secondary) 100%);
  -webkit-background-clip: text;
  background-clip: text;
  -webkit-text-fill-color: transparent;
  margin-bottom: 24px;
}

.hero-sub {
  font-size: clamp(1.125rem, 2vw, 1.375rem);
  color: var(--text-secondary);
  max-width: 680px;
  margin: 0 auto 40px;
  line-height: 1.5;
}

.hero-actions {
  display: flex;
  gap: 16px;
  justify-content: center;
  flex-wrap: wrap;
}

/* ===== Buttons ===== */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 12px 24px;
  border-radius: 980px;
  font-size: 0.9375rem;
  font-weight: 400;
  text-decoration: none;
  border: 1px solid transparent;
  cursor: pointer;
  transition: all 0.25s cubic-bezier(0.16, 1, 0.3, 1);
  line-height: 1.2;
}

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

.btn-primary:hover {
  background: var(--accent-hover);
  transform: translateY(-1px);
}

.btn-secondary {
  background: var(--bg-muted);
  color: var(--text);
  border-color: var(--border);
}

.btn-secondary:hover {
  background: var(--bg-soft);
  transform: translateY(-1px);
}

.btn-ghost {
  color: var(--accent);
  padding: 8px 0;
}

.btn-ghost::after {
  content: "→";
  transition: transform 0.2s;
}

.btn-ghost:hover::after {
  transform: translateX(4px);
}

/* ===== Section ===== */
.section {
  padding: 80px 0;
}

@media (min-width: 768px) {
  .section { padding: 120px 0; }
}

.section-header {
  text-align: center;
  margin-bottom: 64px;
}

.section-eyebrow {
  font-size: 0.875rem;
  color: var(--accent);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-weight: 500;
  margin-bottom: 12px;
}

.section-title { margin-bottom: 16px; }

.section-sub {
  font-size: 1.125rem;
  color: var(--text-secondary);
  max-width: 640px;
  margin: 0 auto;
}

/* ===== Grid ===== */
.grid {
  display: grid;
  gap: 24px;
}

.grid-2 { grid-template-columns: repeat(1, 1fr); }
.grid-3 { grid-template-columns: repeat(1, 1fr); }

@media (min-width: 768px) {
  .grid-2 { grid-template-columns: repeat(2, 1fr); }
  .grid-3 { grid-template-columns: repeat(2, 1fr); }
}

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

/* ===== Card ===== */
.card {
  background: var(--bg-soft);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  overflow: hidden;
  transition: all var(--transition);
  text-decoration: none;
  color: inherit;
  display: flex;
  flex-direction: column;
}

.card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
  border-color: transparent;
}

.card-image {
  width: 100%;
  aspect-ratio: 16 / 10;
  overflow: hidden;
  background: var(--bg-muted);
}

.card-image img {
  width: 100%;
  height: 100%;
  object-fit: cover;
  transition: transform 0.6s cubic-bezier(0.16, 1, 0.3, 1);
}

.card:hover .card-image img {
  transform: scale(1.04);
}

.card-body {
  padding: 24px 24px 28px;
  flex: 1;
  display: flex;
  flex-direction: column;
}

.card-tag {
  display: inline-block;
  font-size: 0.75rem;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.06em;
  font-weight: 500;
  margin-bottom: 8px;
}

.card-title {
  font-size: 1.25rem;
  font-weight: 600;
  margin-bottom: 8px;
  letter-spacing: -0.018em;
}

.card-excerpt {
  font-size: 0.9375rem;
  color: var(--text-secondary);
  margin: 0 0 16px;
  line-height: 1.5;
}

.card-meta {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 0.8125rem;
  color: var(--text-tertiary);
  margin-top: auto;
}

/* ===== Apple-style Project Showcase ===== */
.project-feature {
  margin-bottom: 120px;
}

.project-feature-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: 48px;
  align-items: center;
}

@media (min-width: 1024px) {
  .project-feature-grid { grid-template-columns: 1fr 1fr; gap: 80px; }
  .project-feature.reverse .project-feature-grid > :first-child {
    order: 2;
  }
}

.project-feature-cover {
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--bg-muted);
  aspect-ratio: 4 / 3;
  box-shadow: var(--shadow-md);
}

.project-feature-cover img {
  width: 100%;
  height: 100%;
  object-fit: cover;
}

.project-feature-tag {
  font-size: 0.875rem;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 500;
  margin-bottom: 12px;
}

.project-feature-title {
  font-size: clamp(2rem, 4vw, 3rem);
  margin-bottom: 16px;
  letter-spacing: -0.025em;
  line-height: 1.1;
}

.project-feature-tagline {
  font-size: 1.25rem;
  color: var(--text);
  margin-bottom: 16px;
  font-weight: 500;
}

.project-feature-desc {
  color: var(--text-secondary);
  margin-bottom: 32px;
  font-size: 1.0625rem;
  line-height: 1.6;
}

.project-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-bottom: 32px;
}

.project-tag {
  font-size: 0.75rem;
  padding: 4px 12px;
  background: var(--bg-muted);
  color: var(--text-secondary);
  border-radius: 980px;
  border: 1px solid var(--border);
}

/* ===== Filter Tabs (Blog) ===== */
.filter-tabs {
  display: flex;
  gap: 8px;
  overflow-x: auto;
  padding: 8px 0 16px;
  margin-bottom: 48px;
  scrollbar-width: none;
  -ms-overflow-style: none;
}

.filter-tabs::-webkit-scrollbar { display: none; }

.filter-tab {
  flex-shrink: 0;
  padding: 8px 18px;
  border-radius: 980px;
  background: var(--bg-muted);
  color: var(--text);
  border: 1px solid transparent;
  font-size: 0.875rem;
  font-weight: 500;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
}

.filter-tab:hover { background: var(--border); }

.filter-tab.active {
  background: var(--text);
  color: var(--bg);
}

/* ===== Post Detail ===== */
.post-hero {
  padding: 64px 0 32px;
  text-align: center;
}

.post-category {
  display: inline-block;
  font-size: 0.8125rem;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-weight: 500;
  margin-bottom: 16px;
}

.post-title {
  font-size: clamp(2rem, 4vw, 3.5rem);
  margin-bottom: 24px;
  max-width: 800px;
  margin-left: auto;
  margin-right: auto;
  letter-spacing: -0.025em;
  line-height: 1.1;
}

.post-meta {
  display: flex;
  justify-content: center;
  gap: 16px;
  align-items: center;
  color: var(--text-tertiary);
  font-size: 0.9375rem;
}

.post-cover {
  max-width: 960px;
  margin: 48px auto;
  border-radius: var(--radius-lg);
  overflow: hidden;
  background: var(--bg-muted);
}

.post-cover img {
  width: 100%;
  height: auto;
  display: block;
}

.post-content {
  max-width: 720px;
  margin: 0 auto;
  font-size: 1.0625rem;
  line-height: 1.8;
  color: var(--text);
}

.post-content h1, .post-content h2, .post-content h3 {
  margin-top: 2em;
  margin-bottom: 0.6em;
  letter-spacing: -0.02em;
}

.post-content h2 { font-size: 1.875rem; }
.post-content h3 { font-size: 1.5rem; }

.post-content p { margin: 1.2em 0; color: var(--text); }

.post-content a {
  color: var(--accent);
  text-decoration: none;
  border-bottom: 1px solid transparent;
  transition: border-color 0.2s;
}

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

.post-content img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius);
  margin: 2em 0;
  display: block;
  margin-left: auto;
  margin-right: auto;
}

.post-content blockquote {
  margin: 2em 0;
  padding: 4px 0 4px 20px;
  border-left: 3px solid var(--accent);
  color: var(--text-secondary);
  font-style: italic;
}

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

.post-content pre {
  background: #1d1d1f;
  color: #f5f5f7;
  padding: 20px 24px;
  border-radius: var(--radius);
  overflow-x: auto;
  font-size: 0.875rem;
  line-height: 1.6;
  margin: 2em 0;
}

.post-content pre code {
  background: none;
  padding: 0;
  color: inherit;
  font-size: inherit;
}

.post-content ul, .post-content ol {
  padding-left: 1.6em;
  margin: 1.2em 0;
}

.post-content li { margin: 0.5em 0; }

.post-content hr {
  border: none;
  border-top: 1px solid var(--border);
  margin: 3em auto;
  max-width: 200px;
}

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--border);
  padding: 48px 0 32px;
  margin-top: 80px;
}

.footer-inner {
  display: flex;
  flex-direction: column;
  gap: 16px;
  align-items: center;
  text-align: center;
}

@media (min-width: 768px) {
  .footer-inner {
    flex-direction: row;
    justify-content: space-between;
    text-align: left;
  }
}

.footer-text {
  color: var(--text-tertiary);
  font-size: 0.875rem;
  margin: 0;
}

.footer-links {
  display: flex;
  gap: 24px;
  list-style: none;
  margin: 0;
  padding: 0;
}

.footer-links a {
  color: var(--text-secondary);
  text-decoration: none;
  font-size: 0.875rem;
  transition: color 0.2s;
}

.footer-links a:hover { color: var(--text); }

/* ===== Reveal Animations ===== */
.reveal {
  opacity: 0;
  transform: translateY(24px);
  transition: opacity 0.8s cubic-bezier(0.16, 1, 0.3, 1),
              transform 0.8s cubic-bezier(0.16, 1, 0.3, 1);
}

.reveal.is-visible {
  opacity: 1;
  transform: translateY(0);
}

/* Stagger children */
.reveal-stagger > * {
  opacity: 0;
  transform: translateY(20px);
  transition: opacity 0.6s ease, transform 0.6s ease;
}

.reveal-stagger.is-visible > * {
  opacity: 1;
  transform: translateY(0);
}

.reveal-stagger.is-visible > *:nth-child(1) { transition-delay: 0ms; }
.reveal-stagger.is-visible > *:nth-child(2) { transition-delay: 80ms; }
.reveal-stagger.is-visible > *:nth-child(3) { transition-delay: 160ms; }
.reveal-stagger.is-visible > *:nth-child(4) { transition-delay: 240ms; }
.reveal-stagger.is-visible > *:nth-child(5) { transition-delay: 320ms; }
.reveal-stagger.is-visible > *:nth-child(6) { transition-delay: 400ms; }

/* ===== Empty / Loading ===== */
.empty {
  text-align: center;
  padding: 80px 24px;
  color: var(--text-tertiary);
}

.spinner {
  display: inline-block;
  width: 24px;
  height: 24px;
  border: 2px solid var(--border);
  border-top-color: var(--accent);
  border-radius: 50%;
  animation: spin 0.8s linear infinite;
}

@keyframes spin {
  to { transform: rotate(360deg); }
}

/* ===== Utility ===== */
.text-center { text-align: center; }
.mt-12 { margin-top: 48px; }
.mt-16 { margin-top: 64px; }
.mb-8 { margin-bottom: 32px; }
.hidden { display: none !important; }