/* ============================================
   DESIGN SYSTEM — LIQUID GLASS (macOS 26)
   ============================================ */

:root,
[data-theme="light"] {
  --font-sans: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text",
               "Helvetica Neue", Helvetica, Arial, sans-serif;
  --font-mono: "SF Mono", SFMono-Regular, ui-monospace, Menlo, Monaco,
               "Cascadia Code", monospace;

  --bg-base: #f5f5f7;
  --bg-elevated: #ffffff;

  --glass-bg: rgba(255, 255, 255, 0.50);
  --glass-bg-hover: rgba(255, 255, 255, 0.72);
  --glass-bg-solid: rgba(255, 255, 255, 0.82);
  --glass-border: rgba(0, 0, 0, 0.06);
  --glass-shadow: 0 1px 3px rgba(0, 0, 0, 0.04),
                  0 8px 24px rgba(0, 0, 0, 0.06);
  --glass-shadow-hover: 0 2px 8px rgba(0, 0, 0, 0.06),
                        0 12px 32px rgba(0, 0, 0, 0.10);
  --glass-blur: 48px;
  --glass-saturate: 1.8;

  --text-primary: rgba(0, 0, 0, 0.88);
  --text-secondary: rgba(0, 0, 0, 0.50);
  --text-tertiary: rgba(0, 0, 0, 0.28);

  --accent: #007AFF;
  --accent-hover: #0066DD;
  --accent-soft: rgba(0, 122, 255, 0.08);

  --separator: rgba(0, 0, 0, 0.06);

  --radius-sm: 10px;
  --radius-md: 14px;
  --radius-lg: 20px;
  --radius-xl: 28px;
  --radius-pill: 980px;

  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-7: 32px;
  --space-8: 40px;
  --space-9: 48px;
  --space-10: 64px;
  --space-11: 80px;
  --space-12: 96px;

  --container: 960px;

  --transition-fast: 0.15s ease;
  --transition-normal: 0.3s ease;
  --transition-slow: 0.5s ease;

  --ambient-1: rgba(0, 122, 255, 0.05);
  --ambient-2: rgba(88, 86, 214, 0.04);
  --ambient-3: rgba(52, 199, 89, 0.03);

  color-scheme: light;
}

/* ============================================
   DARK MODE
   ============================================ */

[data-theme="dark"] {
  --bg-base: #000000;
  --bg-elevated: #1c1c1e;

  --glass-bg: rgba(44, 44, 46, 0.50);
  --glass-bg-hover: rgba(58, 58, 60, 0.60);
  --glass-bg-solid: rgba(44, 44, 46, 0.82);
  --glass-border: rgba(255, 255, 255, 0.07);
  --glass-shadow: 0 1px 3px rgba(0, 0, 0, 0.12),
                  0 8px 24px rgba(0, 0, 0, 0.20);
  --glass-shadow-hover: 0 2px 8px rgba(0, 0, 0, 0.16),
                        0 12px 32px rgba(0, 0, 0, 0.30);

  --text-primary: rgba(255, 255, 255, 0.88);
  --text-secondary: rgba(255, 255, 255, 0.55);
  --text-tertiary: rgba(255, 255, 255, 0.30);

  --accent: #0A84FF;
  --accent-hover: #409CFF;
  --accent-soft: rgba(10, 132, 255, 0.12);

  --separator: rgba(255, 255, 255, 0.07);

  --ambient-1: rgba(10, 132, 255, 0.06);
  --ambient-2: rgba(94, 92, 230, 0.05);
  --ambient-3: rgba(48, 209, 88, 0.03);

  color-scheme: dark;
}

/* ============================================
   RESET & BASE
   ============================================ */

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

html {
  scroll-behavior: smooth;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    transition-duration: 0.01ms !important;
  }
}

body {
  min-height: 100vh;
  background: var(--bg-base);
  color: var(--text-primary);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.47;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  transition: background var(--transition-normal), color var(--transition-normal);
}

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

a {
  color: inherit;
  text-decoration: none;
}

a:focus-visible,
button:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

button { font: inherit; border: none; background: none; cursor: pointer; }

.container {
  width: min(calc(100% - var(--space-7)), var(--container));
  margin: 0 auto;
}

/* ============================================
   AMBIENT BACKGROUND GLOW
   ============================================ */

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background: radial-gradient(ellipse 70% 60% at 50% 50%, transparent 30%, rgba(0, 0, 0, 0.25) 100%);
  pointer-events: none;
  z-index: -1;
  transition: background var(--transition-slow);
}

[data-theme="light"] body::before {
  background: radial-gradient(ellipse 70% 60% at 50% 50%, transparent 30%, rgba(0, 0, 0, 0.06) 100%);
}

/* ============================================
   GLASS UTILITY
   ============================================ */

.glass-panel {
  background: var(--glass-bg);
  backdrop-filter: blur(var(--glass-blur)) saturate(var(--glass-saturate));
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(var(--glass-saturate));
  border: 0.5px solid var(--glass-border);
  border-radius: var(--radius-xl);
  box-shadow: var(--glass-shadow);
  padding: var(--space-8);
  transition: background var(--transition-normal),
              box-shadow var(--transition-normal),
              border-color var(--transition-normal);
}

/* ============================================
   HEADER — Floating Glass Pill
   ============================================ */

.site-header {
  position: fixed;
  top: var(--space-4);
  left: 50%;
  transform: translateX(-50%);
  z-index: 100;
  width: min(calc(100% - var(--space-7)), 600px);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 48px;
  padding: 0 var(--space-5);
  background: var(--glass-bg-solid);
  backdrop-filter: blur(var(--glass-blur)) saturate(var(--glass-saturate));
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(var(--glass-saturate));
  border: 0.5px solid var(--glass-border);
  border-radius: var(--radius-pill);
  box-shadow: var(--glass-shadow);
  transition: background var(--transition-normal),
              border-color var(--transition-normal),
              box-shadow var(--transition-normal);
}

.brand {
  font-size: 15px;
  font-weight: 700;
  letter-spacing: 0.06em;
  color: var(--text-primary);
  transition: color var(--transition-fast);
}

.brand:hover { color: var(--accent); }

.nav-links {
  display: flex;
  gap: var(--space-6);
  font-size: 14px;
  font-weight: 500;
  color: var(--text-secondary);
}

.nav-links a {
  transition: color var(--transition-fast);
  padding: var(--space-1) 0;
}

.nav-links a:hover,
.nav-links a:focus-visible {
  color: var(--accent);
}

.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 32px;
  height: 32px;
  border-radius: 50%;
  color: var(--text-secondary);
  transition: color var(--transition-fast),
              background var(--transition-fast);
}

.theme-toggle:hover {
  color: var(--accent);
  background: var(--accent-soft);
}

[data-theme="light"] .icon-moon,
:root .icon-moon { display: none; }
[data-theme="light"] .icon-sun,
:root .icon-sun { display: block; }

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

/* ============================================
   HERO VIGNETTE
   ============================================ */

.hero-center {
  position: relative;
  z-index: 1;
}

/* ============================================
   HERO — Centered Layout
   ============================================ */

.hero {
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: var(--space-12) var(--space-7) var(--space-10);
  position: relative;
  overflow: hidden;
}

.hero-center {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  max-width: 640px;
}

.profile-image {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  object-fit: cover;
  object-position: center 18%;
  border: 3px solid var(--glass-border);
  box-shadow: 0 8px 40px rgba(0, 0, 0, 0.10);
  margin-bottom: var(--space-7);
  transition: border-color var(--transition-normal),
              box-shadow var(--transition-normal);
}

[data-theme="dark"] .profile-image {
  box-shadow: 0 8px 40px rgba(0, 0, 0, 0.30);
}

.hero .section-tag {
  margin-bottom: var(--space-2);
}

.hero h1 {
  margin-top: 0;
  font-size: clamp(2.8rem, 7vw, 4rem);
  font-weight: 700;
  line-height: 1.05;
  letter-spacing: -0.03em;
}

.hero-subtitle {
  margin-top: var(--space-4);
  color: var(--text-secondary);
  font-size: 17px;
  font-weight: 400;
  line-height: 1.5;
}

.hero-description {
  margin-top: var(--space-4);
  color: var(--text-secondary);
  font-size: 16px;
  line-height: 1.65;
  max-width: 520px;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: var(--space-3);
  margin-top: var(--space-7);
}

.hero-actions a {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-6);
  background: var(--glass-bg);
  backdrop-filter: blur(24px) saturate(1.6);
  -webkit-backdrop-filter: blur(24px) saturate(1.6);
  border: 0.5px solid var(--glass-border);
  border-radius: var(--radius-pill);
  color: var(--text-primary);
  font-size: 15px;
  font-weight: 500;
  box-shadow: var(--glass-shadow);
  transition: background var(--transition-normal),
              box-shadow var(--transition-normal),
              transform var(--transition-normal),
              color var(--transition-fast),
              border-color var(--transition-normal);
}

.hero-actions a:hover,
.hero-actions a:focus-visible {
  background: var(--glass-bg-hover);
  box-shadow: var(--glass-shadow-hover);
  transform: translateY(-2px);
  color: var(--accent);
}

/* ============================================
   TYPOGRAPHY
   ============================================ */

h1, h2, h3 {
  font-family: var(--font-sans);
  color: var(--text-primary);
  letter-spacing: -0.02em;
}

h1 {
  font-size: clamp(2rem, 5vw, 2.8rem);
  font-weight: 700;
  line-height: 1.1;
}

h2 {
  font-size: clamp(1.5rem, 3.5vw, 1.85rem);
  font-weight: 700;
  line-height: 1.2;
  margin-top: var(--space-3);
}

h3 { font-weight: 600; }

.section-tag {
  display: inline-block;
  color: var(--accent);
  font-size: 13px;
  font-weight: 600;
  letter-spacing: 0.03em;
  text-transform: uppercase;
}

/* ============================================
   SECTIONS
   ============================================ */

.section {
  padding: var(--space-10) 0;
}

.section-heading {
  margin-bottom: var(--space-7);
}

/* ============================================
   ABOUT
   ============================================ */

.about-grid {
  display: grid;
  grid-template-columns: 1.3fr 0.7fr;
  gap: var(--space-8);
  margin-top: var(--space-7);
}

.about-copy p {
  color: var(--text-secondary);
  font-size: 16px;
  line-height: 1.7;
}

.about-copy p + p {
  margin-top: var(--space-5);
}

.highlights {
  display: grid;
  gap: var(--space-3);
  align-content: start;
}

.highlight-card {
  padding: var(--space-4);
  background: rgba(44, 44, 46, 0.50);
  border-radius: var(--radius-md);
  transition: background var(--transition-normal),
              transform var(--transition-normal);
}

[data-theme="light"] .highlight-card {
  background: rgba(0, 0, 0, 0.04);
}

.highlight-card:hover {
  transform: translateY(-1px);
}

.highlight-card strong {
  display: block;
  margin-bottom: var(--space-1);
  font-size: 14px;
  font-weight: 600;
  color: var(--text-primary);
}

.highlight-card span {
  color: var(--text-secondary);
  font-size: 13px;
  line-height: 1.5;
}

/* ============================================
   ARTICLE CARDS
   ============================================ */

.articles-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-5);
}

.article-card {
  padding: var(--space-6);
  background: var(--glass-bg);
  backdrop-filter: blur(var(--glass-blur)) saturate(var(--glass-saturate));
  -webkit-backdrop-filter: blur(var(--glass-blur)) saturate(var(--glass-saturate));
  border: 0.5px solid var(--glass-border);
  border-radius: var(--radius-lg);
  box-shadow: var(--glass-shadow);
  display: flex;
  flex-direction: column;
  transition: background var(--transition-normal),
              box-shadow var(--transition-normal),
              transform var(--transition-normal),
              border-color var(--transition-normal);
}

a.article-card {
  cursor: pointer;
}

.article-card--featured {
  grid-column: 1 / -1;
  background: var(--glass-bg-solid);
  border-color: var(--accent);
  border-width: 1px;
  position: relative;
}

.article-card--featured h3 {
  font-size: 24px;
}

.article-featured-badge {
  display: inline-block;
  padding: var(--space-1) var(--space-3);
  margin-bottom: var(--space-3);
  background: var(--accent);
  color: #fff;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  border-radius: var(--radius-sm);
  width: fit-content;
}

.article-card:hover {
  background: var(--glass-bg-hover);
  box-shadow: var(--glass-shadow-hover);
  transform: translateY(-3px);
}

.article-category {
  display: inline-block;
  padding: var(--space-1) var(--space-3);
  margin-bottom: var(--space-3);
  background: var(--accent-soft);
  color: var(--accent);
  font-size: 11px;
  font-weight: 600;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border-radius: var(--radius-sm);
  width: fit-content;
}

.article-card h3 {
  font-size: 20px;
  line-height: 1.25;
}

.article-card p {
  margin-top: var(--space-3);
  color: var(--text-secondary);
  font-size: 15px;
  line-height: 1.6;
  flex: 1;
}

.article-meta-row {
  display: flex;
  gap: var(--space-4);
  margin-top: var(--space-4);
  margin-bottom: var(--space-4);
  color: var(--text-tertiary);
  font-size: 13px;
}

.article-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  color: var(--accent);
  font-size: 15px;
  font-weight: 600;
  transition: color var(--transition-fast), gap var(--transition-normal);
}

.article-link::after {
  content: "\2192";
  transition: transform var(--transition-normal);
}

.article-link:hover,
.article-link:focus-visible {
  color: var(--accent-hover);
}

.article-link:hover::after,
.article-link:focus-visible::after {
  transform: translateX(4px);
}

/* ============================================
   FOOTER
   ============================================ */

.site-footer {
  padding: var(--space-9) 0;
  text-align: center;
  color: var(--text-tertiary);
  font-size: 13px;
  border-top: 0.5px solid var(--separator);
}

/* ============================================
   ARTICLE PAGE
   ============================================ */

.article-page {
  max-width: 760px;
  padding-top: var(--space-12);
  padding-bottom: var(--space-10);
}

.back-link {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  margin-bottom: var(--space-7);
  color: var(--accent);
  font-size: 15px;
  font-weight: 500;
  transition: color var(--transition-fast), gap var(--transition-normal);
}

.back-link:hover,
.back-link:focus-visible {
  color: var(--accent-hover);
  gap: var(--space-3);
}

.back-link svg {
  flex-shrink: 0;
}

.article-panel {
  padding: var(--space-9) var(--space-8);
}

.article-header {
  padding-bottom: var(--space-7);
  border-bottom: 0.5px solid var(--separator);
}

.article-header .article-category {
  margin-bottom: var(--space-4);
}

.article-header h1 {
  font-size: clamp(1.8rem, 4.5vw, 2.4rem);
  line-height: 1.15;
  letter-spacing: -0.025em;
}

.article-meta {
  margin-top: var(--space-4);
  color: var(--text-tertiary);
  font-size: 14px;
}

.article-summary {
  margin-top: var(--space-4);
  color: var(--text-secondary);
  font-size: 17px;
  line-height: 1.7;
}

/* ============================================
   ARTICLE BODY
   ============================================ */

.article-body {
  padding-top: var(--space-8);
}

.article-body h2 {
  margin: var(--space-9) 0 var(--space-4);
  font-size: 22px;
  font-weight: 700;
}

.article-body p {
  color: var(--text-secondary);
  font-size: 17px;
  line-height: 1.75;
}

.article-body p + p {
  margin-top: var(--space-5);
}

.article-body ul {
  margin: var(--space-4) 0;
  padding-left: var(--space-6);
  color: var(--text-secondary);
  font-size: 17px;
  line-height: 1.75;
}

.article-body li + li {
  margin-top: var(--space-2);
}

.article-body li::marker {
  color: var(--accent);
}

.article-body pre {
  margin: var(--space-6) 0;
  padding: var(--space-5) var(--space-6);
  overflow-x: auto;
  background: var(--glass-bg);
  backdrop-filter: blur(24px) saturate(1.5);
  -webkit-backdrop-filter: blur(24px) saturate(1.5);
  border: 0.5px solid var(--glass-border);
  border-radius: var(--radius-md);
  box-shadow: var(--glass-shadow);
}

.article-body code {
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--text-primary);
  line-height: 1.6;
}

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

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

/* ============================================
   RESPONSIVE — Tablet (860px)
   ============================================ */

@media (max-width: 860px) {
  .about-grid {
    grid-template-columns: 1fr;
    gap: var(--space-7);
  }

  .glass-panel {
    padding: var(--space-7);
  }

  .article-panel {
    padding: var(--space-7) var(--space-6);
  }
}

/* ============================================
   RESPONSIVE — Mobile (640px)
   ============================================ */

@media (max-width: 640px) {
  .container {
    width: min(calc(100% - var(--space-5)), var(--container));
  }

  .site-header {
    width: min(calc(100% - var(--space-5)), 600px);
  }

  .header-inner {
    padding: 0 var(--space-4);
  }

  .nav-links {
    gap: var(--space-4);
    font-size: 13px;
  }

  .hero {
    min-height: auto;
    padding: calc(var(--space-12) + var(--space-8)) var(--space-4) var(--space-10);
  }

  .profile-image {
    width: 110px;
    height: 110px;
    margin-bottom: var(--space-6);
  }

  .hero h1 {
    font-size: clamp(2rem, 9vw, 2.8rem);
  }

  .section {
    padding: var(--space-9) 0;
  }

  .glass-panel {
    padding: var(--space-6);
    border-radius: var(--radius-lg);
  }

  .article-panel {
    padding: var(--space-6) var(--space-5);
    border-radius: var(--radius-lg);
  }

  .articles-grid {
    grid-template-columns: 1fr;
  }

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

  .article-page {
    padding-top: calc(var(--space-12) + var(--space-4));
  }

  .article-meta-row {
    flex-direction: column;
    gap: var(--space-1);
  }
}