/* ============================================================
   ai.feifei.tw — Design System CSS
   Apple Developer Docs × Anthropic Docs × Stripe × Linear
   Warm brown brand · Noto Sans TC · Systematic spacing
   ============================================================ */

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

/* ============ Design Tokens ============ */
:root {
  /* Color — Light */
  --color-bg: #FFFFFF;
  --color-surface: #F8F6F3;
  --color-surface-2: #F0EDE8;
  --color-border: #E5E0DA;
  --color-border-subtle: #EEEBE6;
  --color-text: #1A1A1A;
  --color-text-2: #555555;
  --color-text-3: #888888;
  --color-brand: #664F40;
  --color-brand-hover: #4F3C30;
  --color-accent: #005E61;
  --color-accent-hover: #004A4D;
  --color-accent-surface: #E8F4F4;
  --color-warning: #C4820A;
  --color-warning-surface: #FFF8EB;
  --color-danger: #B23A3A;
  --color-danger-surface: #FEF2F2;
  --color-success: #1A7A3A;
  --color-success-surface: #F0FDF4;

  /* Spacing — 4px base */
  --sp-1: 4px;
  --sp-2: 8px;
  --sp-3: 12px;
  --sp-4: 16px;
  --sp-6: 24px;
  --sp-8: 32px;
  --sp-10: 40px;
  --sp-12: 48px;
  --sp-16: 64px;
  --sp-20: 80px;
  --sp-24: 96px;

  /* Radius */
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 14px;
  --radius-xl: 20px;
  --radius-full: 9999px;

  /* Shadow */
  --shadow-sm: 0 1px 2px rgba(0,0,0,0.03), 0 1px 3px rgba(0,0,0,0.04);
  --shadow-md: 0 2px 8px rgba(0,0,0,0.04), 0 4px 16px rgba(0,0,0,0.06);
  --shadow-lg: 0 4px 12px rgba(0,0,0,0.04), 0 8px 32px rgba(0,0,0,0.08);
  --shadow-xl: 0 8px 24px rgba(0,0,0,0.06), 0 16px 48px rgba(0,0,0,0.10);

  /* Layout */
  --max-w: 1200px;
  --max-w-article: 720px;
  --max-w-narrow: 560px;

  /* Header */
  --header-h: 64px;
  --header-bg: rgba(255,255,255,0.92);
}

/* ============ Dark Mode ============ */
html[data-theme="dark"] {
  color-scheme: dark;
  --color-bg: #141210;
  --color-surface: #1E1B18;
  --color-surface-2: #282420;
  --color-border: #3A3530;
  --color-border-subtle: #2E2A26;
  --color-text: #E8E4E0;
  --color-text-2: #A8A098;
  --color-text-3: #706860;
  --color-brand: #D4B89A;
  --color-brand-hover: #E0C8AE;
  --color-accent: #4DB8BB;
  --color-accent-hover: #6DCED0;
  --color-accent-surface: #1A2E2E;
  --color-warning: #E0A030;
  --color-warning-surface: #2A2010;
  --color-danger: #E06060;
  --color-danger-surface: #2A1515;
  --color-success: #40B060;
  --color-success-surface: #152A18;
  --header-bg: rgba(20,18,16,0.92);
}

/* ============ Base ============ */
html {
  scroll-behavior: smooth;
  font-size: 16px;
  text-rendering: optimizeLegibility;
  -webkit-text-size-adjust: 100%;
}

body {
  font-family: "Noto Sans TC", system-ui, -apple-system, sans-serif;
  font-size: 1.0625rem;
  font-weight: 400;
  line-height: 1.7;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
}

a { color: var(--color-accent); text-decoration: none; transition: color 0.15s; }
a:hover { text-decoration: underline; color: var(--color-accent-hover); }
img { max-width: 100%; height: auto; display: block; }
::selection { background: var(--color-brand); color: #fff; }

/* ============ Focus ============ */
:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
  border-radius: var(--radius-sm);
}
:focus:not(:focus-visible) { outline: none; }

.skip-link {
  position: absolute; left: -9999px; top: auto;
  background: var(--color-brand); color: #fff;
  padding: var(--sp-2) var(--sp-4);
  border-radius: var(--radius-md);
  font-size: 0.875rem; font-weight: 600;
  z-index: 999;
}
.skip-link:focus { left: var(--sp-3); top: var(--sp-3); }

/* ============ Layout ============ */
.container { width: 100%; max-width: var(--max-w); margin: 0 auto; padding: 0 var(--sp-6); }
.container-article { max-width: var(--max-w-article); }
.container-narrow { max-width: var(--max-w-narrow); }

/* ============ Header ============ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--header-bg);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--color-border-subtle);
}

.header-inner {
  max-width: var(--max-w);
  margin: 0 auto;
  padding: 0 var(--sp-6);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--header-h);
}

.logo {
  font-weight: 900;
  font-size: 1.05rem;
  color: var(--color-brand);
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  text-decoration: none;
  white-space: nowrap;
  letter-spacing: -0.01em;
}
.logo:hover { text-decoration: none; color: var(--color-brand); }
.logo .dot,
.logo-dot {
  width: 10px; height: 10px;
  border-radius: 50%;
  background: var(--color-accent);
  display: inline-block;
}

.main-nav { display: flex; gap: var(--sp-6); align-items: center; }
.nav-link {
  color: var(--color-text-2);
  font-size: 0.9375rem;
  font-weight: 500;
  padding: var(--sp-1) 0;
  transition: color 0.15s;
  text-decoration: none;
}
.nav-link:hover { color: var(--color-text); text-decoration: none; }
.nav-link[aria-current="page"] { color: var(--color-text); font-weight: 600; }

.nav-cta {
  background: var(--color-brand);
  color: #fff !important;
  padding: var(--sp-2) var(--sp-4);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 600;
  white-space: nowrap;
  transition: background 0.15s;
  text-decoration: none;
}
.nav-cta:hover { background: var(--color-brand-hover); text-decoration: none; }

/* Header actions group */
.header-actions {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
}
.btn-icon {
  background: none;
  border: 1.5px solid var(--color-border);
  border-radius: 50%;
  width: 36px; height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--color-text-3);
  transition: border-color 0.15s, color 0.15s;
}
.btn-icon:hover { border-color: var(--color-brand); color: var(--color-brand); }

/* Theme toggle */
.theme-toggle {
  background: none;
  border: 1.5px solid var(--color-border);
  border-radius: 50%;
  width: 36px; height: 36px;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  color: var(--color-text-3);
  transition: border-color 0.15s, color 0.15s;
}
.theme-toggle:hover { border-color: var(--color-brand); color: var(--color-brand); }
html:not([data-theme="dark"]) .icon-moon { display: none; }
html[data-theme="dark"] .icon-sun { display: none; }

/* Mobile nav toggle */
.nav-toggle {
  display: none;
  background: none;
  border: none;
  cursor: pointer;
  width: 28px; height: 22px;
  flex-direction: column;
  justify-content: space-between;
  padding: 0;
}
.nav-toggle span {
  display: block;
  width: 100%;
  height: 2.5px;
  background: var(--color-brand);
  border-radius: 2px;
  transition: transform 0.25s ease, opacity 0.25s ease;
}

/* ============ Buttons ============ */
.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--sp-2);
  padding: var(--sp-3) var(--sp-6);
  border-radius: var(--radius-md);
  font-weight: 600;
  font-size: 0.9375rem;
  cursor: pointer;
  border: none;
  font-family: inherit;
  line-height: 1.4;
  transition: all 0.15s ease;
  text-align: center;
  text-decoration: none;
  white-space: nowrap;
}
.btn:hover { text-decoration: none; transform: translateY(-1px); }
.btn:active { transform: translateY(0); }

.btn-primary { background: var(--color-brand); color: #fff; box-shadow: 0 2px 8px rgba(102,79,64,0.25); }
.btn-primary:hover { background: var(--color-brand-hover); box-shadow: 0 4px 16px rgba(102,79,64,0.3); }

.btn-secondary { background: var(--color-surface); color: var(--color-brand); }
.btn-secondary:hover { background: var(--color-surface-2); }

.btn-ghost { background: transparent; color: var(--color-brand); border: 1.5px solid var(--color-border); }
.btn-ghost:hover { border-color: var(--color-brand); background: var(--color-surface); }

/* Legacy compat */
.btn-outline { background: transparent; color: var(--color-brand); border: 1.5px solid var(--color-brand); }
.btn-outline:hover { background: var(--color-brand); color: #fff; }

.btn-line { background: var(--color-brand); color: #fff; }
.btn-line:hover { background: var(--color-brand-hover); }

.btn-sm { padding: var(--sp-2) var(--sp-4); font-size: 0.875rem; }
.btn-lg { padding: var(--sp-4) var(--sp-8); font-size: 1rem; }

/* ============ Search ============ */
.search-input {
  display: flex;
  align-items: center;
  gap: var(--sp-2);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  padding: var(--sp-2) var(--sp-4);
  width: 100%;
  max-width: 480px;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.search-input:focus-within {
  border-color: var(--color-accent);
  box-shadow: 0 0 0 3px var(--color-accent-surface);
}
.search-input input {
  border: none;
  background: transparent;
  font-family: inherit;
  font-size: 0.9375rem;
  color: var(--color-text);
  width: 100%;
  outline: none;
}
.search-input input::placeholder { color: var(--color-text-3); }
.search-input svg { flex-shrink: 0; color: var(--color-text-3); }

/* ============ Filter Tabs ============ */
.filter-tabs {
  display: flex;
  gap: var(--sp-2);
  flex-wrap: wrap;
  margin-bottom: var(--sp-8);
}
.filter-tab {
  padding: var(--sp-2) var(--sp-4);
  border-radius: var(--radius-full);
  font-size: 0.875rem;
  font-weight: 500;
  color: var(--color-text-2);
  background: transparent;
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: all 0.15s;
  font-family: inherit;
  text-decoration: none;
}
.filter-tab:hover { border-color: var(--color-brand); color: var(--color-brand); text-decoration: none; }
.filter-tab.active,
.filter-tab[aria-selected="true"] {
  background: var(--color-brand);
  color: #fff;
  border-color: var(--color-brand);
}

/* ============ Hero ============ */
.hero {
  padding: var(--sp-24) 0 var(--sp-20);
  text-align: center;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border-subtle);
}
.hero .eyebrow,
.hero-eyebrow {
  display: inline-block;
  background: var(--color-accent-surface);
  color: var(--color-accent);
  font-weight: 600;
  font-size: 0.75rem;
  padding: var(--sp-1) var(--sp-4);
  border-radius: var(--radius-full);
  margin-bottom: var(--sp-8);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.hero h1,
.hero-title {
  font-size: clamp(2.5rem, 6vw, 3.5rem);
  font-weight: 900;
  color: var(--color-brand);
  letter-spacing: -0.03em;
  line-height: 1.1;
  margin-bottom: var(--sp-6);
}
.hero .subtitle {
  font-size: clamp(1.05rem, 2.5vw, 1.25rem);
  color: var(--color-text);
  font-weight: 500;
  max-width: 640px;
  margin: 0 auto var(--sp-4);
  line-height: 1.6;
}
.hero .desc,
.hero-desc {
  font-size: 1rem;
  color: var(--color-text-2);
  max-width: 520px;
  margin: 0 auto var(--sp-10);
  line-height: 1.7;
}
.hero .desc .hl {
  color: var(--color-text);
  font-weight: 600;
}
.hero-actions {
  display: flex;
  gap: var(--sp-3);
  justify-content: center;
  flex-wrap: wrap;
}

/* ============ Sections ============ */
section { padding: var(--sp-20) 0; }
.section { padding: var(--sp-20) 0; }
.section-alt { background: var(--color-surface); }
.section-cta { background: var(--color-surface); text-align: center; }

/* Breadcrumb (standalone) */
.breadcrumb {
  font-size: 0.8125rem;
  color: var(--color-text-3);
  margin-bottom: var(--sp-4);
  font-weight: 500;
}
.breadcrumb a { color: var(--color-accent); }
.breadcrumb .sep { color: var(--color-text-3); margin: 0 var(--sp-1); }

.section-subtitle {
  color: var(--color-text-3);
  font-size: 0.9375rem;
  margin-top: var(--sp-2);
}

.section-header {
  text-align: center;
  margin-bottom: var(--sp-12);
}
.section-title {
  text-align: center;
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  font-weight: 800;
  color: var(--color-text);
  margin-bottom: var(--sp-3);
  letter-spacing: -0.02em;
  line-height: 1.25;
}
.section-desc,
.section-sub {
  text-align: center;
  color: var(--color-text-3);
  margin-bottom: 0;
  font-size: 0.9375rem;
  line-height: 1.6;
}
.section-link {
  color: var(--color-accent);
  font-weight: 600;
  font-size: 0.9375rem;
  text-decoration: none;
}
.section-link:hover { text-decoration: underline; }

/* CTA section */
.cta-title {
  font-size: clamp(1.75rem, 4vw, 2.25rem);
  font-weight: 800;
  color: var(--color-text);
  margin-bottom: var(--sp-4);
  letter-spacing: -0.02em;
}
.cta-desc {
  color: var(--color-text-2);
  font-size: 0.9375rem;
  line-height: 1.7;
  max-width: 480px;
  margin: 0 auto var(--sp-10);
}

/* ============ Intent Grid ============ */
.intent-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-4);
}
.intent-grid > :nth-child(4),
.intent-grid > :nth-child(5) {
  grid-column: span 1;
}
@media (min-width: 1025px) {
  .intent-grid {
    grid-template-columns: repeat(5, 1fr);
  }
  .intent-grid > :nth-child(4),
  .intent-grid > :nth-child(5) {
    grid-column: span 1;
  }
}

.intent-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--sp-8) var(--sp-6);
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
  text-decoration: none;
  color: inherit;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s;
  box-shadow: var(--shadow-sm);
}
.intent-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border);
  text-decoration: none;
  color: inherit;
}
.intent-icon {
  width: 48px; height: 48px;
  border-radius: var(--radius-md);
  background: var(--color-accent-surface);
  color: var(--color-accent);
  display: flex;
  align-items: center;
  justify-content: center;
}
.intent-title {
  font-weight: 700;
  font-size: 1rem;
  color: var(--color-text);
  line-height: 1.4;
  margin: 0;
}
.intent-desc {
  font-size: 0.875rem;
  color: var(--color-text-2);
  line-height: 1.5;
  margin: 0;
}

/* ============ Tool Grid ============ */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  gap: var(--sp-4);
}
.tool-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--sp-8) var(--sp-4);
  text-align: center;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: var(--sp-2);
  text-decoration: none;
  color: inherit;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s;
  box-shadow: var(--shadow-sm);
}
.tool-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border);
  text-decoration: none;
  color: inherit;
}
.tool-name {
  font-weight: 800;
  font-size: 1.0625rem;
  color: var(--color-text);
  letter-spacing: -0.01em;
}
.tool-maker {
  font-size: 0.8125rem;
  color: var(--color-text-3);
  font-weight: 500;
}
.tool-risk {
  font-size: 0.6875rem;
  color: var(--color-text-3);
  margin-top: var(--sp-2);
  line-height: 1.4;
  padding: var(--sp-1) var(--sp-3);
  background: var(--color-surface);
  border-radius: var(--radius-full);
}

/* ============ Author Section ============ */
.author-section { text-align: center; }
.author-card {
  max-width: 600px;
  margin: 0 auto;
  padding: var(--sp-8) var(--sp-6);
}
.author-avatar {
  width: 80px; height: 80px;
  border-radius: 50%;
  background: var(--color-brand);
  color: #fff;
  font-size: 2rem;
  font-weight: 800;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 0 auto var(--sp-4);
}
.author-name {
  font-size: 1.5rem;
  font-weight: 800;
  color: var(--color-text);
  margin-bottom: var(--sp-1);
}
.author-title {
  font-size: 0.9375rem;
  color: var(--color-text-2);
  margin-bottom: var(--sp-4);
}
.author-bio {
  font-size: 0.9375rem;
  color: var(--color-text-2);
  line-height: 1.7;
  margin-bottom: var(--sp-6);
  max-width: 520px;
  margin-left: auto;
  margin-right: auto;
}
.author-badges {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-2);
  justify-content: center;
  margin-bottom: var(--sp-4);
}
.author-badge {
  background: var(--color-accent-surface);
  color: var(--color-accent);
  font-size: 0.8125rem;
  font-weight: 600;
  padding: var(--sp-1) var(--sp-3);
  border-radius: var(--radius-sm);
}

/* ============ Differentiator Grid ============ */
.diff-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-6);
}
.diff-card {
  text-align: center;
  padding: var(--sp-10) var(--sp-6);
  background: var(--color-bg);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-xl);
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}
.diff-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}
.diff-icon {
  width: 56px; height: 56px;
  border-radius: var(--radius-lg);
  background: var(--color-accent-surface);
  color: var(--color-accent);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-bottom: var(--sp-6);
}
.diff-card h3 {
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--color-text);
  margin-bottom: var(--sp-3);
}
.diff-card p {
  color: var(--color-text-2);
  font-size: 0.875rem;
  line-height: 1.7;
}

/* ============ Feature Cards ============ */
.features { background: var(--color-bg); }
.feature-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-6);
}
.feature-card {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  padding: var(--sp-8) var(--sp-6);
  text-align: center;
  border: 1px solid var(--color-border-subtle);
  transition: border-color 0.15s, box-shadow 0.15s;
}
.feature-card:hover { border-color: var(--color-border); box-shadow: var(--shadow-md); }
.feature-card .icon {
  font-size: 2rem;
  margin-bottom: var(--sp-4);
  display: inline-flex;
  width: 56px; height: 56px;
  align-items: center; justify-content: center;
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  color: var(--color-brand);
  border: 1px solid var(--color-border-subtle);
}
.feature-card h3 {
  font-weight: 700;
  font-size: 1.125rem;
  color: var(--color-brand);
  margin-bottom: var(--sp-2);
  letter-spacing: -0.01em;
}
.feature-card p { color: var(--color-text-2); font-size: 0.9375rem; line-height: 1.6; }

/* ============ Topic Grid (Knowledge Tree / Categories) ============ */
.topics { background: var(--color-bg); }
.topic-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: var(--sp-3);
}
.topic-card {
  background: var(--color-bg);
  border-radius: var(--radius-lg);
  padding: var(--sp-4) var(--sp-6);
  display: flex;
  align-items: center;
  gap: var(--sp-4);
  border: 1px solid var(--color-border-subtle);
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s;
  text-decoration: none;
  color: inherit;
}
.topic-card:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
  border-color: var(--color-border);
  text-decoration: none;
  color: inherit;
}
.topic-num {
  flex-shrink: 0;
  width: 40px; height: 40px;
  border-radius: var(--radius-md);
  background: var(--color-brand);
  color: #fff;
  font-weight: 800;
  font-size: 0.875rem;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
}
.topic-name {
  font-weight: 600;
  font-size: 0.9375rem;
  color: var(--color-text);
  line-height: 1.4;
}
.topic-card-lab {
  background: var(--color-surface);
  border-color: var(--color-warning);
}
.topic-card-lab .topic-num {
  background: var(--color-warning);
  color: #fff;
}

/* ============ Card (Blog listing — .card class) ============ */
.card {
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
  background: var(--color-bg);
  border-radius: var(--radius-xl);
  padding: var(--sp-6);
  border: 1px solid var(--color-border-subtle);
  text-decoration: none;
  color: inherit;
  box-shadow: var(--shadow-sm);
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s;
}
.card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border);
  text-decoration: none;
  color: inherit;
}
.card-category {
  display: inline-block;
  width: fit-content;
  background: var(--color-accent-surface);
  color: var(--color-accent);
  font-weight: 600;
  font-size: 0.8125rem;
  padding: var(--sp-1) var(--sp-3);
  border-radius: var(--radius-sm);
  letter-spacing: 0.01em;
}
.card-title {
  font-weight: 700;
  font-size: 1.0625rem;
  color: var(--color-text);
  line-height: 1.5;
  letter-spacing: -0.01em;
  margin: 0;
}
.card-desc {
  font-size: 0.9375rem;
  color: var(--color-text-2);
  line-height: 1.6;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}

/* ============ Article Card (Homepage featured) ============ */
.articles { background: var(--color-surface); }
.article-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--sp-6);
}
.article-card {
  background: var(--color-bg);
  border-radius: var(--radius-xl);
  border: 1px solid var(--color-border-subtle);
  box-shadow: var(--shadow-sm);
  display: flex;
  flex-direction: column;
  gap: var(--sp-3);
  padding: var(--sp-8) var(--sp-6);
  cursor: pointer;
  transition: transform 0.2s ease, box-shadow 0.2s ease, border-color 0.2s;
  text-decoration: none;
  color: inherit;
  overflow: hidden;
}
.article-card:hover {
  transform: translateY(-3px);
  box-shadow: var(--shadow-lg);
  border-color: var(--color-border);
  text-decoration: none;
  color: inherit;
}
.article-card-body { display: flex; flex-direction: column; gap: var(--sp-2); }
.article-card-cat {
  display: inline-block;
  width: fit-content;
  background: var(--color-accent-surface);
  color: var(--color-accent);
  font-weight: 600;
  font-size: 0.75rem;
  padding: var(--sp-1) var(--sp-3);
  border-radius: var(--radius-full);
  letter-spacing: 0.02em;
}
.article-card-title {
  font-weight: 700;
  font-size: 1.0625rem;
  color: var(--color-text);
  line-height: 1.45;
  letter-spacing: -0.01em;
}
.article-card-desc {
  font-size: 0.875rem;
  color: var(--color-text-3);
  line-height: 1.6;
  display: -webkit-box;
  -webkit-line-clamp: 2;
  -webkit-box-orient: vertical;
  overflow: hidden;
}
.article-card-date {
  font-size: 0.8125rem;
  color: var(--color-text-3);
  margin-top: auto;
}
.article-card-img {
  width: 100%;
  aspect-ratio: 1200/630;
  object-fit: cover;
}

/* Legacy card classes */
.article-card .card-meta { display: flex; align-items: center; gap: var(--sp-2); font-size: 0.8125rem; color: var(--color-text-3); }
.article-card .card-category { display: inline-block; background: var(--color-accent-surface); color: var(--color-accent); font-weight: 600; font-size: 0.8125rem; padding: var(--sp-1) var(--sp-3); border-radius: var(--radius-sm); }
.article-card .card-title { font-weight: 700; font-size: 1.0625rem; color: var(--color-text); line-height: 1.5; }
.article-card .card-excerpt { font-size: 0.9375rem; color: var(--color-text-2); line-height: 1.6; display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow: hidden; }
.article-card .card-tags { display: flex; flex-wrap: wrap; gap: var(--sp-1); margin-top: auto; }
.article-card .tag { font-size: 0.75rem; color: var(--color-text-3); background: var(--color-surface); padding: 2px var(--sp-2); border-radius: var(--radius-sm); }

/* ============ Article Page ============ */
.article-header {
  padding: var(--sp-16) 0 var(--sp-10);
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border-subtle);
}
.article-header .container { max-width: var(--max-w-article); }
.article-header .breadcrumb {
  font-size: 0.8125rem;
  color: var(--color-text-3);
  margin-bottom: var(--sp-6);
  font-weight: 500;
}
.article-header .breadcrumb a { color: var(--color-accent); }
.article-header .breadcrumb .sep { color: var(--color-text-3); margin: 0 var(--sp-1); }
.article-header h1 {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  font-weight: 800;
  color: var(--color-text);
  line-height: 1.2;
  letter-spacing: -0.025em;
  margin-bottom: var(--sp-6);
}
.article-header .article-meta {
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  font-size: 0.8125rem;
  color: var(--color-text-3);
  flex-wrap: wrap;
  font-weight: 500;
}
.article-header .article-category {
  display: inline-block;
  background: var(--color-accent-surface);
  color: var(--color-accent);
  font-weight: 600;
  font-size: 0.8125rem;
  padding: var(--sp-1) var(--sp-3);
  border-radius: var(--radius-sm);
}

/* Article with TOC layout */
.article-layout {
  width: 100%;
}

/* TOC Sidebar */
.toc-sidebar {
  position: sticky;
  top: calc(var(--header-h) + var(--sp-8));
  padding-top: var(--sp-10);
}
.toc-sidebar nav { border-left: 1px solid var(--color-border-subtle); padding-left: var(--sp-4); }
.toc-title {
  font-size: 0.8125rem;
  font-weight: 600;
  color: var(--color-text-3);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--sp-3);
}
.toc-link {
  display: block;
  font-size: 0.8125rem;
  color: var(--color-text-3);
  padding: var(--sp-1) 0;
  line-height: 1.5;
  transition: color 0.15s;
  text-decoration: none;
}
.toc-link:hover { color: var(--color-text); text-decoration: none; }
.toc-link.active { color: var(--color-accent); font-weight: 600; }

/* TOC (inline, article template) */
.toc {
  background: var(--color-surface);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--sp-8);
  margin-bottom: var(--sp-10);
}
.toc .toc-title {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-text);
  text-transform: none;
  letter-spacing: 0;
  margin-bottom: var(--sp-4);
}
.toc-list {
  list-style: decimal;
  padding-left: var(--sp-6);
  margin: 0;
}
.toc-list li { margin-bottom: var(--sp-2); }
.toc-list a {
  color: var(--color-accent);
  font-size: 0.9375rem;
  text-decoration: none;
  font-weight: 500;
}
.toc-list a:hover { text-decoration: underline; }

/* Related card (article template) */
.related-card {
  display: block;
  background: var(--color-surface);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--sp-4) var(--sp-6);
  text-decoration: none;
  transition: border-color 0.15s, box-shadow 0.15s;
}
.related-card:hover { border-color: var(--color-border); box-shadow: var(--shadow-sm); text-decoration: none; }
.related-title { font-weight: 600; color: var(--color-text); font-size: 0.9375rem; }

/* Article body */
.article-body {
  padding: var(--sp-10) 0 var(--sp-20);
}
.article-body .container { max-width: var(--max-w-article); }

.article-content {
  font-size: 1.0625rem;
  line-height: 1.7;
  color: var(--color-text);
}
.article-content h2 {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text);
  margin: var(--sp-12) 0 var(--sp-4);
  letter-spacing: -0.01em;
  line-height: 1.35;
  padding-bottom: var(--sp-2);
  border-bottom: 1px solid var(--color-border-subtle);
}
.article-content h3 {
  font-size: 1.2rem;
  font-weight: 600;
  color: var(--color-text);
  margin: var(--sp-8) 0 var(--sp-3);
  line-height: 1.4;
}
.article-content p { margin-bottom: var(--sp-4); }
.article-content ul, .article-content ol {
  margin: var(--sp-2) 0 var(--sp-4) var(--sp-6);
}
.article-content li { margin-bottom: var(--sp-2); }
.article-content li strong { color: var(--color-text); }

.article-content blockquote {
  background: var(--color-surface);
  border-left: 3px solid var(--color-brand);
  border-radius: 0 var(--radius-md) var(--radius-md) 0;
  padding: var(--sp-4) var(--sp-6);
  margin: var(--sp-6) 0;
  color: var(--color-text-2);
}

.article-content code {
  background: var(--color-surface-2);
  padding: 2px var(--sp-2);
  border-radius: var(--radius-sm);
  font-size: 0.9em;
  font-family: "SF Mono", "Fira Code", "Consolas", monospace;
}
.article-content pre {
  background: var(--color-surface);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--sp-6);
  overflow-x: auto;
  margin: var(--sp-4) 0;
}
.article-content pre code { background: none; padding: 0; font-size: 0.875rem; }

.article-content img {
  border-radius: var(--radius-lg);
  margin: var(--sp-6) 0;
}

.article-content a { color: var(--color-accent); font-weight: 500; }
.article-content a:hover { color: var(--color-accent-hover); }

/* Callouts */
.article-content .callout {
  background: var(--color-surface);
  border-radius: var(--radius-xl);
  padding: var(--sp-6) var(--sp-8);
  border-left: 4px solid var(--color-warning);
  margin: var(--sp-8) 0;
}
.article-content .callout-info {
  border-left-color: var(--color-accent);
  background: var(--color-accent-surface);
}
.article-content .callout-warning {
  border-left-color: var(--color-warning);
  background: var(--color-warning-surface);
}
.article-content .callout-danger {
  border-left-color: var(--color-danger);
  background: var(--color-danger-surface);
}
.article-content .callout-title {
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-2);
  font-size: 0.9375rem;
}

/* Article tags */
.article-tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--sp-2);
  margin-top: var(--sp-10);
  padding-top: var(--sp-6);
  border-top: 1px solid var(--color-border-subtle);
}
.article-tags .tag-label { font-size: 0.8125rem; color: var(--color-text-3); font-weight: 600; }
.article-tags .tag {
  font-size: 0.8125rem;
  color: var(--color-accent);
  background: var(--color-accent-surface);
  padding: var(--sp-1) var(--sp-3);
  border-radius: var(--radius-sm);
  font-weight: 500;
  text-decoration: none;
}
.article-tags .tag:hover { background: var(--color-surface-2); text-decoration: none; }

/* Article nav (prev/next) */
.article-nav {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--sp-4);
  margin-top: var(--sp-10);
  padding-top: var(--sp-6);
  border-top: 1px solid var(--color-border-subtle);
}
.article-nav a {
  background: var(--color-surface);
  color: var(--color-text);
  padding: var(--sp-4) var(--sp-6);
  border-radius: var(--radius-lg);
  font-size: 0.9375rem;
  border: 1px solid var(--color-border-subtle);
  transition: border-color 0.15s, box-shadow 0.15s;
  text-decoration: none;
  display: flex;
  flex-direction: column;
  gap: var(--sp-1);
}
.article-nav a:hover { border-color: var(--color-border); box-shadow: var(--shadow-sm); text-decoration: none; }
.article-nav-label { font-size: 0.8125rem; color: var(--color-text-3); font-weight: 500; }
.article-nav-title { font-weight: 600; color: var(--color-text); }
.article-nav-next { text-align: right; margin-left: auto; }

/* Related articles */
.related-articles {
  margin-top: var(--sp-16);
  padding-top: var(--sp-8);
  border-top: 1px solid var(--color-border-subtle);
}
.related-articles h2 {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-6);
}
.related-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: var(--sp-4);
}

/* ============ FAQ Accordion ============ */
.article-content details {
  background: var(--color-surface);
  border-radius: var(--radius-lg);
  margin-bottom: var(--sp-3);
  border: 1px solid var(--color-border-subtle);
  transition: border-color 0.15s;
}
.article-content details[open] { border-color: var(--color-border); }
.article-content details summary {
  padding: var(--sp-4) var(--sp-6);
  cursor: pointer;
  font-size: 1rem;
  font-weight: 600;
  line-height: 1.5;
  list-style: none;
  display: flex;
  align-items: center;
  gap: var(--sp-3);
  color: var(--color-text);
}
.article-content details summary::before {
  content: "+";
  flex-shrink: 0;
  width: 24px; height: 24px;
  border-radius: var(--radius-sm);
  background: var(--color-surface-2);
  color: var(--color-text-2);
  font-weight: 700;
  font-size: 1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  line-height: 1;
  transition: background 0.15s;
}
.article-content details[open] summary::before { content: "−"; background: var(--color-accent-surface); color: var(--color-accent); }
.article-content details summary::-webkit-details-marker { display: none; }
.article-content details > p,
.article-content details > div {
  padding: 0 var(--sp-6) var(--sp-4);
  padding-left: calc(var(--sp-6) + 24px + var(--sp-3));
  color: var(--color-text-2);
  font-size: 0.9375rem;
  line-height: 1.7;
}

/* ============ Tables ============ */
.table-wrapper {
  overflow-x: auto;
  margin: var(--sp-4) 0;
  border-radius: var(--radius-lg);
  border: 1px solid var(--color-border-subtle);
  position: relative;
}
/* Scroll hint — gradient fade on right */
.table-wrapper::after {
  content: "";
  position: absolute;
  top: 0; right: 0; bottom: 0;
  width: 40px;
  background: linear-gradient(to right, transparent, var(--color-bg));
  pointer-events: none;
  opacity: 0;
  transition: opacity 0.2s;
}
.table-wrapper.is-scrollable::after { opacity: 1; }

.article-content table {
  width: 100%;
  border-collapse: collapse;
  background: var(--color-bg);
  margin: var(--sp-4) 0;
}
.article-content th {
  background: var(--color-surface);
  color: var(--color-text);
  text-align: left;
  padding: var(--sp-3) var(--sp-4);
  font-size: 0.8125rem;
  font-weight: 700;
  letter-spacing: 0.01em;
  text-transform: uppercase;
  border-bottom: 1px solid var(--color-border);
  white-space: nowrap;
}
.article-content td {
  padding: var(--sp-3) var(--sp-4);
  border-bottom: 1px solid var(--color-border-subtle);
  font-size: 0.9375rem;
}
.article-content td:first-child { font-weight: 600; color: var(--color-text); }
.article-content tr:last-child td { border-bottom: none; }

/* ============ Security Rating ============ */
.security-rating {
  background: var(--color-surface);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-xl);
  padding: var(--sp-8);
  margin: var(--sp-8) 0;
}
.security-rating h3 {
  font-size: 1rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-4);
}
.security-rating-title {
  font-size: 0.9375rem;
  font-weight: 700;
  color: var(--color-text);
  margin-bottom: var(--sp-4);
  display: flex;
  align-items: center;
  gap: var(--sp-2);
}
.security-rating-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--sp-3);
}
.security-rating-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--sp-2) var(--sp-3);
  background: var(--color-bg);
  border-radius: var(--radius-md);
  font-size: 0.875rem;
}
.security-rating-label { color: var(--color-text-2); font-weight: 500; }
.security-rating-value {
  font-weight: 700;
  font-size: 0.8125rem;
  padding: 2px var(--sp-2);
  border-radius: var(--radius-sm);
}
.security-rating-value.low { background: var(--color-success-surface); color: var(--color-success); }
.security-rating-value.medium { background: var(--color-warning-surface); color: var(--color-warning); }
.security-rating-value.high { background: var(--color-danger-surface); color: var(--color-danger); }

/* Rating table (article template) */
.rating-table {
  width: 100%;
  border-collapse: collapse;
}
.rating-table thead th {
  background: var(--color-surface-2);
  padding: var(--sp-2) var(--sp-4);
  text-align: left;
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--color-text-2);
  border-bottom: 1px solid var(--color-border);
}
.rating-table td {
  padding: var(--sp-2) var(--sp-4);
  border-bottom: 1px solid var(--color-border-subtle);
  font-size: 0.9375rem;
}
.rating-table td:first-child { font-weight: 600; color: var(--color-text); }
.rating-table tr:last-child td { border-bottom: none; }
.rating-badge {
  display: inline-block;
  font-weight: 700;
  font-size: 0.8125rem;
  padding: 2px var(--sp-2);
  border-radius: var(--radius-sm);
}
.rating-low { background: var(--color-success-surface); color: var(--color-success); }
.rating-medium { background: var(--color-warning-surface); color: var(--color-warning); }
.rating-high { background: var(--color-danger-surface); color: var(--color-danger); }

/* ============ Category / Taxonomy Page ============ */
.taxonomy-header {
  padding: var(--sp-12) 0 var(--sp-8);
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border-subtle);
  text-align: center;
}
.taxonomy-header h1 {
  font-size: clamp(1.5rem, 4vw, 2rem);
  font-weight: 800;
  color: var(--color-text);
  letter-spacing: -0.015em;
}
.taxonomy-header .count {
  color: var(--color-text-3);
  font-size: 0.9375rem;
  margin-top: var(--sp-2);
}
.taxonomy-header .breadcrumb {
  font-size: 0.8125rem;
  color: var(--color-text-3);
  margin-bottom: var(--sp-4);
}
.taxonomy-header .breadcrumb a { color: var(--color-accent); }

/* ============ Community CTA ============ */
.community {
  background: var(--color-surface);
  text-align: center;
}
.community h2 {
  color: var(--color-brand);
  font-size: clamp(1.5rem, 4vw, 2rem);
  font-weight: 800;
  margin-bottom: var(--sp-4);
  letter-spacing: -0.015em;
}
.community p {
  color: var(--color-text-2);
  max-width: 560px;
  margin: 0 auto var(--sp-8);
  font-size: 1rem;
  line-height: 1.6;
}
.community .hl { color: var(--color-brand); font-weight: 600; }

/* ============ Footer ============ */
.site-footer {
  background: var(--color-surface);
  padding: var(--sp-20) 0 var(--sp-10);
  border-top: 1px solid var(--color-border-subtle);
  margin-top: auto;
}

.footer-grid {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr 1fr;
  gap: var(--sp-10);
  margin-bottom: var(--sp-12);
}
.footer-brand,
.footer-brand-col { }
.footer-brand .logo,
.footer-brand-col .footer-logo { margin-bottom: var(--sp-3); font-weight: 900; font-size: 1.05rem; color: var(--color-brand); display: flex; align-items: center; gap: var(--sp-2); text-decoration: none; }
.footer-brand .logo:hover,
.footer-brand-col .footer-logo:hover { text-decoration: none; }
.footer-brand p,
.footer-tagline { color: var(--color-text-2); font-size: 0.9375rem; line-height: 1.6; max-width: 280px; }

.footer-col h4,
.footer-heading {
  font-size: 0.8125rem;
  font-weight: 700;
  color: var(--color-text-3);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: var(--sp-4);
}
.footer-col a {
  display: block;
  color: var(--color-text-2);
  font-size: 0.9375rem;
  padding: var(--sp-1) 0;
  transition: color 0.15s;
  text-decoration: none;
}
.footer-col a:hover { color: var(--color-text); text-decoration: none; }
.footer-links { list-style: none; padding: 0; margin: 0; }
.footer-links li { margin: 0; }
.footer-links a {
  display: block;
  color: var(--color-text-2);
  font-size: 0.9375rem;
  padding: var(--sp-1) 0;
  transition: color 0.15s;
  text-decoration: none;
}
.footer-links a:hover { color: var(--color-text); text-decoration: none; }

.footer-bottom {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding-top: var(--sp-8);
  border-top: 1px solid var(--color-border-subtle);
}
.footer-bottom .brand { font-weight: 700; color: var(--color-brand); font-size: 0.9375rem; }
.footer-bottom .copy,
.footer-copy { color: var(--color-text-3); font-size: 0.8125rem; }

/* Footer inner (legacy layout used by category/blog pages) */
.footer-inner {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--sp-10);
  margin-bottom: var(--sp-8);
}

/* Legacy footer (single-column) */
.site-footer .footer-cta { margin-bottom: var(--sp-6); text-align: center; }
.site-footer .footer-cta h3 { color: var(--color-brand); font-size: 1.125rem; margin-bottom: var(--sp-3); font-weight: 700; }
.footer-btns { display: flex; flex-wrap: wrap; gap: var(--sp-3); justify-content: center; }
.site-footer .brand { font-weight: 700; color: var(--color-brand); margin-bottom: var(--sp-1); text-align: center; }
.site-footer .copy { color: var(--color-text-3); font-size: 0.8125rem; text-align: center; }

/* ============ Beginner (新手村) ============ */
.beginner-hero { text-align: center; padding: var(--sp-20) 0 var(--sp-10); background: var(--color-bg); border-bottom: 1px solid var(--color-border-subtle); }
.beginner-hero h1 { font-size: clamp(2rem, 5vw, 2.5rem); color: var(--color-text); margin-bottom: var(--sp-3); font-weight: 800; letter-spacing: -0.02em; }
.beginner-hero .subtitle { font-size: 1.0625rem; color: var(--color-text-2); max-width: 580px; margin: 0 auto var(--sp-6); line-height: 1.7; }
.beginner-hero .badges { display: flex; gap: var(--sp-2); justify-content: center; flex-wrap: wrap; }
.beginner-hero .badge { background: var(--color-accent-surface); color: var(--color-accent); padding: var(--sp-1) var(--sp-3); border-radius: var(--radius-sm); font-size: 0.8125rem; font-weight: 600; }
.beginner-hero .breadcrumb { font-size: 0.8125rem; color: var(--color-text-3); margin-bottom: var(--sp-6); }
.beginner-hero .breadcrumb a { color: var(--color-accent); }

.path-section { padding: var(--sp-16) 0; }
.path-section:nth-child(even) { background: var(--color-surface); }
.path-header { display: flex; align-items: center; gap: var(--sp-4); margin-bottom: var(--sp-6); }
.path-num { width: 44px; height: 44px; border-radius: 50%; background: var(--color-brand); color: #fff; display: flex; align-items: center; justify-content: center; font-size: 1.25rem; font-weight: 800; flex-shrink: 0; }
.path-title { font-size: 1.5rem; font-weight: 700; color: var(--color-text); margin: 0; letter-spacing: -0.01em; }
.path-desc { color: var(--color-text-2); margin-bottom: var(--sp-6); font-size: 1rem; line-height: 1.7; }

.step-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: var(--sp-4); }
.step-card {
  background: var(--color-bg);
  border: 1px solid var(--color-border-subtle);
  border-radius: var(--radius-lg);
  padding: var(--sp-6);
  transition: box-shadow 0.15s, border-color 0.15s;
  text-decoration: none;
  color: inherit;
  display: flex;
  flex-direction: column;
  gap: var(--sp-2);
}
.step-card:hover { box-shadow: var(--shadow-md); border-color: var(--color-border); text-decoration: none; }
.step-order { font-size: 0.8125rem; color: var(--color-text-3); font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em; }
.step-name { font-size: 1rem; font-weight: 700; color: var(--color-text); }
.step-why { font-size: 0.875rem; color: var(--color-text-2); line-height: 1.6; }

.beginner-cta { text-align: center; padding: var(--sp-16) 0; background: var(--color-surface); }
.beginner-cta h2 { font-size: 1.5rem; color: var(--color-text); margin-bottom: var(--sp-3); font-weight: 700; }
.beginner-cta p { color: var(--color-text-2); margin-bottom: var(--sp-6); max-width: 480px; margin-left: auto; margin-right: auto; line-height: 1.7; }

/* ============ 404 ============ */
.page-404 {
  flex: 1;
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: var(--sp-20) var(--sp-6);
}
.page-404 h1 { font-size: 4rem; color: var(--color-brand); margin-bottom: var(--sp-3); }
.page-404 p { color: var(--color-text-2); margin-bottom: var(--sp-6); }

/* ============ Responsive ============ */
@media (max-width: 1024px) {
  .toc-sidebar { display: none; }
  .footer-grid { grid-template-columns: 1fr 1fr; }
}

@media (max-width: 768px) {
  .feature-grid { grid-template-columns: 1fr; gap: var(--sp-4); }
  .intent-grid { grid-template-columns: 1fr; }
  .tool-grid { grid-template-columns: repeat(3, 1fr); gap: var(--sp-3); }
  .diff-grid { grid-template-columns: 1fr; gap: var(--sp-4); }
  .topic-grid { grid-template-columns: repeat(2, 1fr); gap: var(--sp-2); }
  .article-grid { grid-template-columns: 1fr; }
  .related-grid { grid-template-columns: 1fr; }
  .security-rating-grid { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; gap: var(--sp-8); }
  .footer-bottom { flex-direction: column; gap: var(--sp-2); text-align: center; }
  section, .section { padding: var(--sp-16) 0; }
  .hero { padding: var(--sp-16) 0 var(--sp-12); }
  .container { padding: 0 var(--sp-4); }
  .article-nav { grid-template-columns: 1fr; }

  /* Mobile nav */
  .main-nav {
    display: none;
    flex-direction: column;
    position: absolute;
    top: var(--header-h); left: 0; right: 0;
    background: var(--color-bg);
    border-bottom: 1px solid var(--color-border-subtle);
    padding: var(--sp-4) var(--sp-6);
    gap: var(--sp-3);
    box-shadow: var(--shadow-lg);
    transform: translateY(-8px);
    opacity: 0;
    transition: transform 0.25s ease, opacity 0.25s ease;
  }
  .main-nav.open {
    display: flex;
    transform: translateY(0);
    opacity: 1;
  }
  .nav-toggle { display: flex; }

  .article-header h1 { font-size: 1.5rem; }
  .beginner-hero h1 { font-size: 1.75rem; }

  .topic-card { padding: var(--sp-3); }
  .topic-num { width: 36px; height: 36px; font-size: 0.8125rem; }
  .topic-name { font-size: 0.875rem; }
}

@media (max-width: 640px) {
  .topic-grid { grid-template-columns: 1fr; }
  .tool-grid { grid-template-columns: repeat(2, 1fr); }
  .hero-actions { flex-direction: column; align-items: center; }
  .hero-actions .btn { width: 100%; max-width: 300px; }
}