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

/* ── Light Theme ── */
:root,
[data-theme="light"] {
  --bg: #f0fbfc;
  --surface: #ffffff;
  --surface2: #e6f7f9;
  --border: #c8edf1;
  --accent: #98d7f2;
  --accent2: #2a9dbf;
  --accent3: #1a7a96;
  --accent-light: #e0f5fb;
  --text: #0d3d4d;
  --muted: #5a8a96;
  --hero-bg: #ffffff;
  --shadow-sm: 0 1px 4px rgba(40, 140, 170, .06);
  --shadow-md: 0 4px 20px rgba(40, 140, 170, .13);
  --shadow-lg: 0 6px 28px rgba(40, 140, 170, .18);
}

/* ── Dark Theme ── */
[data-theme="dark"] {
  --bg: #091820;
  --surface: #0e2530;
  --surface2: #153040;
  --border: #1e4558;
  --accent: #98d7f2;
  --accent2: #98d7f2;
  --accent3: #c5eaf8;
  --accent-light: rgba(152, 215, 242, .15);
  --text: #e0f5fb;
  --muted: #7ab8cc;
  --hero-bg: #0e2530;
  --shadow-sm: 0 1px 4px rgba(0, 0, 0, .25);
  --shadow-md: 0 4px 20px rgba(0, 0, 0, .35);
  --shadow-lg: 0 6px 28px rgba(0, 0, 0, .45);
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Segoe UI', 'Hiragino Sans', 'Meiryo', sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  overflow-x: hidden;
  transition: background .3s, color .3s;
}

/* ── Theme Toggle ── */
.theme-toggle {
  position: fixed;
  top: 80px;
  right: 20px;
  z-index: 1000;
  width: 48px;
  height: 48px;
  border-radius: 50%;
  border: 1.5px solid var(--border);
  background: var(--surface);
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  transition: background .3s, border-color .3s, transform .2s, box-shadow .2s;
}

.theme-toggle:hover {
  transform: scale(1.1) rotate(15deg);
  box-shadow: 0 6px 24px rgba(152, 215, 242, .35);
  border-color: var(--accent);
}

.theme-toggle svg {
  width: 20px;
  height: 20px;
  transition: opacity .3s, transform .3s;
  position: absolute;
}

.icon-sun {
  color: #f59e0b;
}

.icon-moon {
  color: #98d7f2;
}

[data-theme="light"] .icon-sun {
  opacity: 0;
  transform: rotate(90deg) scale(.6);
}

[data-theme="light"] .icon-moon {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

[data-theme="dark"] .icon-moon {
  opacity: 0;
  transform: rotate(-90deg) scale(.6);
}

[data-theme="dark"] .icon-sun {
  opacity: 1;
  transform: rotate(0deg) scale(1);
}

/* ── Hero ── */
.hero {
  position: relative;
  text-align: center;
  padding: 100px 24px 80px;
  background: var(--hero-bg);
  overflow: hidden;
  border-bottom: 1px solid var(--border);
  transition: background .3s, border-color .3s;
}

.hero::before {
  content: '';
  position: absolute;
  inset: 0;
  background:
    radial-gradient(ellipse 70% 60% at 50% -10%, rgba(152, 215, 242, .18) 0%, transparent 70%),
    radial-gradient(ellipse 40% 40% at 85% 90%, rgba(152, 215, 242, .10) 0%, transparent 60%);
  pointer-events: none;
}

[data-theme="dark"] .hero::before {
  background:
    radial-gradient(ellipse 70% 60% at 50% -10%, rgba(152, 215, 242, .22) 0%, transparent 70%),
    radial-gradient(ellipse 40% 40% at 85% 90%, rgba(152, 215, 242, .10) 0%, transparent 60%);
}

.hero::after {
  content: '';
  position: absolute;
  bottom: 0;
  left: 0;
  right: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
}

.hero-badge {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  background: var(--accent-light);
  border: 1px solid rgba(152, 215, 242, .4);
  border-radius: 999px;
  padding: 6px 16px;
  font-size: .78rem;
  font-weight: 700;
  letter-spacing: .08em;
  color: var(--accent3);
  text-transform: uppercase;
  margin-bottom: 24px;
  transition: background .3s;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3.6rem);
  font-weight: 800;
  letter-spacing: -.02em;
  line-height: 1.15;
  color: var(--text);
  margin-bottom: 16px;
  transition: color .3s;
}

[data-theme="dark"] .hero h1 span {
  background: linear-gradient(135deg, #98d7f2 0%, #c5eaf8 60%, #98d7f2 100%);
  -webkit-background-clip: text;
  background-clip: text;
}

.hero p {
  color: var(--muted);
  font-size: 1.05rem;
  max-width: 480px;
  margin: 0 auto 40px;
  line-height: 1.75;
  transition: color .3s;
}

/* ── Search ── */
.search-wrap {
  max-width: 520px;
  margin: 0 auto;
  position: relative;
}

.search-wrap svg {
  position: absolute;
  left: 18px;
  top: 50%;
  transform: translateY(-50%);
  color: var(--muted);
  width: 18px;
  height: 18px;
  pointer-events: none;
}

#search {
  width: 100%;
  background: var(--bg);
  border: 1.5px solid var(--border);
  border-radius: 999px;
  padding: 14px 20px 14px 48px;
  font-size: .97rem;
  color: var(--text);
  outline: none;
  transition: border-color .2s, box-shadow .2s, background .3s, color .3s;
  box-shadow: 0 2px 8px rgba(152, 215, 242, .1);
}

#search::placeholder {
  color: var(--muted);
  opacity: .7;
}

#search:focus {
  border-color: var(--accent);
  box-shadow: 0 0 0 4px rgba(152, 215, 242, .2);
  background: var(--surface);
}

/* ── Layout ── */
.main {
  max-width: 1100px;
  margin: 0 auto;
  padding: 56px 24px 100px;
  display: grid;
  grid-template-columns: 210px 1fr;
  gap: 40px;
  align-items: start;
}

/* ── Sidebar ── */
.sidebar {
  position: sticky;
  top: 32px;
}

.sidebar-title {
  font-size: .72rem;
  font-weight: 700;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 10px;
  padding-left: 4px;
  transition: color .3s;
}

.nav-list {
  list-style: none;
  display: flex;
  flex-direction: column;
  gap: 3px;
}

.nav-item button {
  width: 100%;
  text-align: left;
  background: none;
  border: none;
  padding: 9px 13px;
  border-radius: 10px;
  font-size: .88rem;
  color: var(--muted);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 9px;
  transition: background .15s, color .15s;
  font-family: inherit;
}

.nav-item button:hover,
.nav-item button.active {
  background: var(--accent-light);
  color: var(--accent2);
}

.nav-item button.active {
  font-weight: 600;
}

.nav-dot {
  width: 8px;
  height: 8px;
  border-radius: 50%;
  flex-shrink: 0;
}

.nav-count {
  margin-left: auto;
  font-size: .72rem;
  background: var(--surface2);
  padding: 1px 7px;
  border-radius: 999px;
  color: var(--muted);
  font-weight: 600;
  transition: background .3s, color .3s;
}

.nav-item button.active .nav-count {
  background: rgba(152, 215, 242, .25);
  color: var(--accent2);
}

/* ── FAQ Section ── */
.faq-section {
  display: flex;
  flex-direction: column;
  gap: 36px;
}

.section-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 14px;
}

.section-icon {
  width: 38px;
  height: 38px;
  border-radius: 11px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.1rem;
  flex-shrink: 0;
  box-shadow: var(--shadow-sm);
  transition: box-shadow .3s;
}

.section-title {
  font-size: 1rem;
  font-weight: 700;
}

.section-line {
  flex: 1;
  height: 1px;
  background: var(--border);
  transition: background .3s;
}

/* ── FAQ Item ── */
.faq-group {
  display: flex;
  flex-direction: column;
  gap: 0;
}

.faq-group > .faq-group-items {
  display: flex;
  flex-direction: column;
  gap: 8px;
}

.faq-item {
  background: var(--surface);
  border: 1.5px solid var(--border);
  border-radius: 16px;
  overflow: hidden;
  transition: border-color .2s, box-shadow .2s, transform .15s, background .3s;
  box-shadow: var(--shadow-sm);
}

.faq-item:hover {
  box-shadow: var(--shadow-md);
  transform: translateY(-1px);
}

.faq-item.open {
  box-shadow: var(--shadow-lg);
  transform: translateY(-1px);
}

.faq-btn {
  width: 100%;
  background: none;
  border: none;
  cursor: pointer;
  padding: 18px 20px;
  display: flex;
  align-items: center;
  gap: 13px;
  text-align: left;
  transition: background .15s;
}

.faq-btn:hover {
  background: rgba(152, 215, 242, .05);
}

.faq-item.open .faq-btn {
  background: rgba(152, 215, 242, .06);
}

.faq-q-icon {
  width: 34px;
  height: 34px;
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: .95rem;
  flex-shrink: 0;
  box-shadow: var(--shadow-sm);
}

.faq-q-text {
  flex: 1;
  font-size: .95rem;
  font-weight: 600;
  color: var(--text);
  line-height: 1.4;
  transition: color .3s;
}

.faq-chevron {
  width: 18px;
  height: 18px;
  color: var(--muted);
  transition: transform .3s ease, color .2s;
  flex-shrink: 0;
}

.faq-item.open .faq-chevron {
  transform: rotate(180deg);
  color: var(--accent2);
}

.faq-body {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows .32s ease;
}

.faq-item.open .faq-body {
  grid-template-rows: 1fr;
}

.faq-body-inner {
  overflow: hidden;
}

.faq-answer {
  padding: 16px 20px 20px 67px;
  font-size: .92rem;
  line-height: 1.85;
  color: var(--muted);
  border-top: 1px solid var(--border);
  transition: color .3s, border-color .3s, background .3s;
}

code {
  background: var(--accent-light);
  border: 1px solid rgba(152, 215, 242, .35);
  border-radius: 5px;
  padding: 1px 7px;
  font-family: 'Consolas', 'Courier New', monospace;
  font-size: .84em;
  color: var(--accent3);
  transition: background .3s, color .3s;
}

strong {
  color: var(--text);
  font-weight: 600;
  transition: color .3s;
}

/* ── Category colors ── */
.cat-patch { --c: #e879a0; --cl: #fdf0f6; --cl-dark: rgba(232, 121, 160, .13); }
.cat-ui    { --c: #2ab899; --cl: #edfaf6; --cl-dark: rgba(42, 184, 153, .13); }
.cat-code  { --c: #e8a020; --cl: #fef8ec; --cl-dark: rgba(232, 160, 32, .13); }
.cat-text  { --c: #98d7f2; --cl: #e8f7fd; --cl-dark: rgba(152, 215, 242, .15); }
.cat-relay { --c: #2a9dbf; --cl: #e6f6fb; --cl-dark: rgba(42, 157, 191, .13); }
.cat-multi { --c: #f47b40; --cl: #fef3ec; --cl-dark: rgba(244, 123, 64, .13); }
.cat-error { --c: #e85555; --cl: #fef0f0; --cl-dark: rgba(232, 85, 85, .13); }

[class*="cat-"] .section-icon {
  background: var(--cl);
  color: var(--c);
  border: 1px solid color-mix(in srgb, var(--c) 20%, transparent);
}

[data-theme="dark"] [class*="cat-"] .section-icon {
  background: var(--cl-dark);
}

[class*="cat-"] .section-title {
  color: var(--c);
}

[class*="cat-"] .faq-q-icon {
  background: var(--cl);
  color: var(--c);
  border: 1px solid color-mix(in srgb, var(--c) 15%, transparent);
}

[data-theme="dark"] [class*="cat-"] .faq-q-icon {
  background: var(--cl-dark);
}

[class*="cat-"] .faq-item.open {
  border-color: color-mix(in srgb, var(--c) 38%, transparent);
}

[class*="cat-"] .faq-item.open .faq-chevron {
  color: var(--c);
}

[class*="cat-"] .faq-item.open .faq-answer {
  border-top-color: color-mix(in srgb, var(--c) 18%, transparent);
}

[data-theme="light"] [class*="cat-"] .faq-item.open .faq-answer {
  background: color-mix(in srgb, var(--c) 3%, #fff);
}

[class*="cat-"] .faq-item:hover {
  box-shadow: 0 4px 20px color-mix(in srgb, var(--c) 18%, transparent);
}

/* ── Empty state ── */
.empty {
  text-align: center;
  padding: 80px 24px;
  color: var(--muted);
  display: none;
}

.empty.show {
  display: block;
}

.empty-icon {
  font-size: 3rem;
  margin-bottom: 16px;
}

.empty h3 {
  font-size: 1.1rem;
  margin-bottom: 8px;
  color: var(--text);
}

/* ── Responsive ── */
@media (max-width: 760px) {
  .main {
    grid-template-columns: 1fr;
    gap: 24px;
  }

  .sidebar {
    position: static;
  }

  .nav-list {
    flex-direction: row;
    flex-wrap: wrap;
  }

  .nav-item button {
    padding: 7px 11px;
    font-size: .82rem;
  }

  .hero {
    padding: 64px 16px 56px;
  }

  .faq-answer {
    padding-left: 20px;
  }

  .theme-toggle {
    top: 90px;
    right: 12px;
    width: 42px;
    height: 42px;
  }
}

/* ── Tags ── */
.faq-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  padding: 0 20px 16px 67px;
}

.tag {
  display: inline-flex;
  align-items: center;
  background: var(--surface2);
  border: 1px solid var(--border);
  border-radius: 999px;
  padding: 2px 10px;
  font-size: .72rem;
  font-weight: 600;
  color: var(--muted);
  transition: background .3s, color .3s, border-color .3s;
}