:root {
  --color-primary: #0b0b0f;
  --color-white: #ffffff;
  --color-gray-900: #111827;
  --color-gray-700: #374151;
  --color-gray-500: #6b7280;
  --color-gray-300: #d1d5db;
  --color-bg-soft: #f9fafb;

  --gradient-secondary: linear-gradient(135deg, #2563eb 0%, #22d3ee 100%);
  --gradient-tertiary: linear-gradient(135deg, #6366f1 0%, #a855f7 100%);

  --accent-fill: var(--color-primary);
  --accent-solid: var(--color-primary);

  --radius-s: 10px;
  --radius-m: 14px;

  --container-max: 1120px;
  --container-narrow: 820px;

  --section-gap: 72px;
  --transition-fast: 160ms ease;
}

@media (prefers-reduced-motion: reduce) {
  :root {
    --transition-fast: 0ms;
  }
}

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

html {
  color-scheme: light;
}

body {
  margin: 0;
  font-family: ui-sans-serif, system-ui, -apple-system, "Segoe UI", "Hiragino Sans",
    "Noto Sans JP", Arial, sans-serif;
  line-height: 1.8;
  color: var(--color-primary);
  background: var(--color-white);
  text-rendering: optimizeLegibility;

  --focus-outline: rgba(37, 99, 235, 0.35);
}

body[data-accent="tertiary"] {
  --accent-fill: var(--gradient-tertiary);
  --accent-solid: #6366f1;
  --focus-outline: rgba(99, 102, 241, 0.35);
}

body[data-accent="secondary"] {
  --accent-fill: var(--gradient-secondary);
  --accent-solid: #2563eb;
  --focus-outline: rgba(37, 99, 235, 0.35);
}

body[data-accent="mono"] {
  --accent-fill: var(--color-primary);
  --accent-solid: var(--color-primary);
  --focus-outline: rgba(17, 24, 39, 0.35);
}

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

.prose-image {
  margin: 18px 0;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-200);
  box-shadow: 0 10px 22px rgba(0, 0, 0, 0.08);
}

a {
  color: inherit;
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.22em;
}

a:hover {
  text-decoration-thickness: 2px;
}

:focus-visible {
  outline: 3px solid var(--focus-outline);
  outline-offset: 2px;
}

.skip-link {
  position: absolute;
  top: 8px;
  left: 8px;
  padding: 10px 12px;
  border-radius: var(--radius-s);
  background: var(--color-white);
  border: 1px solid var(--color-gray-300);
  transform: translateY(-200%);
  transition: transform var(--transition-fast);
}

.skip-link:focus {
  transform: translateY(0);
}

.container {
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: 24px;
}

.container--narrow {
  max-width: var(--container-narrow);
}

.section {
  padding-block: var(--section-gap);
}

.section--tight {
  padding-block: 40px;
}

.kicker {
  margin: 0;
  font-size: 13px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--color-gray-500);
}

.title {
  margin: 12px 0 0;
  font-size: clamp(24px, 3vw, 34px);
  line-height: 1.22;
  letter-spacing: -0.01em;
}

.lead {
  margin: 14px 0 0;
  max-width: 70ch;
  color: var(--color-gray-700);
}

.section-title {
  margin: 0;
  font-size: 22px;
  line-height: 1.25;
  letter-spacing: -0.01em;
}

.divider {
  height: 1px;
  background: var(--color-gray-300);
}

.accent-line {
  position: relative;
  padding-top: 14px;
}

.accent-line::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  width: 120px;
  height: 3px;
  border-radius: 999px;
  background: var(--accent-fill);
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 12px;
}

.meta-line {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--color-gray-300);
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  color: var(--color-gray-500);
  font-size: 13px;
}

.mt-12 {
  margin-top: 12px;
}

.mt-4 {
  margin-top: 4px;
}

.my-12 {
  margin-block: 12px;
}

.mt-18 {
  margin-top: 18px;
}

.mt-22 {
  margin-top: 22px;
}

.mt-24 {
  margin-top: 24px;
}

.text-body {
  color: var(--color-gray-700);
}

.text-muted {
  color: var(--color-gray-500);
}

.text-sm {
  font-size: 14px;
}

.font-semibold {
  font-weight: 650;
}

.no-underline {
  text-decoration: none;
}

.site-header {
  position: sticky;
  top: 0;
  z-index: 20;
  background: rgba(255, 255, 255, 0.88);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--color-gray-300);
}

.site-header__inner {
  display: flex;
  align-items: center;
  gap: 14px;
  padding-block: 14px;
}

.site-logo {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 650;
  letter-spacing: 0.02em;
  text-decoration: none;
  white-space: nowrap;
}

.global-nav {
  display: flex;
  align-items: center;
  gap: 2px;
  margin-left: auto;
}

.nav-link {
  padding: 8px 10px;
  border-radius: var(--radius-s);
  text-decoration: none;
  color: var(--color-gray-700);
  transition: background var(--transition-fast), color var(--transition-fast),
    border-color var(--transition-fast);
}

.nav-link:hover {
  background: var(--color-bg-soft);
  color: var(--color-primary);
}

.header-search {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-left: 10px;
}

.header-search input {
  width: 220px;
  padding: 10px 12px;
  border-radius: var(--radius-s);
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
}

.nav-drawer {
  display: none;
  margin-left: auto;
  position: relative;
}

.nav-drawer summary {
  cursor: pointer;
  list-style: none;
  padding: 8px 10px;
  border-radius: var(--radius-s);
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
}

.nav-drawer summary::-webkit-details-marker {
  display: none;
}

.nav-drawer__panel {
  position: absolute;
  right: 0;
  top: calc(100% + 10px);
  width: min(320px, calc(100vw - 48px));
  padding: 12px;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
}

.nav-drawer__panel nav {
  display: grid;
  gap: 6px;
}

.nav-drawer__panel .nav-link {
  padding: 10px 12px;
}

.nav-drawer__panel input[type="search"] {
  width: 100%;
  padding: 10px 12px;
  border-radius: var(--radius-s);
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
}

main {
  display: block;
}

.hero {
  position: relative;
  overflow: hidden;
  color: var(--color-white);
  padding-block: 96px 72px;
  background: var(--color-primary);
}

.hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image: url("../img/hero.jpg");
  background-size: cover;
  background-position: center;
  opacity: 0.14;
  filter: saturate(0) contrast(1.05);
}

.hero::after {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--accent-fill);
  opacity: 0.32;
}

.hero__inner {
  position: relative;
  z-index: 1;
}

.hero__kicker {
  margin: 0;
  font-size: 13px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: rgba(255, 255, 255, 0.78);
}

.hero__title {
  margin: 14px 0 0;
  font-size: clamp(30px, 3.8vw, 46px);
  line-height: 1.14;
  letter-spacing: -0.02em;
}

.hero__lead {
  margin: 16px 0 0;
  max-width: 70ch;
  color: rgba(255, 255, 255, 0.86);
}

.hero__actions {
  margin-top: 28px;
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 10px 14px;
  border-radius: var(--radius-s);
  border: 1px solid var(--color-gray-300);
  background: transparent;
  color: var(--color-primary);
  text-decoration: none;
  cursor: pointer;
  transition: background var(--transition-fast), border-color var(--transition-fast),
    color var(--transition-fast), filter var(--transition-fast);
}

.btn:hover {
  background: var(--color-bg-soft);
  border-color: rgba(17, 24, 39, 0.28);
}

.btn--primary {
  border-color: transparent;
  background: var(--accent-fill);
  color: var(--color-white);
}

.btn--primary:hover {
  background: var(--accent-fill);
  filter: brightness(0.96);
}

.btn--subtle {
  background: var(--color-white);
}

.btn[disabled] {
  cursor: not-allowed;
  opacity: 0.7;
}

.feature-visual {
  position: relative;
  overflow: hidden;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-primary);
  color: var(--color-white);
  padding: 40px 32px;
}

.feature-visual::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--accent-fill);
  opacity: 0.28;
}

.feature-visual::after {
  content: "";
  position: absolute;
  inset: 0;
  background-image: none;
  opacity: 0;
}

.feature-visual__inner {
  position: relative;
  z-index: 1;
  max-width: 70ch;
}

.feature-visual h2 {
  margin: 0;
  font-size: 22px;
  letter-spacing: -0.01em;
}

.feature-visual p {
  margin: 12px 0 0;
  color: rgba(255, 255, 255, 0.86);
}

.grid {
  display: grid;
  gap: 20px;
}

.grid--3 {
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.grid--2 {
  grid-template-columns: repeat(2, minmax(0, 1fr));
}

.card {
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
  padding: 18px;
  transition: background var(--transition-fast), border-color var(--transition-fast);
}

.card:hover {
  background: var(--color-bg-soft);
  border-color: rgba(17, 24, 39, 0.28);
}

.card a {
  text-decoration: none;
  display: flex;
  flex-direction: column;
  gap: 10px;
}

.card__image {
  width: 100%;
  height: auto;
  object-fit: contain;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
}

.card__title {
  margin: 0;
  font-size: 16px;
  line-height: 1.35;
  letter-spacing: -0.01em;
}

.card__desc {
  margin: 10px 0 0;
  color: var(--color-gray-700);
  font-size: 14px;
}

.card__meta {
  margin-top: 14px;
  padding-top: 12px;
  border-top: 1px solid var(--color-gray-300);
  color: var(--color-gray-500);
  font-size: 13px;
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.badge {
  display: inline-flex;
  align-items: center;
  padding: 4px 10px;
  border-radius: 999px;
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
  color: var(--color-gray-700);
  font-size: 12px;
  text-decoration: none;
}

.author-info {
  display: flex;
  align-items: center;
  gap: 8px;
  padding: 12px 16px;
  border-radius: var(--radius-s);
  background: var(--color-bg-soft);
  border: 1px solid var(--color-gray-300);
}

.author-label {
  font-size: 12px;
  color: var(--color-gray-500);
  font-weight: 500;
}

.author-name {
  font-size: 14px;
  color: var(--color-gray-700);
  font-weight: 600;
}

.article-thumbnail {
  width: 100%;
  max-width: 100%;
  height: auto;
  aspect-ratio: 16 / 9;
  object-fit: cover;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
}

.list-plain {
  list-style: none;
  padding: 0;
  margin: 18px 0 0;
  display: grid;
  gap: 10px;
}

.list-plain li {
  border: 1px solid var(--color-gray-300);
  border-radius: var(--radius-m);
  padding: 12px 14px;
  background: var(--color-white);
}

.stack {
  display: grid;
  gap: 12px;
}

.article-row {
  display: grid;
  gap: 10px;
  padding: 14px 0;
  border-top: 1px solid var(--color-gray-300);
}

.article-row:first-child {
  border-top: 0;
}

.article-row__meta {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  color: var(--color-gray-500);
  font-size: 13px;
}

.category-list {
  list-style: none;
  margin: 0;
  padding: 0;
  display: grid;
  gap: 12px;
}

.category-list li {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 14px 0;
  border-top: 1px solid var(--color-gray-300);
}

.category-list li:first-child {
  border-top: 0;
}

.category-list a {
  color: var(--color-gray-900);
  text-decoration: none;
  font-weight: 500;
}

.category-list a:hover {
  text-decoration: underline;
}

.category-count {
  color: var(--color-gray-500);
  font-size: 13px;
}

.category-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 16px;
  padding: 12px 0;
}

.category-button {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 24px 16px;
  border: 1px solid var(--color-gray-300);
  border-radius: 8px;
  background: #fff;
  text-decoration: none;
  color: var(--color-gray-900);
  font-weight: 500;
  transition: all 0.2s ease;
  min-height: 120px;
}

.category-button:hover {
  border-color: var(--color-primary);
  background: rgba(var(--color-primary-rgb), 0.05);
  transform: translateY(-2px);
  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
}

.category-button__label {
  font-size: 16px;
  font-weight: 600;
  text-align: center;
  line-height: 1.4;
}

.category-button__count {
  font-size: 12px;
  color: var(--color-gray-500);
}

.pagination {
  margin-top: 36px;
  display: flex;
  justify-content: center;
  gap: 10px;
}

.prose {
  font-size: 16px;
}

.prose p {
  margin: 18px 0;
}

.prose h2 {
  margin: 56px 0 0;
  scroll-margin-top: 96px;
  padding: 14px 14px 12px;
  border: 1px solid var(--color-gray-200);
  border-left: 4px solid var(--color-primary);
  border-radius: var(--radius-l);
  background: linear-gradient(90deg, rgba(var(--color-primary-rgb), 0.10), rgba(var(--color-primary-rgb), 0.02));
  box-shadow: 0 8px 18px rgba(0, 0, 0, 0.06);
  font-size: 22px;
  font-weight: 800;
  letter-spacing: -0.01em;
}

.prose h3 {
  margin: 34px 0 0;
  scroll-margin-top: 96px;
  padding-bottom: 8px;
  border-bottom: 2px solid rgba(var(--color-primary-rgb), 0.35);
  font-size: 18px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.prose h4 {
  margin: 22px 0 0;
  scroll-margin-top: 96px;
  padding-left: 12px;
  border-left: 2px solid var(--color-gray-300);
  color: var(--color-gray-900);
  font-size: 16px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.prose .toc {
  margin: 22px 0;
  padding: 14px 16px;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-bg-soft);
}

.prose .toc__title {
  font-weight: 700;
  letter-spacing: -0.01em;
}

.prose .toc__list {
  margin: 10px 0 0;
  padding-left: 1.2em;
}

.prose .toc__item {
  margin: 8px 0 0;
}

.prose .toc__item--h3 {
  margin-left: 1em;
  font-size: 0.95em;
}

.prose .toc__item--h4 {
  margin-left: 2em;
  font-size: 0.92em;
}

.prose ul,
.prose ol {
  margin: 18px 0;
  padding-left: 1.2em;
}

.prose li {
  margin-top: 8px;
}

.prose blockquote {
  margin: 22px 0;
  padding: 12px 14px;
  border-left: 3px solid var(--color-gray-300);
  background: var(--color-bg-soft);
  color: var(--color-gray-700);
}

.prose code {
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono",
    "Courier New", monospace;
  font-size: 0.95em;
}

.prose pre {
  margin: 18px 0;
  padding: 14px 16px;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-bg-soft);
  overflow: auto;
  line-height: 1.7;
}

.prose pre code {
  font-size: 13px;
}

.prose table {
  width: 100%;
  border-collapse: collapse;
  margin: 32px 0;
  font-size: 14px;
}

.prose thead {
  background-color: var(--color-gray-900);
  color: var(--color-white);
}

.prose th {
  padding: 12px 16px;
  text-align: left;
  font-weight: 600;
  border: 1px solid var(--color-gray-300);
  line-height: 1.5;
}

.prose td {
  padding: 12px 16px;
  border: 1px solid #e5e7eb;
  color: var(--color-gray-700);
}

.prose tbody tr:nth-child(even) {
  background-color: var(--color-bg-soft);
}

.prose tbody tr:hover {
  background-color: #f3f4f6;
}

.prose figure {
  margin: 32px 0;
  text-align: center;
}

.prose figure img {
  max-width: 100%;
  height: auto;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
}

.prose figcaption {
  margin-top: 8px;
  font-size: 13px;
  color: var(--color-gray-500);
  font-style: italic;
}

.callout {
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-bg-soft);
  padding: 14px 16px;
  color: var(--color-gray-700);
}

.author-box {
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  padding: 16px;
  display: flex;
  gap: 14px;
  align-items: flex-start;
  background: var(--color-white);
}

.author-avatar {
  width: 72px;
  height: 72px;
  border-radius: 50%;
  border: 1px solid var(--color-gray-300);
  object-fit: cover;
  flex: none;
}

.profile-header {
  display: flex;
  gap: 18px;
  align-items: flex-start;
  border-radius: var(--radius-m);
  border: 1px solid var(--color-gray-300);
  background: var(--color-white);
  padding: 18px;
}

.profile-avatar {
  width: 140px;
  height: 140px;
  border-radius: 50%;
  border: 1px solid var(--color-gray-300);
  object-fit: cover;
  flex: none;
}

.profile-meta {
  display: grid;
  gap: 10px;
}

.profile-name {
  margin: 0;
  font-size: 26px;
  line-height: 1.18;
  letter-spacing: -0.01em;
}

.profile-sub {
  color: var(--color-gray-700);
}

.profile-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.site-footer {
  margin-top: var(--section-gap);
  border-top: 1px solid var(--color-gray-300);
  padding-block: 28px;
}

.site-footer__inner {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  color: var(--color-gray-700);
  font-size: 14px;
}

.footer-nav {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.footer-nav a {
  text-decoration: none;
  padding: 6px 8px;
  border-radius: var(--radius-s);
}

.footer-nav a:hover {
  background: var(--color-bg-soft);
}

@media (max-width: 1023px) {
  .grid--3 {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }
}

@media (max-width: 767px) {
  :root {
    --section-gap: 56px;
  }

  .container {
    padding-inline: 16px;
  }

  .global-nav,
  .header-search {
    display: none;
  }

  .nav-drawer {
    display: block;
  }

  .hero {
    padding-block: 72px 56px;
  }

  .feature-visual {
    padding: 28px 18px;
  }

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

  .author-box {
    flex-direction: column;
  }

  .profile-header {
    flex-direction: column;
  }

  .profile-avatar {
    width: 120px;
    height: 120px;
  }
}

/* FAQ Section */
.faq-section {
  margin: 56px 0;
}

.faq-list {
  list-style: none;
  padding: 0;
  margin: 0;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.faq-item {
  border: 1px solid var(--color-gray-300);
  border-radius: var(--radius-m);
  overflow: hidden;
  background: var(--color-white);
  transition: all var(--transition-fast);
}

.faq-item:hover {
  border-color: var(--color-gray-500);
  box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
}

.faq-trigger {
  display: flex;
  width: 100%;
  padding: 16px;
  border: none;
  background: transparent;
  cursor: pointer;
  font-size: 15px;
  font-weight: 500;
  color: var(--color-primary);
  text-align: left;
  transition: background-color var(--transition-fast);
  align-items: center;
  gap: 8px;
  font-family: inherit;
  flex-wrap: wrap;
}

.faq-trigger:hover {
  background: var(--color-bg-soft);
}

.faq-trigger::before {
  content: "Q: ";
  font-weight: 600;
  flex: none;
}

.faq-trigger::after {
  content: "▼";
  margin-left: auto;
  font-size: 11px;
  transition: transform var(--transition-fast);
  flex: none;
  display: flex;
  align-items: center;
  order: 2;
}

.faq-item[open] .faq-trigger::after {
  transform: rotate(180deg);
}

.faq-content {
  padding: 16px;
  color: var(--color-gray-700);
  line-height: 1.7;
  font-size: 14px;
  border-top: 1px solid var(--color-gray-300);
}

.faq-content::before {
  content: "A: ";
  font-weight: 600;
  display: inline;
  margin-right: 0;
}

.faq-content p {
  margin: 0;
}

.faq-content p + p {
  margin-top: 12px;
}

.faq-content code {
  background: var(--color-bg-soft);
  padding: 2px 6px;
  border-radius: 4px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono",
    "Courier New", monospace;
  font-size: 13px;
}