:root {
  --bg: #edede9;
  --surface: #e0e0d2;
  --text: #0b0b0f;
  --muted: #4a4a55;
  --primary: #c28739;
  --accent: #3f41ae;
  --shelff-blue: #3b5998;
  --shelff-blue-light: #c8d4e8;
  --max-page-width: 60rem;
}

body {
  background-color: var(--bg);
  color: var(--text);
  font-family: "Hiragino Kaku Gothic ProN", "Noto Sans JP", system-ui, sans-serif;
  line-height: 1.8;
  margin: 0;
}

:lang(en) {
  line-height: 1.5;
}

main {
  max-width: var(--max-page-width);
  margin-inline: auto;
  padding-inline: 1rem;
}

h1, h2, h3 {
  margin-top: 2rem;
  margin-bottom: 0;
}
h1 a, h1 a:visited, h2 a, h2 a:visited, h3 a, h3 a:visited {
  color: var(--text);
  text-decoration: none;
}
h1 a:hover, h1 a:visited:hover, h2 a:hover, h2 a:visited:hover, h3 a:hover, h3 a:visited:hover {
  color: var(--accent);
  text-decoration: underline;
}

p {
  margin-block-start: 0.5rem;
}

a {
  color: var(--accent);
}

a:visited {
  color: color-mix(in oklab, var(--accent), var(--text) 25%);
}

h1 {
  color: var(--primary);
}

small,
.muted {
  color: var(--muted);
}

blockquote,
pre {
  background-color: var(--surface);
  padding: 1rem;
}

blockquote {
  border-inline-start: 3px solid var(--primary);
}

svg.icon {
  width: 1em;
  height: 1em;
  vertical-align: -0.1em;
  fill: currentColor;
}

pre {
  overflow-x: auto;
  line-height: 1.5;
  font-size: 0.875rem;
}

code {
  font-family: "SF Mono", "Menlo", "Consolas", monospace;
  font-size: 0.9em;
}

section.toppage-about > p {
  margin-block-start: 2em;
}

section.division header {
  border-bottom: 1px solid var(--primary);
  padding-bottom: 0.5rem;
}
section.division header h2 {
  margin-top: 0;
}
section.division header p {
  margin-block-start: 0.2rem;
  margin-block-end: 0;
}
section.division header {
  margin-bottom: 1rem;
}
section.division article h3 {
  margin-top: 0.75rem;
}
section.division {
  margin-top: 3rem;
}

header#main-header {
  padding-inline: 1rem;
  background-color: var(--surface);
  padding-block: 1rem;
}
header#main-header > .header-inner {
  max-width: var(--max-page-width);
  margin-inline: auto;
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0 1rem;
  position: relative;
}
header#main-header h1 {
  margin-top: 0;
}
header#main-header > * {
  max-width: var(--max-page-width);
  margin-inline: auto;
}

.site-name a,
.site-name a:visited {
  color: var(--primary);
}

/* ---- site nav ---- */
.site-nav {
  margin-left: auto;
}

.nav-toggle {
  display: none;
}

.nav-menu {
  display: flex;
  align-items: center;
  gap: 0;
}

.nav-links {
  display: flex;
  gap: 0.75rem;
}

.nav-links a {
  color: var(--accent);
  text-decoration: none;
}

.nav-links a:hover {
  text-decoration: underline;
}

.nav-links a[aria-current=page] {
  color: var(--text);
  text-decoration: none;
}

.lang-links {
  display: flex;
  align-items: center;
  gap: 0.35rem;
  margin-left: 0.75rem;
  padding-left: 0.75rem;
  border-left: 1px solid var(--muted);
  font-size: 0.8rem;
}

.lang-links a {
  color: var(--accent);
  text-decoration: none;
}

.lang-links a:visited {
  color: var(--accent);
}

.lang-links a:hover {
  color: var(--accent);
  text-decoration: underline;
}

.lang-sep {
  color: var(--muted);
  font-size: 0.75rem;
}

.lang-current {
  color: var(--text);
}

/* ---- hamburger button ---- */
.nav-toggle {
  background: none;
  border: none;
  cursor: pointer;
  padding: 0.25rem;
}

.hamburger,
.hamburger::before,
.hamburger::after {
  display: block;
  width: 1.25rem;
  height: 2px;
  background-color: var(--text);
  transition: transform 0.2s, opacity 0.2s;
}

.hamburger {
  position: relative;
}

.hamburger::before,
.hamburger::after {
  content: "";
  position: absolute;
  left: 0;
}

.hamburger::before {
  top: -6px;
}

.hamburger::after {
  top: 6px;
}

.nav-toggle[aria-expanded=true] .hamburger {
  background-color: transparent;
}

.nav-toggle[aria-expanded=true] .hamburger::before {
  top: 0;
  transform: rotate(45deg);
}

.nav-toggle[aria-expanded=true] .hamburger::after {
  top: 0;
  transform: rotate(-45deg);
}

/* ---- responsive nav ---- */
@media (max-width: 600px) {
  .nav-toggle {
    display: block;
  }
  .nav-menu {
    display: none;
    flex-direction: column;
    align-items: flex-start;
    gap: 0.5rem;
    position: absolute;
    top: 100%;
    right: 0;
    z-index: 100;
    background-color: var(--surface);
    padding: 0.75rem 1rem;
    border-radius: 0 0 6px 6px;
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
    min-width: 8rem;
  }
  .nav-toggle[aria-expanded=true] + .nav-menu {
    display: flex;
  }
  .nav-links {
    flex-direction: column;
    gap: 0.25rem;
  }
  .lang-links {
    margin-left: 0;
    padding-left: 0;
    border-left: none;
    padding-top: 0.25rem;
    border-top: 1px solid var(--muted);
  }
}
footer {
  max-width: var(--max-page-width);
  margin-inline: auto;
  padding-inline: 1rem;
  padding-block: 2rem 1rem;
  margin-top: 3rem;
  border-top: 1px solid var(--surface);
  color: var(--muted);
  font-size: 0.875rem;
}

footer p {
  margin-block: 0.25rem;
}

footer a {
  color: var(--muted);
}

footer a:hover {
  color: var(--accent);
}

.shelff-hero {
  text-align: center;
  padding-block: 3rem 2rem;
}

.shelff-hero .app-icon {
  width: 128px;
  height: 128px;
  border-radius: 28px;
  box-shadow: 0 4px 20px rgba(59, 89, 152, 0.2);
}

.shelff-hero h2 {
  font-size: 2rem;
  margin-top: 1.25rem;
  margin-bottom: 0;
  letter-spacing: 0.05em;
  color: var(--text);
}

.shelff-hero .tagline {
  font-size: 1.05rem;
  color: var(--muted);
  margin-top: 0.5rem;
}

.shelff-hero .cta-area {
  margin-top: 1.25rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.5rem;
}

.shelff-hero .cta-button {
  display: inline-block;
  font-size: 0.9rem;
  color: #fff;
  background-color: var(--shelff-blue);
  padding: 0.5em 1.5em;
  border-radius: 2em;
  text-decoration: none;
  transition: background-color 0.15s;
}

.shelff-hero .cta-button:visited {
  color: #fff;
}

.shelff-hero .cta-button:hover {
  background-color: #2d4a80;
}

.shelff-hero .pricing-note {
  font-size: 0.8rem;
  color: var(--muted);
}

.shelff-features {
  margin-top: 2rem;
}

.shelff-features h3 {
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--muted);
  border-bottom: 1px solid var(--surface);
  padding-bottom: 0.4rem;
  margin-top: 2.5rem;
  margin-bottom: 1rem;
}

.feature {
  margin-bottom: 1.5rem;
}

.feature dt {
  font-weight: bold;
  font-size: 1rem;
  margin-bottom: 0.2rem;
}

.feature dd {
  margin-left: 0;
  color: var(--muted);
  font-size: 0.95rem;
  line-height: 1.7;
}

.spec-link {
  margin-top: 3rem;
  padding: 1rem 1.25rem;
  background-color: var(--surface);
  border-radius: 6px;
  font-size: 0.9rem;
}

.spec-link a {
  color: var(--accent);
}

.spec-toc {
  margin-top: 2rem;
  padding: 1rem 1.25rem;
  background-color: var(--surface);
  border-radius: 6px;
}

.spec-toc h3 {
  margin-top: 0;
  font-size: 0.9rem;
}

.spec-toc ol {
  margin-bottom: 0;
  padding-left: 1.25rem;
}

.spec-toc a {
  color: var(--accent);
}

.spec-section {
  margin-top: 3rem;
}

.spec-section h3 {
  font-size: 1.2rem;
  border-bottom: 1px solid var(--primary);
  padding-bottom: 0.4rem;
}

.spec-section h4 {
  margin-top: 1.5rem;
  margin-bottom: 0.5rem;
  font-size: 1rem;
}

.spec-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.9rem;
  margin-top: 0.75rem;
}

.spec-table th,
.spec-table td {
  text-align: left;
  padding: 0.5rem 0.75rem;
  border-bottom: 1px solid var(--surface);
  vertical-align: top;
}

.spec-table th {
  color: var(--muted);
  font-weight: normal;
  font-size: 0.8rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.spec-table code {
  font-size: 0.85em;
}