/* xdo — minimal black & white, light/dark */

:root,
[data-theme="light"] {
  --bg: #ffffff;
  --fg: #0a0a0a;
  --muted: #6b6b6b;
  --line: #e4e4e4;
  --card: #fafafa;
  --accent: #0a0a0a;
  color-scheme: light;
}

[data-theme="dark"] {
  --bg: #0a0a0a;
  --fg: #f2f2f2;
  --muted: #9a9a9a;
  --line: #2b2b2b;
  --card: #141414;
  --accent: #f2f2f2;
  color-scheme: dark;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
}

body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue",
    "PingFang HK", "Noto Sans HK", "Microsoft JhengHei", sans-serif;
  font-size: 1.0625rem;
  line-height: 1.65;
  color: var(--fg);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
}

.wrap {
  max-width: 68.75rem;
  margin: 0 auto;
  padding: 0 1.5rem;
}

a {
  color: var(--fg);
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
}

a:hover {
  text-decoration: underline;
}

img {
  display: inline-block;
  vertical-align: middle;
}

/* logos switch with the theme */
.logo-white {
  display: none;
}
[data-theme="dark"] .logo-black {
  display: none;
}
[data-theme="dark"] .logo-white {
  display: inline-block;
}

/* header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--bg);
  border-bottom: 1px solid var(--line);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 4rem;
}

.brand .logo {
  height: 1.75rem;
  width: auto;
}

.site-nav {
  display: flex;
  align-items: center;
  gap: 1.4rem;
  font-size: 0.95rem;
}

.site-nav a {
  text-decoration: none;
}

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

.nav-sep {
  width: 1px;
  height: 1.1rem;
  background: var(--line);
}

.lang-link {
  font-weight: 600;
}

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 2.1rem;
  height: 2.1rem;
  padding: 0;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: transparent;
  color: var(--fg);
  cursor: pointer;
}

.theme-toggle svg {
  width: 1rem;
  height: 1rem;
  fill: none;
  stroke: currentColor;
  stroke-width: 2;
}

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

.nav-toggle {
  display: none;
  font-size: 0.95rem;
  font-weight: 600;
  padding: 0.45rem 0.9rem;
  border: 1px solid var(--line);
  background: transparent;
  color: var(--fg);
  border-radius: 0.25rem;
  cursor: pointer;
}

/* hero */
.hero {
  padding: clamp(4rem, 10vw, 8rem) 0 clamp(3rem, 6vw, 5rem) 0;
}

.eyebrow {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 1.5rem;
}

.hero-title {
  font-size: clamp(2.4rem, 6.5vw, 4.5rem);
  font-weight: 800;
  letter-spacing: -0.03em;
  line-height: 1.04;
  margin: 0 0 1.5rem;
  text-wrap: balance;
}

.lead {
  font-size: clamp(1.1rem, 2vw, 1.3rem);
  max-width: 42rem;
  color: var(--muted);
  margin: 0 0 2.5rem;
}

.cta-row {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin: 0 0 1rem;
}

.btn {
  display: inline-block;
  padding: 0.75rem 1.5rem;
  border: 1px solid var(--fg);
  border-radius: 0.25rem;
  text-decoration: none;
  font-weight: 600;
  font-size: 0.95rem;
}

.btn-primary {
  background: var(--fg);
  color: var(--bg);
}

.btn:hover {
  text-decoration: none;
  opacity: 0.85;
}

/* sections */
.section {
  padding: clamp(3rem, 7vw, 5.5rem) 0;
}

.section-alt {
  background: var(--card);
}

.section-label {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.8rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.75rem;
}

.section-title {
  font-size: clamp(1.6rem, 3.5vw, 2.4rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.15;
  margin: 0 0 1rem;
  max-width: 36rem;
}

.section-intro {
  color: var(--muted);
  max-width: 42rem;
  margin: 0 0 2.5rem;
}

.sub-title {
  font-size: 0.8rem;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.75rem;
  font-weight: 500;
}

/* service cards */
.cards {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1.25rem;
}

.card {
  border: 1px solid var(--line);
  border-radius: 0.4rem;
  padding: 1.75rem;
  background: var(--bg);
}

.card-tag {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.9rem;
}

.card h3 {
  font-size: 1.3rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 0 0 0.75rem;
}

.card p {
  margin: 0 0 0.9rem;
  color: var(--muted);
}

.card .who {
  font-size: 0.95rem;
}

.card .benefit {
  border-top: 1px solid var(--line);
  padding-top: 0.9rem;
  color: var(--fg);
}

.card .benefit strong {
  display: block;
  font-size: 0.8rem;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.35rem;
}

/* note / certificate wording */
.note {
  margin-top: 2rem;
  border-left: 3px solid var(--fg);
  padding: 0.25rem 0 0.25rem 1.25rem;
  max-width: 46rem;
}

.note h3 {
  font-size: 0.8rem;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 0.5rem;
}

.note p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

/* approach steps */
.steps {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 1.25rem;
  counter-reset: step;
}

.step {
  border: 1px solid var(--line);
  border-radius: 0.4rem;
  padding: 1.5rem;
  background: var(--bg);
}

.step-num {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.8rem;
  color: var(--muted);
  margin: 0 0 0.75rem;
}

.step h3 {
  margin: 0 0 0.5rem;
  font-size: 1.05rem;
  font-weight: 700;
}

.step p {
  margin: 0;
  color: var(--muted);
  font-size: 0.95rem;
}

/* about */
.about-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 2.5rem;
}

.cred-list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.cred-list li {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.95rem;
  padding: 0.5rem 0;
  border-bottom: 1px solid var(--line);
}

/* contact */
.contact-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2rem;
  margin-bottom: 2.5rem;
}

.contact-grid p {
  margin: 0 0 0.4rem;
}

.contact-link {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.98rem;
}

.placeholder {
  color: var(--muted);
  border: 1px dashed var(--line);
  border-radius: 0.25rem;
  display: inline-block;
  padding: 0.15rem 0.6rem;
  font-size: 0.9rem;
}

/* articles */
.breadcrumb {
  font-size: 0.9rem;
  margin: 1.75rem 0 2rem;
}

.page-title {
  font-size: clamp(1.8rem, 4vw, 2.8rem);
  font-weight: 800;
  letter-spacing: -0.02em;
  line-height: 1.1;
  margin: 0 0 0.75rem;
  max-width: 40rem;
}

.article-list {
  list-style: none;
  margin: 0 0 4rem;
  padding: 0;
}

.article-list li {
  border-bottom: 1px solid var(--line);
  padding: 1.5rem 0;
}

.article-list h2 {
  margin: 0 0 0.35rem;
  font-size: 1.25rem;
  font-weight: 700;
}

.article-list h2 a {
  text-decoration: none;
}

.article-list h2 a:hover {
  text-decoration: underline;
}

.article-list .meta {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.8rem;
  color: var(--muted);
  margin: 0 0 0.5rem;
}

.article-list p {
  margin: 0;
  color: var(--muted);
}

/* article body */
.article {
  padding-bottom: 4rem;
}

.article-body {
  max-width: 44rem;
  font-size: 1.05rem;
}

.article-body h2 {
  font-size: 1.45rem;
  font-weight: 700;
  letter-spacing: -0.01em;
  margin: 2.5rem 0 0.75rem;
}

.article-body h3 {
  font-size: 1.15rem;
  font-weight: 700;
  margin: 2rem 0 0.5rem;
}

.article-body pre {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 0.4rem;
  padding: 1rem 1.25rem;
  overflow-x: auto;
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.9rem;
  line-height: 1.55;
}

.article-body code {
  font-family: ui-monospace, "SF Mono", Menlo, Consolas, "Courier New",
    monospace;
  font-size: 0.92em;
}

.article-body p code,
.article-body li code {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 0.2rem;
  padding: 0.08em 0.35em;
}

.article-body blockquote {
  border-left: 3px solid var(--fg);
  margin: 1.5rem 0;
  padding: 0.25rem 0 0.25rem 1.25rem;
  color: var(--muted);
}

/* footer */
.site-footer {
  border-top: 1px solid var(--line);
  padding: 2.5rem 0;
  margin-top: 2rem;
}

.footer-inner {
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 1.5rem;
  align-items: center;
}

.footer-brand .logo {
  height: 2.25rem;
  width: auto;
}

.footer-tagline {
  font-size: 0.9rem;
  color: var(--muted);
  margin: 0.5rem 0 0;
}

.footer-meta {
  font-size: 0.85rem;
  color: var(--muted);
  text-align: right;
}

.footer-meta p {
  margin: 0 0 0.35rem;
}

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

/* responsive */
@media (max-width: 56rem) {
  .cards,
  .steps,
  .about-grid,
  .contact-grid {
    grid-template-columns: 1fr;
  }

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

@media (max-width: 40rem) {
  .steps {
    grid-template-columns: 1fr;
  }

  .footer-meta {
    text-align: left;
  }

  .nav-toggle {
    display: inline-block;
  }

  .site-nav {
    display: none;
    position: absolute;
    top: 100%;
    left: 0;
    right: 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 1rem;
    background: var(--bg);
    border-bottom: 1px solid var(--line);
    padding: 1.25rem 1.5rem 1.75rem;
  }

  .nav-open .site-nav {
    display: flex;
  }

  .nav-sep {
    display: none;
  }
}