:root {
  --color-primary: #1976d2;
  --color-primary-dark: #1565c0;
  --color-text: #222;
  --color-text-muted: #666;
  --color-border: #e0e0e0;
  --color-bg: #fafafa;
  --color-white: #fff;
  --container: 960px;
  --radius: 8px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

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

a { color: var(--color-primary); }
a:hover { color: var(--color-primary-dark); }

/* === Header === */
.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 32px;
  background: var(--color-white);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
  flex-wrap: wrap;
  gap: 12px;
}

.site-logo {
  font-size: 20px;
  font-weight: 700;
  color: var(--color-primary);
  text-decoration: none;
  letter-spacing: 0.02em;
}

.site-logo:hover { color: var(--color-primary-dark); }

.site-nav {
  display: flex;
  align-items: center;
  gap: 24px;
  font-size: 14px;
  flex-wrap: wrap;
}

.site-nav a {
  color: var(--color-text);
  text-decoration: none;
  transition: color 0.15s;
}

.site-nav a:hover { color: var(--color-primary); }

/* === Buttons === */
.btn {
  display: inline-block;
  padding: 10px 20px;
  font-size: 14px;
  font-weight: 500;
  border-radius: var(--radius);
  text-decoration: none;
  border: 1px solid var(--color-border);
  background: var(--color-white);
  color: var(--color-text);
  transition: background 0.15s, border-color 0.15s, color 0.15s;
  cursor: pointer;
  text-align: center;
  font-family: inherit;
}

.btn:hover {
  background: #f0f0f0;
  border-color: #b0b0b0;
  color: var(--color-text);
}

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

.btn--primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: var(--color-white);
}

.btn--small { padding: 6px 14px; font-size: 13px; }
.btn--large { padding: 14px 28px; font-size: 16px; }

/* === Main === */
.site-main {
  max-width: var(--container);
  margin: 0 auto;
  padding: 40px 24px 80px;
  width: 100%;
}

.site-main h1 {
  font-size: 40px;
  line-height: 1.2;
  margin: 0 0 20px;
  color: #111;
}

.site-main h2 {
  font-size: 26px;
  line-height: 1.3;
  margin: 48px 0 16px;
  color: #111;
  scroll-margin-top: 80px;
}

.site-main h3 {
  font-size: 19px;
  line-height: 1.3;
  margin: 28px 0 10px;
  color: #111;
}

.site-main p { margin: 0 0 16px; }
.site-main ul, .site-main ol { padding-left: 24px; margin: 0 0 16px; }
.site-main li { margin-bottom: 6px; }
.site-main strong { color: #000; }

/* === Hero === */
.hero {
  display: flex;
  flex-direction: column;
  align-items: center;
  text-align: center;
  padding: 20px 0 40px;
}

.hero h1 { font-size: 44px; }

.hero__lead {
  font-size: 18px;
  color: var(--color-text-muted);
  max-width: 720px;
  margin: 0 0 32px;
}

.hero__actions {
  display: flex;
  gap: 12px;
  justify-content: center;
  flex-wrap: wrap;
}

/* === Features === */
.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
  margin-top: 24px;
}

.feature {
  background: var(--color-white);
  padding: 24px;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
}

.feature h3 { margin-top: 0; color: var(--color-primary); }
.feature p { margin: 0; font-size: 15px; color: var(--color-text-muted); }

/* === Steps === */
.steps {
  list-style: none;
  counter-reset: step;
  padding: 0;
  margin: 24px 0 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 16px;
}

.steps > li {
  counter-increment: step;
  background: var(--color-white);
  padding: 24px;
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  position: relative;
}

.steps > li::before {
  content: counter(step);
  position: absolute;
  top: -12px;
  left: 24px;
  width: 28px;
  height: 28px;
  background: var(--color-primary);
  color: var(--color-white);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: 14px;
}

.steps h3 { margin-top: 8px; }
.steps p { margin: 0; font-size: 15px; color: var(--color-text-muted); }

/* === CTA === */
.cta {
  text-align: center;
  background: var(--color-white);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  padding: 48px 24px;
  margin-top: 48px;
}
.cta h2 { margin-top: 0; }

.cta-inline {
  text-align: center;
  background: var(--color-white);
  border-radius: var(--radius);
  border: 1px solid var(--color-border);
  padding: 32px 24px;
  margin-top: 48px;
}
.cta-inline p { font-size: 18px; margin: 0 0 16px; }

/* === Content === */
.content { max-width: 760px; margin: 0 auto; }
.lead {
  font-size: 18px;
  color: var(--color-text-muted);
  margin-bottom: 32px !important;
}

/* === TOC === */
.toc {
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin: 24px 0 40px;
}
.toc h2 { font-size: 18px; margin: 0 0 12px; }
.toc ul { margin: 0; padding-left: 20px; }
.toc li { margin-bottom: 4px; }

/* === Hotkeys table === */
.hotkeys {
  width: 100%;
  border-collapse: collapse;
  margin: 16px 0;
  font-size: 14px;
}
.hotkeys th, .hotkeys td {
  text-align: left;
  padding: 8px 12px;
  border-bottom: 1px solid var(--color-border);
}
.hotkeys th { background: var(--color-white); font-weight: 600; }
.hotkeys td:first-child {
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-weight: 600;
  white-space: nowrap;
}

/* === Articles === */
.articles-list {
  display: grid;
  gap: 16px;
  margin-top: 24px;
}

.article-preview {
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
}
.article-preview h2 { margin: 0 0 8px; font-size: 20px; }
.article-preview p { margin: 0 0 8px; color: var(--color-text-muted); font-size: 15px; }
.article-preview__meta { font-size: 13px; color: #999; font-style: italic; }

/* === Footer === */
.site-footer {
  background: var(--color-white);
  border-top: 1px solid var(--color-border);
  padding: 32px 24px;
  margin-top: 48px;
}

.site-footer__inner {
  max-width: var(--container);
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}
.site-footer__inner p { margin: 0; font-size: 13px; color: var(--color-text-muted); }
.site-footer__links { display: flex; gap: 20px; font-size: 13px; }
.site-footer__links a { color: var(--color-text-muted); text-decoration: none; }
.site-footer__links a:hover { color: var(--color-primary); }

/* === Media === */
@media (max-width: 768px) {
  .site-header { padding: 12px 16px; }
  .site-nav { gap: 16px; font-size: 13px; }
  .site-main { padding: 24px 16px 48px; }
  .site-main h1 { font-size: 30px; }
  .site-main h2 { font-size: 22px; margin-top: 32px; }
  .hero h1 { font-size: 30px; }
  .hero__lead { font-size: 16px; }
  .cta { padding: 32px 16px; }
  .site-footer__inner { flex-direction: column; text-align: center; }
}

/* === FAQ (details/summary) === */
.faq-list {
  margin-top: 24px;
}

.faq-item {
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  margin-bottom: 10px;
  overflow: hidden;
}

.faq-item summary {
  padding: 16px 48px 16px 20px;
  cursor: pointer;
  font-weight: 600;
  font-size: 16px;
  list-style: none;
  position: relative;
  color: var(--color-text);
  transition: color 0.15s;
}

.faq-item summary::-webkit-details-marker { display: none; }
.faq-item summary::marker { display: none; content: ''; }

.faq-item summary::after {
  content: '+';
  position: absolute;
  right: 20px;
  top: 50%;
  transform: translateY(-50%);
  font-size: 22px;
  line-height: 1;
  color: var(--color-primary);
  font-weight: 400;
}

.faq-item[open] summary::after {
  content: '−';
}

.faq-item summary:hover {
  color: var(--color-primary);
}

.faq-item[open] summary {
  border-bottom: 1px solid var(--color-border);
}

.faq-item__body {
  padding: 16px 20px;
  color: var(--color-text);
  line-height: 1.7;
}

.faq-item__body > :last-child { margin-bottom: 0; }

/* === Specs (definition list) === */
.specs {
  display: grid;
  grid-template-columns: minmax(180px, 1fr) 2fr;
  gap: 0;
  margin: 24px 0;
  background: var(--color-white);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  overflow: hidden;
}

.specs dt,
.specs dd {
  margin: 0;
  padding: 12px 16px;
  border-bottom: 1px solid var(--color-border);
  font-size: 15px;
}

.specs dt {
  font-weight: 600;
  background: #f5f5f5;
  color: var(--color-text);
}

.specs dd {
  color: var(--color-text-muted);
}

.specs dt:last-of-type,
.specs dd:last-of-type {
  border-bottom: none;
}

@media (max-width: 560px) {
  .specs {
    grid-template-columns: 1fr;
  }
  .specs dt {
    border-bottom: none;
    padding-bottom: 4px;
  }
  .specs dd {
    padding-top: 0;
  }
}