:root {
  --bg: #ffffff;
  --fg: #2f3437;
  --fg-dim: #6b6f76;
  --border: #e6e7e9;
  --callout: #f6f7f8;
  --accent: #3b5bdb;
  --accent-dim: #6475ff;
  --code-bg: #f4f5f7;
  --quote: #e6e7e9;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1113;
    --fg: #e6e6e6;
    --fg-dim: #a3a7ac;
    --border: #2b2f34;
    --callout: #171a1d;
    --accent: #7ea1ff;
    --accent-dim: #9cb6ff;
    --code-bg: #15181b;
    --quote: #2b2f34;
  }
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, Helvetica, Arial, "Apple Color Emoji", "Segoe UI Emoji";
  background: var(--bg);
  color: var(--fg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  scroll-behavior: smooth;
}

.page {
  display: grid;
  grid-template-columns: minmax(12px, 1fr) minmax(0, 760px) minmax(12px, 1fr) minmax(0, 280px);
  gap: 0 24px;
}

header.cover {
  grid-column: 1 / -1;
  width: 100%;
  height: auto;
  border-bottom: 1px solid var(--border);
  overflow: hidden;
}

header.cover img {
  display: block;
  width: 100%;
  height: auto;
  object-fit: cover;
}

.header-inner {
  grid-column: 2 / 3;
  margin-top: 16px;
  display: flex;
  align-items: center;
  gap: 16px;
}

.page-icon {
  width: 72px; height: 72px;
  border-radius: 12px;
  display: grid; place-items: center;
  font-size: 40px;
  background: var(--bg);
  box-shadow: 0 2px 8px rgba(0,0,0,0.08);
  border: 1px solid var(--border);
}

h1.title {
  font-size: 40px;
  font-weight: 800;
  letter-spacing: -0.02em;
  margin: 0;
  color: var(--fg);
}

main {
  grid-column: 2 / 3;
  padding: 24px 0 64px;
}

.meta {
  color: var(--fg-dim);
  font-size: 14px;
  margin-top: 2px;
  line-height: 1.3;
}

.content h2 { font-size: 28px; margin: 32px 0 8px; line-height: 1.3; }
.content h3 { font-size: 20px; margin: 20px 0 6px; line-height: 1.35; }
.content p { margin: 8px 0 12px; }
.content ul, .content ol { padding-left: 22px; margin: 8px 0 16px; }
.content li { margin: 6px 0; }
.content hr { border: none; border-top: 1px solid var(--border); margin: 24px 0; }

.callout {
  display: flex; gap: 12px; align-items: flex-start;
  padding: 14px 16px;
  background: var(--callout);
  border: 1px solid var(--border);
  border-radius: 8px;
  margin: 12px 0 16px;
}
.callout .icon { font-size: 20px; line-height: 1; }

.checklist { list-style: none; padding-left: 0; }
.checklist li { display: flex; gap: 10px; align-items: flex-start; }
.checklist input[type="checkbox"] { margin-top: 4px; }

pre.code { background: transparent; border: none; border-radius: 0; padding: 0; overflow: auto; font-size: 14px; line-height: 1.5; }
code.inline { background: var(--code-bg); padding: 2px 6px; border-radius: 6px; border: 1px solid var(--border); }

blockquote { border-left: 3px solid var(--quote); margin: 12px 0; padding: 2px 0 2px 12px; color: var(--fg-dim); }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

aside.toc {
  grid-column: 4 / 5;
  position: sticky; top: 24px;
  align-self: start;
  margin: 24px 0 64px;
  background: var(--callout);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 12px;
  max-height: calc(100vh - 48px);
  overflow: auto;
}
.toc .title { font-weight: 700; font-size: 12px; letter-spacing: 0.06em; color: var(--fg-dim); text-transform: uppercase; margin: 4px 0 8px; padding-left: 4px; }
.toc nav { padding: 0; }
.toc ul { list-style: none; margin: 0; padding: 0; }
.toc li { margin: 4px 0; }
.toc a { display: block; padding: 4px 8px 4px 12px; border-radius: 6px; color: var(--fg-dim); border: 1px solid transparent; }
.toc a.level-2 { padding-left: 12px; }
.toc a.level-3 { padding-left: 24px; font-size: 13px; }
.toc a.active { color: var(--fg); background: var(--callout); border-color: var(--border); text-decoration: none; }

.back-to-top { display: inline-flex; align-items: center; gap: 6px; font-size: 14px; color: var(--fg-dim); }

.footer { grid-column: 2 / 3; border-top: 1px solid var(--border); padding: 16px 0 40px; color: var(--fg-dim); font-size: 14px; }

@media (max-width: 1200px) {
  .page { grid-template-columns: 12px minmax(0, 760px) 12px 0; }
  aside.toc { display: none; }
}
@media (max-width: 780px) {
  h1.title { font-size: 32px; }
  header.cover { height: 200px; }
  .page { grid-template-columns: 10px minmax(0, 1fr) 10px 0; }
  .header-inner { margin-top: 12px; }
  .page-icon { width: 64px; height: 64px; font-size: 34px; }
}

:target {
  scroll-margin-top: 84px;
}

details.toggle {
  border: none;
  border-radius: 0;
  padding: 0;
  background: transparent;
  margin: 10px 0 14px;
}

details.toggle > summary {
  cursor: pointer;
  list-style: none;
  font-weight: 600;

  color: inherit;
  text-decoration: none;
  user-select: none;

  position: relative;
  padding-left: 1.2em;
}

details.toggle > summary::-webkit-details-marker {
  display: none;
}

details.toggle > summary::before {
  content: "▶";
  position: absolute;
  left: 0;
  top: 0;
  transition: transform 0.2s ease;
  font-size: 0.9em;
}

details.toggle[open] > summary::before {
  transform: rotate(90deg);
}

details.toggle {
  border: none;
  border-radius: 0;
  padding: 0;
  background: transparent;
  margin: 10px 0 14px;
}
details.toggle > summary {
  cursor: pointer;
  list-style: none;
  font-weight: 600;
}
details.toggle > summary::-webkit-details-marker { display: none; }

.content > details.toggle {
  margin-bottom: 50px;
}