:root {
  --bg: #ffffff;
  --panel: #ffffff;
  --line: #000000;
  --soft: #d9d9d9;
  --text: #000000;
  --dim: #555555;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Source Han Sans SC", "Noto Sans SC", "PingFang SC",
    "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  line-height: 1.9;
  font-size: 16.5px;
}

header.hero {
  padding: 72px 24px 44px;
  border-bottom: 1px solid var(--line);
}

.inner { max-width: 820px; margin: 0 auto; }

.hero h1 {
  font-size: 2.5rem;
  line-height: 1.35;
  margin: 0 0 12px;
  letter-spacing: 0.5px;
}

.hero .sub { color: var(--dim); margin: 0 0 6px; }
.hero .meta { color: var(--dim); font-size: 0.9rem; margin-top: 20px; }

main { padding: 8px 24px 96px; }

section { margin: 64px 0 0; }

h2 { font-size: 1.5rem; margin: 0 0 4px; padding-top: 8px; }

h2 .num {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  font-size: 0.95rem;
  margin-right: 10px;
  color: var(--dim);
}

p { margin: 16px 0; }
.lead { color: #000; }
strong { font-weight: 700; }

code {
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
  background: #f2f2f2;
  border: 1px solid var(--soft);
  border-radius: 8px;
  padding: 1px 6px;
  font-size: 0.88em;
}

figure {
  margin: 28px 0;
  background: var(--panel);
  border: 1px solid var(--line);
  border-radius: 8px;
  overflow: hidden;
}

figcaption {
  padding: 12px 16px;
  border-top: 1px solid var(--soft);
  color: var(--dim);
  font-size: 0.9rem;
  line-height: 1.7;
}

figcaption .name { color: #000; font-weight: 700; }
figcaption a { color: #000; text-decoration: underline; }

.lv-canvas {
  display: block;
  width: 100%;
  height: 300px;
  background: #ffffff;
}

.lv-bar {
  display: flex;
  flex-wrap: wrap;
  gap: 6px 14px;
  align-items: center;
  padding: 10px 12px;
  border-top: 1px solid var(--soft);
  background: #fafafa;
}

.lv-group { display: flex; flex-wrap: wrap; gap: 4px; }

.lv-btn {
  background: #ffffff;
  color: #000000;
  border: 1px solid var(--soft);
  border-radius: 8px;
  padding: 4px 10px;
  font-size: 0.82rem;
  font-family: inherit;
  cursor: pointer;
}
.lv-btn:hover { border-color: #000; }
.lv-btn.on { background: #000000; color: #ffffff; border-color: #000000; }

.lv-stat {
  margin-left: auto;
  color: var(--dim);
  font-size: 0.8rem;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
}

.tip {
  border-left: 2px solid #000;
  padding: 4px 0 4px 18px;
  color: var(--dim);
  margin: 24px 0;
}

footer {
  border-top: 1px solid var(--line);
  padding: 40px 24px 80px;
  color: var(--dim);
  font-size: 0.88rem;
}
footer a { color: #000; text-decoration: underline; }

nav.toc {
  margin: 40px 0 0;
  padding: 20px 24px;
  border: 1px solid var(--line);
  border-radius: 8px;
}
nav.toc div { color: var(--dim); font-size: 0.85rem; margin-bottom: 10px; }
nav.toc ol { margin: 0; padding-left: 22px; }
nav.toc li { margin: 3px 0; }
nav.toc a { color: #000; text-decoration: none; }
nav.toc a:hover { text-decoration: underline; }

@media (max-width: 640px) {
  .hero h1 { font-size: 1.8rem; }
  body { font-size: 15.5px; }
  .lv-canvas { height: 240px; }
}