:root {
  --bg: #eef3f8;
  --ink: #1a2332;
  --muted: #5a6a7e;
  --dim: #7b8898;
  --line: #c5d2e0;
  --accent: #2b5ea7;
  --accent-dim: #1e447c;
  --paper: #f7fafc;
  --good: #1f6b4a;
  --bad: #a33a32;
  --warn: #8a5a12;
  --sans: "PingFang SC", "Hiragino Sans GB", "Noto Sans SC", ui-sans-serif, system-ui, sans-serif;
  --serif: "Songti SC", "STSong", "Noto Serif CJK SC", "Source Han Serif SC", Georgia, serif;
  --mono: "SFMono-Regular", ui-monospace, Menlo, Consolas, monospace;
  --page: min(44rem, calc(100vw - 2.4rem));
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  color: var(--ink);
  background-color: var(--bg);
  background-image:
    linear-gradient(rgba(43, 94, 167, 0.07) 1px, transparent 1px),
    linear-gradient(90deg, rgba(43, 94, 167, 0.07) 1px, transparent 1px);
  background-size: 28px 28px;
  background-attachment: fixed;
  font: 16.5px/1.75 var(--sans);
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}
button, input, textarea, select { font: inherit; color: inherit; }
a { color: var(--accent); text-underline-offset: 0.18em; }
a:hover { color: var(--accent-dim); }
a:focus-visible,
button:focus-visible,
input:focus-visible,
textarea:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
}
code, .shape, .mono { font-family: var(--mono); font-size: 0.92em; }

.skip {
  position: absolute;
  left: 12px;
  top: 12px;
  z-index: 20;
  padding: 8px 12px;
  background: var(--accent);
  color: #fff;
  transform: translateY(-160%);
}
.skip:focus { transform: none; }

.top {
  position: sticky;
  top: 0;
  z-index: 10;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 10px 18px;
  padding: 10px 4vw;
  background: color-mix(in srgb, var(--bg) 92%, white);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(10px);
}
.brand {
  font: 700 15px/1 var(--serif);
  color: var(--ink);
  text-decoration: none;
  letter-spacing: 0.02em;
}
.brand:hover { color: var(--accent); }
.sits {
  display: flex;
  flex-wrap: wrap;
  gap: 4px 2px;
  flex: 1;
}
.sits a {
  padding: 4px 8px;
  color: var(--muted);
  text-decoration: none;
  font: 700 12px/1.3 var(--mono);
  letter-spacing: 0.02em;
}
.sits a:hover,
.sits a.is-here { color: var(--accent); }
.sits a.is-here { box-shadow: inset 0 -2px 0 var(--accent); }
.out {
  display: flex;
  gap: 14px;
  margin-left: auto;
  font-size: 13px;
}
.out a { color: var(--muted); text-decoration: none; }
.out a:hover { color: var(--ink); }

main { width: var(--page); margin: 0 auto; padding: 2.8rem 0 4.5rem; }

.kicker {
  margin: 0 0 10px;
  color: var(--accent);
  font: 700 11px/1.4 var(--mono);
  letter-spacing: 0.12em;
}
h1 {
  margin: 0 0 16px;
  font: 700 clamp(28px, 5vw, 42px)/1.2 var(--serif);
  letter-spacing: -0.02em;
}
h2 {
  margin: 2.2rem 0 0.7rem;
  font: 700 1.35rem/1.35 var(--serif);
}
h3 {
  margin: 1.4rem 0 0.45rem;
  font: 700 1.05rem/1.4 var(--serif);
}
.lede { margin: 0 0 1.2rem; color: var(--muted); font-size: 17px; }
p { margin: 0 0 1rem; }
ul, ol { margin: 0 0 1.1rem; padding-left: 1.2rem; }
li { margin: 0.28rem 0; }
li + li { margin-top: 0.45rem; }

.hero { margin-bottom: 2.2rem; }
.hero-links { display: flex; flex-wrap: wrap; gap: 14px 22px; margin-top: 1.2rem; }

.cards {
  display: grid;
  gap: 12px;
  margin: 1.6rem 0 2.4rem;
}
.card {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 10px 16px;
  padding: 16px 18px;
  background: var(--paper);
  border: 1px solid var(--line);
  text-decoration: none;
  color: inherit;
  box-shadow: 2px 2px 0 rgba(43, 94, 167, 0.06);
}
.card:hover { border-color: var(--accent); }
.card .n {
  font: 700 13px/1 var(--mono);
  color: var(--accent);
}
.card b { font: 700 18px/1.3 var(--serif); }
.card span { color: var(--muted); font-size: 14px; line-height: 1.55; }

.panel {
  background: var(--paper);
  border: 1px solid var(--line);
  padding: 1.1rem 1.2rem 1.2rem;
  margin: 1.2rem 0 1.6rem;
}
.panel h2 { margin-top: 0; }
.ledger {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--mono);
  font-size: 13.5px;
  margin: 0.8rem 0 1.1rem;
}
.ledger th, .ledger td {
  border-bottom: 1px solid var(--line);
  text-align: left;
  padding: 0.4rem 0.55rem 0.4rem 0;
}
.ledger th { color: var(--muted); font-weight: 600; }
.note {
  border-left: 3px solid var(--accent);
  padding: 0.15rem 0 0.15rem 0.9rem;
  color: var(--muted);
}
.warn {
  border-left: 3px solid var(--bad);
  padding: 0.15rem 0 0.15rem 0.9rem;
}

.work {
  margin: 1.6rem 0 2rem;
  padding: 1.15rem 1.2rem 1.3rem;
  background: #fff;
  border: 1px solid var(--accent);
}
.work h2 { margin-top: 0; color: var(--accent-dim); }
.work .hint { color: var(--muted); font-size: 14px; }

label.field {
  display: grid;
  gap: 6px;
  margin: 0 0 12px;
  font-size: 14px;
  color: var(--muted);
}
input[type="text"], textarea {
  width: 100%;
  border: 1px solid var(--line);
  background: #fff;
  padding: 8px 10px;
  border-radius: 0;
}
.actions { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 10px; }
button {
  min-height: 40px;
  padding: 0 14px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: #fff;
  cursor: pointer;
}
button.ghost, .choices button {
  background: #fff;
  color: var(--ink);
  border-color: var(--line);
}
button:hover { filter: brightness(1.05); }
.choices {
  display: grid;
  gap: 8px;
  margin: 10px 0;
}
.choices button { text-align: left; padding: 10px 12px; min-height: 44px; }
.choices button[aria-pressed="true"] {
  border-color: var(--accent);
  box-shadow: inset 3px 0 0 var(--accent);
}
.choices button.is-right { border-color: var(--good); box-shadow: inset 3px 0 0 var(--good); }
.choices button.is-wrong { border-color: var(--bad); box-shadow: inset 3px 0 0 var(--bad); }
.outbox {
  min-height: 1.5em;
  margin: 0.6rem 0 0;
  font-size: 15px;
}
.outbox.ok { color: var(--good); }
.outbox.bad { color: var(--bad); }
.saved { color: var(--good); font-size: 14px; }

.grid3 {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
}
.curve {
  padding: 10px;
  border: 1px solid var(--line);
  background: #fff;
  cursor: pointer;
  text-align: left;
}
.curve[aria-pressed="true"] { border-color: var(--accent); }
.curve svg { display: block; width: 100%; height: 88px; }
.curve b { display: block; margin-top: 6px; font: 700 13px/1.3 var(--mono); }
.curve span { color: var(--muted); font-size: 12px; }

.attn {
  display: grid;
  grid-template-columns: auto repeat(3, 1fr);
  gap: 6px;
  max-width: 22rem;
  font-family: var(--mono);
  font-size: 13px;
  margin: 12px 0;
}
.attn span.head, .attn .lab { color: var(--muted); padding: 6px; }
.attn button {
  background: #fff;
  color: var(--ink);
  border: 1px solid var(--line);
  min-height: 48px;
}
.attn button.masked {
  background: #1a2332;
  color: #dce6f2;
  border-color: #1a2332;
}
.attn button.self { box-shadow: inset 0 0 0 2px var(--accent); }

.check-list label {
  display: flex;
  gap: 10px;
  align-items: flex-start;
  margin: 0 0 8px;
  font-size: 15px;
}
details {
  margin: 1rem 0;
  border: 1px dashed var(--line);
  padding: 0.6rem 0.85rem;
  background: color-mix(in srgb, var(--paper) 80%, transparent);
}
details summary { cursor: pointer; color: var(--accent-dim); font-weight: 600; }
details p:last-child { margin-bottom: 0; }

.nodes {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 12px 0;
}
.node {
  min-width: 4.6rem;
  padding: 8px 10px;
  background: #fff;
  border: 1px solid var(--line);
  font-family: var(--mono);
  font-size: 13px;
  text-align: center;
}
.node b { display: block; color: var(--accent); font-size: 16px; }

.foot {
  width: var(--page);
  margin: 0 auto;
  padding: 1.2rem 0 2.4rem;
  border-top: 1px solid var(--line);
  display: flex;
  flex-wrap: wrap;
  justify-content: space-between;
  gap: 10px;
  color: var(--muted);
  font-size: 14px;
}
.foot a { color: var(--muted); }
.foot a:hover { color: var(--ink); }

@media (max-width: 720px) {
  .grid3 { grid-template-columns: 1fr; }
  .top { position: static; }
  .sits { order: 3; width: 100%; }
}