/* Base Case — hand-written stylesheet, no framework. */

:root {
  --bg:        #f7f8fa;
  --surface:   #ffffff;
  --ink:       #1b1f24;
  --ink-muted: #616b76;
  --rule:      #dfe3e8;
  --rule-soft: #eaedf1;
  --accent:    #0f6b62;
  --accent-dim:#0b524b;
  --mark:      #eef1f4;
  --measure:   42rem;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", "Cascadia Mono", Menlo, Consolas, "Liberation Mono", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg:        #14171a;
    --surface:   #1b1f23;
    --ink:       #e4e8ec;
    --ink-muted: #939ca6;
    --rule:      #2b3137;
    --rule-soft: #23282d;
    --accent:    #52c4b4;
    --accent-dim:#3ea294;
    --mark:      #23282d;
  }
}

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

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
}

.wrap {
  max-width: var(--measure);
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ---- masthead ---------------------------------------------------------- */

header.masthead {
  border-bottom: 1px solid var(--rule);
  background: var(--surface);
  padding: 1.15rem 0;
  margin-bottom: 3rem;
}

header.masthead .wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: .7rem 1.4rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: .55rem;
  text-decoration: none;
  color: inherit;
}

.brand svg { flex: none; }

.brand b {
  font-family: var(--mono);
  font-weight: 600;
  font-size: .98rem;
  letter-spacing: -.02em;
}

.brand span {
  font-size: .76rem;
  color: var(--ink-muted);
}

nav {
  font-size: .82rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0 1rem;
}

nav a {
  color: var(--ink-muted);
  text-decoration: none;
  padding-bottom: 2px;
  border-bottom: 1.5px solid transparent;
}

nav a:hover { color: var(--ink); border-bottom-color: var(--accent); }
nav a[aria-current="page"] { color: var(--ink); border-bottom-color: var(--accent); }

/* ---- prose ------------------------------------------------------------- */

h1 {
  font-size: 1.95rem;
  line-height: 1.2;
  font-weight: 650;
  letter-spacing: -.022em;
  margin: 0 0 .5rem;
}

.standfirst {
  color: var(--ink-muted);
  font-size: 1.05rem;
  line-height: 1.55;
  margin: 0 0 2.4rem;
  max-width: 34rem;
}

h2 {
  font-size: 1.2rem;
  font-weight: 650;
  letter-spacing: -.012em;
  margin: 2.8rem 0 .8rem;
  padding-top: 1.4rem;
  border-top: 1px solid var(--rule-soft);
}

h3 {
  font-size: 1rem;
  font-weight: 650;
  letter-spacing: -.008em;
  margin: 1.9rem 0 .5rem;
}

.kicker {
  font-family: var(--mono);
  font-size: .72rem;
  font-weight: 600;
  letter-spacing: .08em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 .5rem;
}

p { margin: 0 0 1.1rem; }

a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent-dim); }

ul, ol { margin: 0 0 1.1rem; padding-left: 1.25rem; }
li { margin-bottom: .5rem; }
li > ul, li > ol { margin-top: .5rem; }

strong { font-weight: 650; }

code, .mono {
  font-family: var(--mono);
  font-size: .86em;
  background: var(--mark);
  padding: .1em .34em;
  border-radius: 3px;
}

/* ---- callout ----------------------------------------------------------- */

.note {
  margin: 1.8rem 0;
  padding: .95rem 1.15rem;
  background: var(--surface);
  border: 1px solid var(--rule);
  border-left: 3px solid var(--accent);
  border-radius: 0 5px 5px 0;
  font-size: .95rem;
}

.note p:last-child { margin-bottom: 0; }

/* ---- stage list -------------------------------------------------------- */

.stages { margin: 1.8rem 0; }

.stage {
  padding: 1.1rem 0;
  border-top: 1px solid var(--rule-soft);
  display: grid;
  grid-template-columns: 8.5rem 1fr;
  gap: 0 1.4rem;
}

.stage:last-child { border-bottom: 1px solid var(--rule-soft); }

.stage .label {
  font-family: var(--mono);
  font-size: .78rem;
  font-weight: 600;
  color: var(--ink-muted);
  padding-top: .18rem;
  letter-spacing: -.01em;
}

.stage .body p { margin: 0 0 .6rem; }
.stage .body p:last-child { margin-bottom: 0; }

/* ---- tables ------------------------------------------------------------ */

.table-scroll { overflow-x: auto; margin: 1.7rem 0; }

table {
  border-collapse: collapse;
  width: 100%;
  font-size: .92rem;
}

th, td {
  text-align: left;
  padding: .55rem .8rem .55rem 0;
  border-bottom: 1px solid var(--rule-soft);
  vertical-align: top;
}

thead th { border-bottom: 1px solid var(--rule); }

th {
  font-family: var(--mono);
  font-size: .72rem;
  font-weight: 600;
  letter-spacing: .06em;
  text-transform: uppercase;
  color: var(--ink-muted);
  white-space: nowrap;
}

td.term { font-weight: 600; }
td.num  { font-family: var(--mono); font-size: .86rem; white-space: nowrap; }

/* ---- index cards ------------------------------------------------------- */

.cards {
  margin: 2.6rem 0 0;
  display: grid;
  gap: .9rem;
}

.card {
  background: var(--surface);
  border: 1px solid var(--rule);
  border-radius: 6px;
  padding: 1.05rem 1.2rem;
}

.card .kicker { margin-bottom: .35rem; }

.card a {
  font-size: 1.06rem;
  font-weight: 650;
  letter-spacing: -.012em;
  text-decoration: none;
  color: var(--ink);
}

.card a:hover { color: var(--accent); }

.card p {
  margin: .35rem 0 0;
  color: var(--ink-muted);
  font-size: .93rem;
  line-height: 1.55;
}

/* ---- figures ----------------------------------------------------------- */

figure { margin: 2rem 0; }
figure svg { display: block; width: 100%; height: auto; }

figcaption {
  font-size: .8rem;
  color: var(--ink-muted);
  margin-top: .6rem;
  line-height: 1.5;
}

/* ---- footer ------------------------------------------------------------ */

footer {
  margin-top: 4.5rem;
  padding: 1.5rem 0 3.5rem;
  border-top: 1px solid var(--rule);
  font-size: .8rem;
  color: var(--ink-muted);
}

footer .wrap {
  display: flex;
  flex-wrap: wrap;
  gap: .4rem 1.2rem;
  justify-content: space-between;
}

footer a { color: var(--ink-muted); }
footer a:hover { color: var(--accent); }

/* ---- small screens ----------------------------------------------------- */

@media (max-width: 34rem) {
  body { font-size: 16px; }
  h1 { font-size: 1.6rem; }
  header.masthead .wrap { display: block; }
  nav { margin-top: .8rem; gap: 0 .9rem; }
  .stage { grid-template-columns: 1fr; gap: .3rem; }
  .stage .label { padding-top: 0; }
}