:root {
  --indigo: #584cf4;
  --deep: #1c1b3a;
  --muted: #5b5a75;
  --canvas: #f4f4fb;
  --line: #e3e2f0;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Noto Sans",
    Roboto, sans-serif;
  color: var(--deep);
  background: #fff;
  line-height: 1.6;
  -webkit-text-size-adjust: 100%;
}

header {
  background: linear-gradient(140deg, #6d5ff7, #4a3fd6);
  color: #fff;
  padding: 28px 20px;
}

header .wrap { max-width: 760px; margin: 0 auto; }

header a.brand {
  color: #fff;
  text-decoration: none;
  font-weight: 800;
  font-size: 20px;
  letter-spacing: -0.3px;
}

header p {
  margin: 6px 0 0;
  font-size: 13.5px;
  color: rgba(255, 255, 255, 0.82);
}

nav {
  border-bottom: 1px solid var(--line);
  background: var(--canvas);
  padding: 12px 20px;
}

nav .wrap {
  max-width: 760px;
  margin: 0 auto;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 18px;
  font-size: 13.5px;
}

nav a { color: var(--muted); text-decoration: none; }
nav a:hover, nav a[aria-current="page"] { color: var(--indigo); font-weight: 600; }

main {
  max-width: 760px;
  margin: 0 auto;
  padding: 32px 20px 60px;
}

h1 { font-size: 26px; letter-spacing: -0.5px; margin: 0 0 6px; }
h2 { font-size: 17px; margin: 30px 0 8px; }
p, li { font-size: 15px; color: #2b2a4d; }
ul { padding-left: 22px; }
a { color: var(--indigo); }

.updated { color: var(--muted); font-size: 13px; margin: 0 0 26px; }

.card {
  border: 1px solid var(--line);
  border-radius: 14px;
  padding: 18px 20px;
  background: var(--canvas);
  margin: 22px 0;
}

.card p:first-child { margin-top: 0; }
.card p:last-child { margin-bottom: 0; }

dl { margin: 0; }
dt { font-weight: 700; font-size: 14px; margin-top: 12px; }
dd { margin: 2px 0 0; font-size: 15px; color: #2b2a4d; }

table { border-collapse: collapse; width: 100%; font-size: 14.5px; }
th, td { text-align: left; padding: 8px 10px; border-bottom: 1px solid var(--line); }

footer {
  border-top: 1px solid var(--line);
  padding: 24px 20px 40px;
  color: var(--muted);
  font-size: 13px;
}

footer .wrap { max-width: 760px; margin: 0 auto; }
footer a { color: var(--muted); }

/* ───────────────────────────────────────────────────────────────────────
   Generated pages (site/build.py). The tokens above already match the app's
   palette; these add the study surfaces — chapter reading, the practice
   engine, progress.

   Two things drive the choices here. Long-form reading on a phone, because
   these chapters run to 140 KB and are read in ten-minute sessions on a
   commute. And dense drill tables — ch11 alone has 658 table rows — which
   must scroll inside their own box rather than pushing the page sideways.
   ─────────────────────────────────────────────────────────────────────── */

:root {
  --amber: #f7b32b;
  --coral: #f25c54;
  --green: #1fa45b;
  --deep-app: #221c63;
}

header nav {
  border: 0; background: none; padding: 14px 0 0; margin: 0;
  display: flex; flex-wrap: wrap; gap: 6px 16px;
}
header nav a {
  color: rgba(255,255,255,0.78); font-size: 13.5px; font-weight: 600;
  text-decoration: none; padding: 2px 0; border-bottom: 2px solid transparent;
}
header nav a:hover { color: #fff; }
header nav a.on { color: #fff; border-bottom-color: rgba(255,255,255,0.9); }

main.wide { max-width: 100%; }
h1 { font-size: 30px; line-height: 1.18; }
.lede { font-size: 17px; line-height: 1.6; color: var(--muted); }
.muted { color: var(--muted); }
.small { font-size: 12.5px; }

/* Buttons ------------------------------------------------------------- */
.btn {
  display: inline-block; padding: 12px 20px; border-radius: 13px;
  background: var(--indigo); color: #fff; font-weight: 700; font-size: 14.5px;
  text-decoration: none; border: 0; cursor: pointer; font-family: inherit;
}
.btn:hover { filter: brightness(1.07); }
.btn.ghost { background: #fff; color: var(--indigo); border: 1px solid var(--line); }
.btn.ghost.danger { color: var(--coral); }
.btn[disabled] { opacity: 0.4; cursor: default; }
.cta-row { display: flex; flex-wrap: wrap; gap: 10px; margin: 24px 0; }

/* Tags ---------------------------------------------------------------- */
.tag {
  display: inline-block; font-size: 10.5px; font-weight: 800; letter-spacing: 0.7px;
  padding: 4px 9px; border-radius: 8px; background: var(--canvas);
  color: var(--deep-app); margin-bottom: 10px;
}
.tag.free { background: rgba(31,164,91,0.13); color: #14713e; }
.tag.pyq  { background: rgba(247,179,43,0.18); color: #7a5406; }

/* Stat rows ----------------------------------------------------------- */
.stats, .chapter-meta {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 12px; margin: 24px 0;
}
.stats div, .chapter-meta div {
  background: var(--canvas); border: 1px solid var(--line);
  border-radius: 14px; padding: 14px 16px;
}
.stats b, .chapter-meta b {
  display: block; font-size: 24px; letter-spacing: -0.6px; color: var(--deep-app);
}
.stats span, .chapter-meta span { font-size: 12.5px; color: var(--muted); }

/* Cards --------------------------------------------------------------- */
.grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(230px,1fr)); gap: 14px; }
a.card {
  display: block; text-decoration: none; color: inherit; margin: 0;
  background: #fff; transition: border-color .15s, transform .15s;
}
a.card:hover { border-color: var(--indigo); transform: translateY(-2px); }
a.card h3 { margin: 0 0 4px; font-size: 16px; letter-spacing: -0.2px; }
a.card p { margin: 0; font-size: 13px; color: var(--muted); }
.list a.card.wide {
  display: flex; align-items: center; justify-content: space-between;
  gap: 16px; margin-bottom: 12px;
}
.chev { font-size: 26px; color: var(--muted); line-height: 1; }
ul.cols { columns: 2; column-gap: 26px; padding-left: 20px; }
ul.cols li { font-size: 14px; break-inside: avoid; margin-bottom: 4px; }
@media (max-width: 560px) { ul.cols { columns: 1; } }

/* Chapter reading ------------------------------------------------------ */
.crumb { font-size: 13px; color: var(--muted); margin-bottom: 14px; }
.toc {
  background: var(--canvas); border: 1px solid var(--line);
  border-radius: 14px; padding: 14px 18px; margin: 26px 0;
}
.toc summary { font-weight: 700; cursor: pointer; font-size: 14.5px; }
.toc a { display: block; padding: 5px 0; font-size: 14px; text-decoration: none; }
.toc a:hover { text-decoration: underline; }
.toc b { color: var(--muted); font-weight: 700; font-size: 12px; }

section[id] { scroll-margin-top: 16px; padding-top: 8px; }
section .part {
  display: inline-block; font-size: 11px; font-weight: 800; letter-spacing: 1px;
  color: var(--indigo); margin-bottom: 2px;
}
section h2 { font-size: 22px; letter-spacing: -0.4px; margin: 2px 0 14px; }
section h3 { font-size: 16.5px; margin: 24px 0 6px; }
section h4 { font-size: 15px; margin: 18px 0 4px; }
.part-sheet {
  background: var(--canvas); border: 1px solid var(--line);
  border-radius: 16px; padding: 20px; margin-top: 30px;
}

/* Trap callouts and every other blockquote in the source. */
blockquote {
  margin: 16px 0; padding: 12px 16px; border-left: 3px solid var(--amber);
  background: rgba(247,179,43,0.09); border-radius: 0 12px 12px 0;
}
blockquote p { margin: 0 0 6px; font-size: 14.5px; }
blockquote p:last-child { margin-bottom: 0; }

pre {
  background: var(--deep-app); color: #eae8ff; padding: 14px 16px;
  border-radius: 12px; overflow-x: auto; font-size: 13px; line-height: 1.55;
}
code { font-size: 13.5px; }
:not(pre) > code {
  background: var(--canvas); padding: 1px 5px; border-radius: 5px;
  border: 1px solid var(--line);
}

/* Wide drill tables scroll inside their own box. */
.tw { overflow-x: auto; margin: 16px 0; -webkit-overflow-scrolling: touch; }
.tw table { min-width: 100%; font-size: 14px; }
.tw th {
  background: var(--canvas); font-size: 12.5px; letter-spacing: 0.2px;
  position: sticky; top: 0;
}
.tw td, .tw th { vertical-align: top; }

.note {
  background: var(--canvas); border: 1px solid var(--line);
  border-radius: 12px; padding: 12px 16px; font-size: 14px;
}
.note.star { border-color: rgba(247,179,43,0.5); background: rgba(247,179,43,0.08); }
.note.good { border-color: rgba(31,164,91,0.4); background: rgba(31,164,91,0.08); }
.note.bad  { border-color: rgba(242,92,84,0.4); background: rgba(242,92,84,0.08); }

.endcap {
  margin-top: 44px; padding: 24px; border-radius: 16px;
  background: linear-gradient(140deg, #6d5ff7, #4a3fd6); color: #fff;
}
.endcap h2 { color: #fff; margin-top: 0; }
.endcap p { color: rgba(255,255,255,0.88); }
.endcap .btn { background: #fff; color: var(--indigo); }

/* Practice ------------------------------------------------------------- */
.pick { display: block; font-size: 13px; color: var(--muted); margin: 22px 0 8px; }
.pick select {
  display: block; margin-top: 6px; width: 100%; padding: 11px 12px;
  border: 1px solid var(--line); border-radius: 12px; font-size: 15px;
  font-family: inherit; color: var(--deep-app); background: #fff;
}
.qbar {
  display: flex; justify-content: space-between; align-items: center;
  font-size: 13px; color: var(--muted); margin: 22px 0 10px; font-weight: 600;
}
.qbar .sc { font-variant-numeric: tabular-nums; color: var(--deep-app); }
.qcard {
  border: 1px solid var(--line); border-radius: 18px; padding: 20px;
  background: #fff;
}
.stem { font-size: 16px; line-height: 1.6; }
.stem p:first-child { margin-top: 0; }
.stem table { font-size: 14px; }
.opts { display: grid; gap: 9px; margin: 18px 0 6px; }
.opt {
  display: flex; gap: 11px; align-items: flex-start; text-align: left;
  width: 100%; padding: 13px 15px; border: 1px solid var(--line);
  border-radius: 13px; background: #fff; cursor: pointer; font-family: inherit;
  font-size: 15px; color: var(--deep-app); line-height: 1.5;
}
.opt:hover:not([disabled]) { border-color: var(--indigo); background: var(--canvas); }
.opt .k {
  flex: 0 0 24px; height: 24px; border-radius: 7px; background: var(--canvas);
  font-weight: 800; font-size: 12px; display: grid; place-items: center;
  text-transform: lowercase;
}
.opt .t p { margin: 0; font-size: 15px; }
.opt.right { border-color: var(--green); background: rgba(31,164,91,0.08); }
.opt.right .k { background: var(--green); color: #fff; }
.opt.wrong { border-color: var(--coral); background: rgba(242,92,84,0.08); }
.opt.wrong .k { background: var(--coral); color: #fff; }
.opt[disabled] { cursor: default; }
.blank {
  width: 100%; padding: 11px; border: 1px dashed var(--line); border-radius: 12px;
  background: none; color: var(--muted); font-family: inherit; font-size: 13.5px;
  cursor: pointer;
}
.blank:hover { border-color: var(--indigo); color: var(--indigo); }
.expl {
  margin-top: 16px; padding: 15px 17px; border-radius: 13px;
  background: var(--canvas); font-size: 14.5px; line-height: 1.6;
}
.expl b { display: block; margin-bottom: 6px; }
.expl p { margin: 0 0 8px; font-size: 14.5px; }
.expl p:last-child { margin-bottom: 0; }
/* Distractor analysis travels in *asterisks* and reads as an aside. */
.expl em { color: var(--muted); font-style: italic; }
.arhelp {
  margin: 14px 0 0; padding: 11px 14px; border-radius: 11px;
  background: rgba(88,76,244,0.07); font-size: 13px;
}
.arhelp b { font-size: 12px; letter-spacing: 0.3px; }
.arhelp p { margin: 4px 0 0; font-size: 13px; color: var(--muted); }
.nav { display: flex; gap: 10px; margin: 16px 0 0; }
.nav .btn { flex: 1; text-align: center; }
.tally {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(100px,1fr));
  gap: 10px; margin-top: 20px;
}
.tally div { background: var(--canvas); border-radius: 12px; padding: 11px 13px; }
.tally b { display: block; font-size: 19px; color: var(--deep-app); }
.tally span { font-size: 11.5px; color: var(--muted); }

/* Progress ------------------------------------------------------------- */
.bar { background: var(--canvas); border-radius: 99px; height: 7px; min-width: 70px; }
.bar i { display: block; height: 7px; border-radius: 99px; background: var(--indigo); }

/* Plan ----------------------------------------------------------------- */
.price { margin: 22px 0 8px; }
.price b { font-size: 40px; letter-spacing: -1.5px; color: var(--deep-app); }
.price span { font-size: 15px; color: var(--muted); margin-left: 8px; }
ul.ticks { list-style: none; padding: 0; margin: 18px 0; }
ul.ticks li { padding: 8px 0 8px 28px; position: relative; font-size: 15px; }
ul.ticks li::before {
  content: "✓"; position: absolute; left: 0; color: var(--green); font-weight: 800;
}

@media (max-width: 560px) {
  h1 { font-size: 25px; }
  .stats b, .chapter-meta b { font-size: 20px; }
  .price b { font-size: 33px; }
}

/* The chapter's syllabus-head line. Small and grey: it is orientation, not
   a headline — the title above it is the headline. */
p.meta { font-size: 13.5px; color: var(--muted); margin: 2px 0 18px; }