/* Self-hosted fonts (SIL Open Font License; see vendor/fonts/LICENSE-*). */
@font-face { font-family: "Inter"; font-style: normal; font-weight: 400; font-display: swap; src: url("vendor/fonts/inter-latin-400-normal.woff2") format("woff2"); }
@font-face { font-family: "Inter"; font-style: normal; font-weight: 500; font-display: swap; src: url("vendor/fonts/inter-latin-500-normal.woff2") format("woff2"); }
@font-face { font-family: "Inter"; font-style: normal; font-weight: 600; font-display: swap; src: url("vendor/fonts/inter-latin-600-normal.woff2") format("woff2"); }
@font-face { font-family: "Newsreader"; font-style: normal; font-weight: 500; font-display: swap; src: url("vendor/fonts/newsreader-latin-500-normal.woff2") format("woff2"); }
@font-face { font-family: "Newsreader"; font-style: normal; font-weight: 600; font-display: swap; src: url("vendor/fonts/newsreader-latin-600-normal.woff2") format("woff2"); }
/* Calc Practice — one stylesheet for every page. */
:root {
  --paper: #fbfaf6;
  --card: #ffffff;
  --ink: #1b1c20;
  --ink-2: #3c3e46;
  --muted: #6d6f78;
  --line: #e6e2d8;
  --line-2: #efece4;
  --accent: #1d4f91;
  --accent-soft: #e8eef8;
  --proved: #1f7a4d;
  --proved-soft: #e6f3ec;
  --numeric: #9a6a10;
  --numeric-soft: #fbf1dc;
  --reviewed: #4a4fa3;
  --reviewed-soft: #ecedf8;
  --fail: #a4282c;
  --shadow: 0 1px 2px rgba(20, 20, 30, .04), 0 6px 24px rgba(20, 20, 30, .05);
  --radius: 14px;
  --serif: "Newsreader", "Iowan Old Style", "Palatino Linotype", Georgia, serif;
  --sans: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --paper: #131418; --card: #1b1c22; --ink: #ecebe6; --ink-2: #c9c8c2; --muted: #9a9ba3;
    --line: #2c2e36; --line-2: #24262d; --accent: #8db4ff; --accent-soft: #1d2638;
    --proved: #6fd09c; --proved-soft: #183126; --numeric: #e3b25a; --numeric-soft: #33291a;
    --reviewed: #a9adff; --reviewed-soft: #25263d; --fail: #ff8a8a;
    --shadow: 0 1px 2px rgba(0, 0, 0, .3), 0 8px 28px rgba(0, 0, 0, .25);
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --paper: #131418; --card: #1b1c22; --ink: #ecebe6; --ink-2: #c9c8c2; --muted: #9a9ba3;
  --line: #2c2e36; --line-2: #24262d; --accent: #8db4ff; --accent-soft: #1d2638;
  --proved: #6fd09c; --proved-soft: #183126; --numeric: #e3b25a; --numeric-soft: #33291a;
  --reviewed: #a9adff; --reviewed-soft: #25263d; --fail: #ff8a8a;
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0; background: var(--paper); color: var(--ink);
  font: 16px/1.6 var(--sans); font-feature-settings: "cv11", "ss01";
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }
img { max-width: 100%; }
.wrap { max-width: 780px; margin: 0 auto; padding: 0 16px; }
.wide { max-width: 1120px; margin: 0 auto; padding: 0 16px; }

/* ---- header ---- */
.top { position: sticky; top: 0; z-index: 20; background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(1.4) blur(10px); -webkit-backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--line); }
.bar { max-width: 1120px; margin: 0 auto; padding: 10px 16px; display: flex; align-items: center; gap: 18px; }
.brand { display: flex; align-items: center; gap: 9px; color: var(--ink); font: 600 1.18rem/1 var(--serif);
  letter-spacing: -.01em; white-space: nowrap; }
.brand:hover { text-decoration: none; }
.mark { display: inline-grid; place-items: center; width: 30px; height: 30px; border-radius: 9px;
  background: var(--ink); color: var(--paper); font: 500 1.15rem/1 var(--serif); }
.nav { display: flex; gap: 16px; font-size: .92rem; }
.nav a { color: var(--ink-2); }
.search { position: relative; margin-left: auto; flex: 0 1 340px; }
.search input { width: 100%; font: inherit; font-size: .93rem; padding: 8px 12px 8px 34px; border-radius: 10px;
  border: 1px solid var(--line); background: var(--card); color: var(--ink); outline: none; }
.search input:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.search svg { position: absolute; left: 11px; top: 50%; transform: translateY(-50%); color: var(--muted); }
.results { position: absolute; right: 0; left: 0; top: calc(100% + 6px); background: var(--card);
  border: 1px solid var(--line); border-radius: 12px; box-shadow: var(--shadow); padding: 6px; display: none;
  max-height: 70vh; overflow: auto; }
.results.open { display: block; }
.results a { display: block; padding: 8px 10px; border-radius: 8px; color: var(--ink); }
.results a:hover, .results a.on { background: var(--accent-soft); text-decoration: none; }
.results .rt { font-size: .92rem; }
.results .rs { font-size: .78rem; color: var(--muted); }
.results .none { padding: 10px; color: var(--muted); font-size: .9rem; }
@media (max-width: 760px) {
  .nav { display: none; }
  .bar { gap: 10px; }
  .search { flex: 1 1 auto; }
  .brand span.word { display: none; }
}

/* ---- type ---- */
h1, h2, h3 { font-family: var(--serif); font-weight: 600; letter-spacing: -.012em; line-height: 1.2; }
h1 { font-size: clamp(1.8rem, 1.2rem + 2.2vw, 2.5rem); margin: 0 0 10px; }
h2 { font-size: 1.45rem; margin: 44px 0 14px; }
h3 { font-size: 1.12rem; margin: 0 0 6px; }
.lead { font-size: 1.1rem; color: var(--ink-2); margin: 0 0 22px; max-width: 62ch; }
.muted { color: var(--muted); }
.small { font-size: .86rem; }
.crumbs { font-size: .85rem; color: var(--muted); margin: 26px 0 14px; }
.crumbs a { color: var(--muted); }
.crumbs span { margin: 0 6px; opacity: .6; }
main { padding-bottom: 80px; min-height: 70vh; }

/* ---- hero ---- */
.hero { padding: 64px 0 34px; text-align: left; }
.hero h1 { font-size: clamp(2.3rem, 1.4rem + 3.6vw, 3.6rem); max-width: 16ch; }
.hero .lead { font-size: 1.2rem; }
.bigsearch { position: relative; max-width: 620px; margin: 26px 0 12px; }
.bigsearch input { width: 100%; font: inherit; font-size: 1.06rem; padding: 15px 16px 15px 46px; border-radius: 14px;
  border: 1px solid var(--line); background: var(--card); color: var(--ink); box-shadow: var(--shadow); outline: none; }
.bigsearch input:focus { border-color: var(--accent); box-shadow: 0 0 0 4px var(--accent-soft), var(--shadow); }
.bigsearch svg { position: absolute; left: 16px; top: 50%; transform: translateY(-50%); color: var(--muted); }
.try { font-size: .88rem; color: var(--muted); }
.try a { margin-right: 10px; }
.stats { display: flex; flex-wrap: wrap; gap: 28px; margin: 30px 0 0; }
.stat b { display: block; font: 600 1.7rem/1.1 var(--serif); }
.stat span { font-size: .85rem; color: var(--muted); }

/* ---- cards and grids ---- */
.card { background: var(--card); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); }
.grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
@media (max-width: 900px) { .grid3 { grid-template-columns: 1fr; } }
.course { padding: 22px 22px 18px; }
.course h3 { font-size: 1.35rem; margin-bottom: 4px; }
.course h3 a { color: var(--ink); }
.course p { margin: 0 0 14px; color: var(--muted); font-size: .92rem; }
.course ul { list-style: none; margin: 0; padding: 0; columns: 1; }
.course li { padding: 5px 0; border-top: 1px solid var(--line-2); font-size: .93rem; display: flex; justify-content: space-between; gap: 10px; }
.course li .n { color: var(--muted); font-variant-numeric: tabular-nums; font-size: .82rem; }
.course .more { display: inline-block; margin-top: 12px; font-size: .9rem; }

.trust { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
@media (max-width: 900px) { .trust { grid-template-columns: 1fr; } }
.trust .card { padding: 20px 22px; }
.trust p { margin: 6px 0 0; color: var(--ink-2); font-size: .95rem; }

.chapter { margin: 34px 0 0; }
.chapter h2 { margin: 0 0 12px; font-size: 1.25rem; }
.topics { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px; }
@media (max-width: 700px) { .topics { grid-template-columns: 1fr; } }
.topic { padding: 16px 18px; display: block; color: var(--ink); transition: transform .12s ease, border-color .12s ease; }
.topic:hover { text-decoration: none; border-color: var(--accent); transform: translateY(-1px); }
.topic h3 { font-size: 1.05rem; }
.topic p { margin: 0; font-size: .88rem; color: var(--muted); }
.topic .n { font-size: .8rem; color: var(--accent); margin-top: 8px; display: block; }
.topic.empty { opacity: .55; }

/* ---- problem list ---- */
.filters { display: flex; flex-wrap: wrap; gap: 8px; margin: 6px 0 18px; }
.chip { font: inherit; font-size: .85rem; padding: 5px 12px; border-radius: 99px; border: 1px solid var(--line);
  background: var(--card); color: var(--ink-2); cursor: pointer; }
.chip.on { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.plist { display: grid; gap: 12px; }
.pcard { padding: 16px 18px; display: block; color: var(--ink); }
.pcard:hover { text-decoration: none; border-color: var(--accent); }
.pcard .st { font-size: 1.02rem; overflow-x: auto; }
.meta { display: flex; flex-wrap: wrap; align-items: center; gap: 8px 12px; font-size: .8rem; color: var(--muted); margin-top: 8px; }

/* ---- pills ---- */
.pill { display: inline-flex; align-items: center; gap: 5px; font-size: .74rem; font-weight: 500; line-height: 1;
  padding: 4px 9px; border-radius: 99px; white-space: nowrap; }
.p-proved, .p-independent { color: var(--proved); background: var(--proved-soft); }
.p-numeric { color: var(--numeric); background: var(--numeric-soft); }
.p-reviewed { color: var(--reviewed); background: var(--reviewed-soft); }
.p-not_checked { color: var(--muted); background: var(--line-2); }
.p-failed { color: var(--fail); background: var(--line-2); }
.p-badge { color: var(--accent); background: var(--accent-soft); }
.p-diff { color: var(--ink-2); background: var(--line-2); }

/* ---- a problem ---- */
.ptitle { margin-bottom: 4px; }
.pnum { font-size: .9rem; color: var(--muted); margin: 0 0 18px; }
.statement { padding: 24px 24px; font-size: 1.14rem; line-height: 1.7; overflow-x: auto; }
.statement .katex-display { margin: .4em 0; }
.controls { display: flex; flex-wrap: wrap; gap: 10px; margin: 22px 0 8px; }
.btn { font: inherit; font-size: .93rem; font-weight: 500; padding: 9px 16px; border-radius: 10px; cursor: pointer;
  border: 1px solid var(--line); background: var(--card); color: var(--ink); }
.btn.primary { background: var(--ink); color: var(--paper); border-color: var(--ink); }
.btn:hover { border-color: var(--accent); }
.btn[disabled] { opacity: .45; cursor: default; }
ol.steps { list-style: none; counter-reset: s; padding: 0; margin: 18px 0 0; }
ol.steps > li { counter-increment: s; position: relative; padding: 14px 0 14px 46px; border-top: 1px solid var(--line-2); }
ol.steps > li::before { content: counter(s); position: absolute; left: 0; top: 15px; width: 28px; height: 28px;
  border-radius: 50%; display: grid; place-items: center; font-size: .8rem; font-weight: 600; color: var(--muted);
  background: var(--line-2); }
.stepmath { overflow-x: auto; padding: 2px 0; font-size: 1.05rem; }
.steptext { color: var(--ink); }
.stepnote { color: var(--muted); font-size: .9rem; margin-top: 4px; display: flex; flex-wrap: wrap; gap: 6px 10px; align-items: center; }
.rule { font-family: var(--mono); font-size: .76rem; color: var(--ink-2); background: var(--line-2); padding: 1px 6px; border-radius: 5px; }
.js ol.steps > li.hidden { display: none; }
.answer { margin-top: 18px; padding: 18px 20px; border-left: 4px solid var(--proved); background: var(--proved-soft);
  border-radius: 0 12px 12px 0; overflow-x: auto; }
.answer b { font-family: var(--serif); font-size: 1.05rem; margin-right: 8px; }
.js .answer.hidden { display: none; }
.domain { margin-top: 14px; padding: 12px 16px; border-left: 4px solid var(--numeric); background: var(--numeric-soft);
  border-radius: 0 12px 12px 0; font-size: .93rem; }
.checked { margin-top: 26px; padding: 16px 18px; }
.checked p { margin: 0; font-size: .95rem; color: var(--ink-2); }
details.receipt { margin-top: 14px; }
details.receipt > summary { cursor: pointer; color: var(--accent); font-size: .92rem; list-style: none; }
details.receipt > summary::-webkit-details-marker { display: none; }
details.receipt > summary::before { content: "▸ "; }
details.receipt[open] > summary::before { content: "▾ "; }
.rtable { width: 100%; border-collapse: collapse; font-size: .84rem; margin: 12px 0; }
.rtable th, .rtable td { text-align: left; padding: 8px 8px; border-bottom: 1px solid var(--line-2); vertical-align: top; }
.rtable th { color: var(--muted); font-weight: 500; }
.rwrap { overflow-x: auto; }
.by { color: var(--muted); font-size: .8rem; }
.reviews { font-size: .88rem; }
.reviews li { margin: 6px 0; }
code { font-family: var(--mono); font-size: .84em; background: var(--line-2); padding: 1px 5px; border-radius: 5px; }
.fine { font-size: .8rem; color: var(--muted); line-height: 1.55; }
.pager { display: flex; justify-content: space-between; gap: 12px; margin-top: 34px; font-size: .92rem; }
.related { margin-top: 10px; }

/* ---- prose pages ---- */
.prose p, .prose li { color: var(--ink-2); font-size: 1.02rem; }
.prose h2 { font-size: 1.3rem; }
.labels { display: grid; gap: 10px; margin: 14px 0; }
.labels div { display: grid; grid-template-columns: 210px 1fr; gap: 12px; align-items: start; }
@media (max-width: 600px) { .labels div { grid-template-columns: 1fr; } }

table.cov { width: 100%; border-collapse: collapse; font-size: .88rem; }
table.cov th, table.cov td { text-align: left; padding: 8px; border-bottom: 1px solid var(--line-2); vertical-align: top; }
table.cov th { color: var(--muted); font-weight: 500; }
.bar2 { height: 6px; border-radius: 3px; background: var(--line-2); overflow: hidden; min-width: 60px; }
.bar2 i { display: block; height: 100%; background: var(--proved); }

footer { border-top: 1px solid var(--line); padding: 28px 0 40px; color: var(--muted); font-size: .86rem; }
footer .fine { display: inline-block; margin-top: 6px; }
footer .wide { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 12px; }
footer a { color: var(--muted); margin-left: 14px; }

.ptitle .katex { font-size: 1em; }
.h1sub { display: block; font-family: var(--sans); font-size: .95rem; font-weight: 500; color: var(--muted); margin-top: 6px; letter-spacing: 0; }