:root {
  --bg: #f6f5f1;
  --panel: #ffffff;
  --ink: #1c1c22;
  --ink-body: #35353d;
  --muted: #6f6f7a;
  --faint: #9898a6;
  --line: #e8e6ef;
  --line-soft: #f1eff6;
  --brand: #5b4bd6;
  --brand-ink: #4536b0;
  --brand-soft: #ece9fb;
  --brand-softer: #f5f3fc;
  /* per-subject accent, set by JS; falls back to brand */
  --accent: var(--subj-color, var(--brand));
  --accent-soft: color-mix(in srgb, var(--accent) 12%, #fff);
  --accent-softer: color-mix(in srgb, var(--accent) 6%, #fff);
  --accent-ink: color-mix(in srgb, var(--accent) 78%, #000);
  --radius: 16px;
  --radius-sm: 11px;
  --shadow: 0 1px 2px rgba(30, 25, 70, .04), 0 12px 32px -14px rgba(40, 33, 100, .14);
  --shadow-hover: 0 2px 4px rgba(30, 25, 70, .05), 0 18px 44px -16px rgba(40, 33, 100, .2);
  --shadow-lg: 0 30px 70px -24px rgba(35, 25, 90, .42);
  --focus-ring: 0 0 0 2px #fff, 0 0 0 4px var(--accent);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: "DM Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  background:
    radial-gradient(1100px 520px at 82% -10%, color-mix(in srgb, var(--accent) 7%, transparent), transparent 62%),
    radial-gradient(900px 500px at -12% 8%, #efedf8, transparent 55%),
    var(--bg);
  color: var(--ink);
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
h1, h2, h3, h4, .head-font { font-family: "Space Grotesk", "DM Sans", sans-serif; letter-spacing: -.02em; }
::selection { background: color-mix(in srgb, var(--accent) 22%, #fff); }

/* keyboard focus */
:focus-visible { outline: none; box-shadow: var(--focus-ring); border-radius: 8px; }

/* thin, quiet scrollbars for inner panes */
#sidebar, #sol-body, #modal-body, #cmdk-results, #tabs { scrollbar-width: thin; scrollbar-color: #cfcbdf transparent; }

/* ---------- header ---------- */
#topbar {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255, 255, 255, .78);
  backdrop-filter: saturate(1.4) blur(16px);
  -webkit-backdrop-filter: saturate(1.4) blur(16px);
  border-bottom: 1px solid var(--line);
  padding: 13px 26px 0;
}
.topbar-row { display: flex; align-items: center; justify-content: space-between; gap: 20px; max-width: 1320px; margin: 0 auto; }
.brand { display: flex; align-items: center; }
.wordmark {
  margin: 0; font-family: "Space Grotesk", sans-serif; font-weight: 700;
  font-size: 26px; letter-spacing: -.035em; line-height: 1; color: var(--ink);
}
.wordmark span { color: var(--brand); }

/* command-bar trigger */
#cmdk-open {
  display: flex; align-items: center; gap: 10px; cursor: pointer;
  font: inherit; font-size: 13.5px; color: var(--faint);
  background: #fff; border: 1px solid var(--line);
  border-radius: 11px; padding: 9px 13px; width: min(340px, 42vw);
  box-shadow: 0 1px 2px rgba(30, 25, 70, .04);
  transition: border-color .15s, box-shadow .15s;
}
#cmdk-open:hover { border-color: #cfc6f0; box-shadow: 0 2px 8px rgba(60, 45, 140, .1); }
#cmdk-open:active { transform: translateY(1px); }
.cmdk-text { flex: 1; text-align: left; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.cmdk-key { font-family: "Space Grotesk", sans-serif; font-size: 11px; font-weight: 600; color: var(--brand-ink); background: var(--brand-soft); border-radius: 6px; padding: 2px 7px; }
.cmdk-ico { width: 15px; height: 15px; flex: 0 0 15px; border: 1.9px solid #b6aee0; border-radius: 50%; position: relative; }
.cmdk-ico::after { content: ""; position: absolute; right: -4px; bottom: -3px; width: 6px; height: 1.9px; background: #b6aee0; transform: rotate(45deg); border-radius: 2px; }
.cmdk-ico.big { width: 18px; height: 18px; flex-basis: 18px; border-color: var(--brand); }
.cmdk-ico.big::after { background: var(--brand); }

#tabs { display: flex; gap: 4px; margin-top: 10px; overflow-x: auto; max-width: 1320px; margin-left: auto; margin-right: auto; }
#tabs button {
  appearance: none; border: none; background: none; cursor: pointer;
  font: inherit; font-size: 14px; font-weight: 600; font-family: "Space Grotesk", sans-serif;
  padding: 10px 14px; color: var(--muted);
  border-bottom: 3px solid transparent; border-radius: 10px 10px 0 0;
  white-space: nowrap; transition: color .15s, background .15s;
}
#tabs button:hover { background: color-mix(in srgb, var(--tab-color, var(--brand)) 7%, transparent); color: var(--ink); }
#tabs button.active {
  color: color-mix(in srgb, var(--tab-color, var(--brand)) 82%, #000);
  background: color-mix(in srgb, var(--tab-color, var(--brand)) 9%, transparent);
  border-bottom-color: var(--tab-color, var(--brand));
}

#protocol-warning {
  background: #fff5d6; color: #664d03; padding: 10px 26px; font-size: 14px;
  border-bottom: 1px solid #f4e3a1;
}
.hidden { display: none !important; }

/* ---------- layout ---------- */
#layout { display: flex; gap: 28px; max-width: 1320px; margin: 0 auto; padding: 26px 26px 90px; }
#sidebar { width: 312px; flex: 0 0 312px; position: sticky; top: calc(var(--topbar-h, 112px) + 14px); align-self: flex-start; max-height: calc(100vh - var(--topbar-h, 112px) - 30px); overflow-y: auto; padding-right: 4px; }
#content { flex: 1; min-width: 0; }
#layout.sidebar-hidden #sidebar { display: none; }

/* Summary/Practice row — sticks to the top of the sidebar while the TOC scrolls */
.sidebar-top {
  position: sticky; top: 0; z-index: 3;
  background: var(--bg); padding-bottom: 14px; margin-bottom: 6px;
}
.sidebar-top .view-switch { margin-bottom: 0; }
/* collapse button lives INSIDE the Summary/Practice pill, on the right */
#sidebar-collapse {
  flex: 0 0 auto !important; width: 36px; padding: 8px 0 !important;
  display: inline-flex; align-items: center; justify-content: center;
  color: var(--muted); margin-left: 2px;
}
#sidebar-collapse:hover { background: #fff; color: var(--brand); box-shadow: 0 1px 3px rgba(40, 30, 90, .1); }
/* Floating "show panel" button — only visible when the sidebar is hidden */
#sidebar-show {
  position: fixed; left: 18px; bottom: 22px; z-index: 60;
  display: none; align-items: center; gap: 8px;
  padding: 9px 14px 9px 11px; border-radius: 11px;
  border: 1px solid var(--line); background: #fff; color: var(--ink);
  font-family: inherit; font-size: 13.5px; font-weight: 600; cursor: pointer;
  box-shadow: 0 6px 20px rgba(40, 30, 90, .16); transition: border-color .15s, color .15s, transform .15s;
}
#sidebar-show:hover { color: var(--brand); border-color: #cfc6f0; transform: translateY(-1px); }
body.sidebar-hidden #sidebar-show { display: inline-flex; }

.view-switch { display: flex; gap: 4px; background: #eceaf4; border-radius: 11px; padding: 4px; margin-bottom: 20px; }
.view-switch button {
  flex: 1; appearance: none; border: none; background: none; cursor: pointer;
  font: inherit; font-size: 13.5px; font-weight: 600; padding: 8px 4px; border-radius: 8px; color: var(--muted);
  transition: background .15s, color .15s, box-shadow .15s;
}
.view-switch button.active { background: #fff; color: var(--ink); box-shadow: 0 1px 3px rgba(40, 30, 90, .12); }

.toc-head { font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: .12em; color: var(--faint); margin: 2px 0 14px 2px; }

/* ---------- concept spine (summary) ---------- */
#toc.spine { position: relative; padding-left: 2px; }
#toc.spine::before {
  content: ""; position: absolute; left: 11px; top: 12px; bottom: 14px; width: 2px;
  background: linear-gradient(to bottom, color-mix(in srgb, var(--accent) 30%, var(--line)), var(--line));
}
.spine-node { position: relative; display: flex; gap: 13px; align-items: flex-start; padding: 3px 0 3px; }
.spine-node .dot {
  width: 12px; height: 12px; flex: 0 0 12px; margin-top: 9px; border-radius: 50%;
  background: #fff; border: 2px solid #c9c4e0; z-index: 1; transition: all .15s;
}
.spine-node .node-body { flex: 1; min-width: 0; border-radius: 12px; padding: 7px 11px; cursor: pointer; }
.spine-node .node-title { font-family: "Space Grotesk", sans-serif; font-size: 13.5px; font-weight: 600; color: #5c5c66; line-height: 1.35; display: flex; gap: 8px; }
.spine-node .node-title .n { color: var(--faint); font-weight: 700; }
.spine-node:hover .node-body { background: var(--accent-softer); }
.spine-node:hover .dot { border-color: var(--accent); }
.spine-node.current .dot { background: var(--accent); border-color: color-mix(in srgb, var(--accent) 30%, #fff); width: 15px; height: 15px; flex-basis: 15px; margin-top: 7px; }
.spine-node.current .node-body {
  background: #fff; border: 1px solid color-mix(in srgb, var(--accent) 22%, var(--line));
  box-shadow: 0 4px 14px -6px color-mix(in srgb, var(--accent) 30%, transparent); cursor: default;
}
.spine-node.current .node-title { color: var(--ink); }
.spine-terms { display: none; flex-wrap: wrap; gap: 5px; margin-top: 9px; }
.spine-node.current .spine-terms { display: flex; }
.spine-term {
  appearance: none; cursor: pointer; font: inherit;
  font-size: 11.5px; font-weight: 500; line-height: 1.2;
  background: var(--accent-soft); color: var(--accent-ink);
  border: 1px solid transparent; border-radius: 7px; padding: 4px 8px; text-align: left;
  transition: border-color .12s, transform .1s;
}
.spine-term:hover { border-color: var(--accent); }
.spine-term:active { transform: scale(.97); }

/* plain TOC (practice) */
#toc.plain a {
  display: flex; gap: 9px; align-items: baseline;
  padding: 8px 11px; border-radius: 9px;
  color: var(--ink); text-decoration: none; font-size: 13.5px;
}
#toc.plain a:hover { background: var(--accent-softer); }
#toc.plain a.current { background: var(--accent); color: #fff; }
#toc.plain a.current .toc-num { color: rgba(255, 255, 255, .8); }
.toc-num { font-weight: 700; font-size: 12px; color: var(--accent); min-width: 22px; font-family: "Space Grotesk", sans-serif; }

/* ---------- subject header ---------- */
.subject-hero {
  background:
    radial-gradient(560px 190px at 100% 0%, color-mix(in srgb, var(--accent) 9%, transparent), transparent 70%),
    var(--panel);
  border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 26px 30px; margin-bottom: 22px; position: relative; overflow: hidden;
}
.subject-hero::before {
  content: ""; position: absolute; left: 0; top: 0; bottom: 0; width: 5px;
  background: linear-gradient(to bottom, var(--accent), color-mix(in srgb, var(--accent) 45%, #fff));
}
.subject-hero h2 { margin: 0 0 8px; font-size: 27px; letter-spacing: -.025em; }
.subject-hero p { margin: 0; color: var(--muted); font-size: 14.5px; max-width: 70ch; }
.subject-hero .meta { margin-top: 13px; font-size: 12.5px; color: var(--faint); font-family: "Space Grotesk", sans-serif; letter-spacing: .01em; }

/* ---------- topic cards ---------- */
.topic {
  background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 24px 28px; margin-bottom: 22px;
  scroll-margin-top: 112px;
  transition: box-shadow .2s, border-color .2s;
}
.topic:hover { box-shadow: var(--shadow-hover); border-color: color-mix(in srgb, var(--accent) 14%, var(--line)); }
.topic-head { display: flex; align-items: center; gap: 13px; flex-wrap: wrap; padding-bottom: 13px; border-bottom: 1px solid var(--line-soft); }
.topic-num {
  background: var(--accent); color: #fff; font-weight: 700; font-size: 13px; font-family: "Space Grotesk", sans-serif;
  border-radius: 9px; padding: 4px 11px;
  box-shadow: 0 2px 6px -2px color-mix(in srgb, var(--accent) 55%, transparent);
}
.topic h3 { margin: 0; font-size: 20px; flex: 1; line-height: 1.2; }
.lecture-link { font-size: 11.5px; font-weight: 600; color: var(--accent-ink); text-decoration: none; white-space: nowrap; background: var(--accent-soft); padding: 4px 10px; border-radius: 7px; transition: filter .12s; }
.lecture-link:hover { filter: brightness(.95); }

.summary { font-size: 15px; margin-top: 14px; color: var(--ink-body); }
.summary p { margin: 10px 0; }
.summary ul, .summary ol { margin: 8px 0; padding-left: 22px; }
.summary li { margin: 4px 0; }
.summary b { color: #16161a; font-weight: 600; }
.summary .formula {
  display: block; background: #f7f6fb; border: 1px solid var(--line); border-radius: 9px;
  padding: 9px 14px; margin: 11px 0; font-family: "SF Mono", Menlo, monospace; font-size: 13.2px; overflow-x: auto;
}
.summary table { border-collapse: collapse; margin: 11px 0; font-size: 13.5px; }
.summary th, .summary td { border: 1px solid var(--line); padding: 6px 11px; text-align: left; }
.summary th { background: #f7f6fb; }

a.cite {
  color: var(--accent-ink); cursor: pointer; text-decoration: none;
  font-size: .82em; font-weight: 700; white-space: nowrap;
  background: var(--accent-soft); border-radius: 6px; padding: 1px 6px;
  transition: filter .12s;
}
a.cite:hover { filter: brightness(.93); }

/* key terms */
.terms-head, .res-head, .ex-topic-head {
  font-size: 11px; font-weight: 700; text-transform: uppercase; letter-spacing: .1em;
  color: var(--faint); margin: 22px 0 10px;
}
.terms { display: flex; flex-wrap: wrap; gap: 8px; }
.term-chip {
  appearance: none; cursor: pointer; font: inherit; font-size: 13px; font-weight: 600;
  background: #fff; color: var(--ink-body);
  border: 1px solid var(--line); border-radius: 9px; padding: 6px 12px;
  transition: border-color .12s, color .12s, background .12s, transform .1s;
}
.term-chip:hover { border-color: var(--accent); color: var(--accent-ink); background: var(--accent-softer); }
.term-chip:active { transform: scale(.97); }
.term-chip .pg { font-weight: 500; font-size: 11px; color: var(--faint); margin-left: 6px; }

/* resources */
.res-list { list-style: none; margin: 0; padding: 0; }
.res-list li { display: flex; gap: 10px; align-items: baseline; padding: 5px 0; font-size: 14px; }
.res-list a { color: var(--accent-ink); font-weight: 600; text-decoration: none; }
.res-list a:hover { text-decoration: underline; }
.res-note { color: var(--muted); font-size: 12.8px; }

/* ---------- practice ---------- */
.ex-topic { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); padding: 22px 28px; margin-bottom: 22px; scroll-margin-top: 112px; }
.ex-topic > h3 { margin: 0 0 4px; font-size: 18px; display: flex; align-items: baseline; gap: 10px; }
.ex-topic > .ex-topic-sub { color: var(--muted); font-size: 13px; margin-bottom: 4px; }
.exercise { border: 1px solid var(--line); border-radius: 12px; padding: 15px 17px; margin-top: 13px; background: color-mix(in srgb, var(--bg) 35%, #fff); transition: border-color .15s; }
.exercise:hover { border-color: color-mix(in srgb, var(--accent) 20%, var(--line)); }
.exercise-head { display: flex; align-items: baseline; gap: 10px; flex-wrap: wrap; }
.exercise-head h4 { margin: 0; font-size: 15px; flex: 1; }
.ex-links { display: flex; gap: 8px; flex-wrap: wrap; }
.ex-links a, .ex-links span.nolink, .ex-links button.solbtn {
  font-size: 12.3px; font-weight: 700; text-decoration: none; border-radius: 8px; padding: 5px 12px;
  border: none; cursor: pointer; font-family: inherit;
  transition: transform .1s, filter .12s;
}
.ex-links a:active, .ex-links button.solbtn:active { transform: translateY(1px); }
.ex-links button.solbtn { background: var(--accent); color: #fff; box-shadow: 0 2px 6px -2px color-mix(in srgb, var(--accent) 55%, transparent); }
.ex-links button.solbtn:hover { filter: brightness(1.06); }
.ex-links a.task { background: var(--accent-soft); color: var(--accent-ink); }
.ex-links a.task:hover { filter: brightness(.96); }
.ex-links a.sol { background: #e6f4ea; color: #1e7d36; }
.ex-links span.nolink { background: #f1f3f5; color: var(--muted); font-weight: 600; }
.exercise .desc { font-size: 13.8px; color: var(--muted); margin: 7px 0 0; }

/* ---------- ⌘K command palette ---------- */
#cmdk-backdrop {
  position: fixed; inset: 0; z-index: 120;
  background: rgba(28, 22, 55, .42); backdrop-filter: blur(4px);
  display: flex; align-items: flex-start; justify-content: center; padding: 12vh 24px 24px;
}
#cmdk {
  background: #fff; width: min(620px, 100%); border-radius: 16px; overflow: hidden;
  box-shadow: var(--shadow-lg); display: flex; flex-direction: column; max-height: 70vh;
  border: 1px solid var(--line);
}
#cmdk-inputrow { display: flex; align-items: center; gap: 12px; padding: 16px 18px; border-bottom: 1px solid var(--line); }
#cmdk-input { flex: 1; border: none; outline: none; font: inherit; font-size: 17px; color: var(--ink); background: none; }
#cmdk-input::placeholder { color: var(--faint); }
.cmdk-esc { font-size: 11px; font-weight: 600; color: var(--faint); background: #f1eff7; border-radius: 6px; padding: 3px 7px; }
#cmdk-results { overflow-y: auto; padding: 8px; }
.cmdk-group { font-size: 10.5px; font-weight: 700; letter-spacing: .1em; text-transform: uppercase; color: var(--faint); padding: 10px 10px 6px; }
.cmdk-item { display: flex; align-items: center; gap: 12px; padding: 9px 11px; border-radius: 10px; cursor: pointer; }
.cmdk-item.active { background: var(--brand-softer); }
.cmdk-item .ci-badge { font-size: 10.5px; font-weight: 700; font-family: "Space Grotesk", sans-serif; color: #fff; border-radius: 6px; padding: 3px 7px; flex: 0 0 auto; }
.cmdk-item .ci-main { flex: 1; min-width: 0; display: flex; flex-direction: column; gap: 1px; }
.cmdk-item .ci-title { font-size: 14px; font-weight: 600; color: var(--ink); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.cmdk-item .ci-sub { font-size: 12px; color: var(--muted); white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.cmdk-item .ci-kind { font-size: 11px; color: var(--faint); flex: 0 0 auto; }
.cmdk-empty { padding: 30px 14px; text-align: center; color: var(--faint); font-size: 14px; }
#cmdk-foot { display: flex; gap: 16px; padding: 10px 16px; border-top: 1px solid var(--line); font-size: 11.5px; color: var(--faint); }
#cmdk-foot b { color: var(--muted); font-weight: 700; }

/* ---------- worked-solution modal ---------- */
#sol-backdrop { position: fixed; inset: 0; z-index: 100; background: rgba(28, 22, 55, .5); backdrop-filter: blur(4px); display: flex; align-items: center; justify-content: center; padding: 24px; }
#sol-modal { background: var(--panel); border-radius: 18px; box-shadow: var(--shadow-lg); width: min(900px, 100%); max-height: 92vh; display: flex; flex-direction: column; overflow: hidden; border: 1px solid var(--line); }
#sol-head { display: flex; align-items: flex-start; gap: 14px; padding: 18px 24px 14px; border-bottom: 1px solid var(--line); }
#sol-titlebox { flex: 1; min-width: 0; }
#sol-title { margin: 0; font-size: 19px; }
#sol-sub { color: var(--muted); font-size: 12.8px; margin-top: 2px; }
#sol-close, #modal-close { appearance: none; border: none; cursor: pointer; background: #f1eff7; color: var(--muted); width: 34px; height: 34px; border-radius: 9px; font-size: 16px; flex: 0 0 34px; transition: background .12s, color .12s, transform .1s; }
#sol-close:hover, #modal-close:hover { background: #e7e2f4; color: var(--ink); }
#sol-close:active, #modal-close:active { transform: scale(.94); }
#sol-body { overflow-y: auto; padding: 18px 24px 26px; }

.sol-links { display: flex; gap: 8px; flex-wrap: wrap; margin-bottom: 4px; }
.sol-links a { font-size: 12.5px; font-weight: 700; text-decoration: none; border-radius: 9px; padding: 7px 14px; transition: filter .12s, transform .1s; }
.sol-links a:active { transform: translateY(1px); }
.sol-links a.task { background: var(--accent-soft); color: var(--accent-ink); }
.sol-links a.sol { background: #e6f4ea; color: #1e7d36; }
.sol-pw { font-size: 12.5px; color: var(--muted); margin: 8px 0 2px; }
.sol-pw code { background: #f1eff7; border-radius: 5px; padding: 1px 6px; font-family: "SF Mono", Menlo, monospace; color: var(--ink); font-weight: 700; }
.sol-desc { font-size: 13.6px; color: var(--muted); margin: 10px 0 4px; }

.step { background: color-mix(in srgb, var(--bg) 72%, #fff); border-radius: 12px; padding: 13px 17px; margin-top: 13px; border-left: 3px solid var(--accent); }
.step-title { font-size: 14px; font-weight: 700; color: var(--ink); margin-bottom: 6px; }
.step-body { font-size: 13.4px; color: #3a3a44; line-height: 1.7; }
.step-body ul, .step-body ol { margin: 6px 0; padding-left: 20px; }
.step-body li { margin: 3px 0; }
.step-body b, .step-body strong { color: #16161a; }
.step .formula, .formula { background: var(--panel); border: 1px solid var(--line); border-radius: 9px; padding: 10px 14px; margin: 8px 0; font-family: "SF Mono", Menlo, monospace; font-size: 12.6px; color: var(--ink); overflow-x: auto; line-height: 1.65; white-space: pre-wrap; }
.step-body p { margin: 7px 0; }
.step-body p:first-child { margin-top: 0; }
/* division between answer parts (a)/(b)/(c)… */
.part { padding-top: 11px; margin-top: 11px; border-top: 1px dashed var(--line); }
.part:first-child { padding-top: 0; margin-top: 0; border-top: none; }
.part > .part-label { display: inline-block; font-weight: 700; color: var(--accent-ink); margin-right: 6px; }
.part-head { font-weight: 700; color: var(--ink); margin-bottom: 5px; }
.part-head .part-label { color: var(--accent-ink); margin-right: 6px; }
/* KaTeX sizing inside solution/summary text */
.step-body .katex, .def .katex, .example .katex, .desc .katex, .summary .katex { font-size: 1.04em; }
.step-body .katex-display { margin: 9px 0; text-align: left; }
.step-body .katex-display > .katex { text-align: left; }
.result { background: var(--brand-soft); border-radius: 8px; padding: 5px 12px; display: inline-block; font-weight: 700; font-size: 13px; color: var(--brand-ink); margin-top: 4px; }
.result.red { background: #fcebeb; color: #a32d2d; }
.result.green { background: #eaf3de; color: #3b6d11; }
.result.amber { background: #faeeda; color: #854f0b; }
.grid2 { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
table.calc { width: 100%; border-collapse: collapse; font-size: 13px; margin: 7px 0; font-variant-numeric: tabular-nums; }
table.calc th { text-align: left; padding: 6px 10px; background: var(--panel); color: var(--muted); font-weight: 600; font-size: 12px; border-bottom: 1px solid var(--line); }
table.calc td { padding: 6px 10px; border-top: 1px solid var(--line); color: var(--ink); }
table.calc tbody tr:hover td { background: color-mix(in srgb, var(--accent) 4%, transparent); }
table.calc td.num { text-align: right; font-family: "SF Mono", Menlo, monospace; font-size: 12.4px; }
table.calc tr.total td { font-weight: 700; border-top: 1.5px solid var(--muted); }
.step-note { font-size: 12.3px; color: var(--muted); margin-top: 7px; font-style: italic; }
@media (max-width: 620px) { .grid2 { grid-template-columns: 1fr; } }

/* ---------- term / citation modal ---------- */
#modal-backdrop { position: fixed; inset: 0; z-index: 100; background: rgba(28, 22, 55, .5); backdrop-filter: blur(4px); display: flex; align-items: center; justify-content: center; padding: 24px; }
#modal { background: var(--panel); border-radius: 18px; box-shadow: var(--shadow-lg); width: min(880px, 100%); max-height: 92vh; display: flex; flex-direction: column; overflow: hidden; border: 1px solid var(--line); }
#modal-head { display: flex; align-items: flex-start; gap: 14px; padding: 18px 22px 14px; border-bottom: 1px solid var(--line); }
#modal-titlebox { flex: 1; min-width: 0; }
#modal-title { margin: 0; font-size: 20px; }
#modal-sub { color: var(--muted); font-size: 12.8px; margin-top: 3px; }
#modal-body { overflow-y: auto; padding: 16px 22px 22px; }
#modal-info { font-size: 14.5px; color: var(--ink-body); }
#modal-info .def { margin: 4px 0 10px; }
#modal-info .example {
  background: var(--accent-softer); border: 1px solid color-mix(in srgb, var(--accent) 14%, var(--line));
  border-radius: 10px;
  padding: 11px 15px; margin: 12px 0; font-size: 13.7px; color: #3a3a44;
}
#modal-info .example::before { content: "Example · from the slides"; display: block; font-size: 10.5px; font-weight: 700; letter-spacing: .08em; text-transform: uppercase; color: var(--accent-ink); margin-bottom: 5px; }
#modal-srcline { font-size: 13px; color: var(--muted); margin: 10px 0 7px; }
#modal-srcline b { color: var(--ink); }
#page-nav { display: flex; align-items: center; gap: 10px; margin-bottom: 9px; font-size: 13px; }
#page-nav button { appearance: none; cursor: pointer; font: inherit; font-size: 12.5px; font-weight: 600; background: #f4f2fa; border: 1px solid var(--line); border-radius: 8px; padding: 5px 11px; transition: background .12s, transform .1s; }
#page-nav button:hover:not(:disabled) { background: #ece9f5; }
#page-nav button:active:not(:disabled) { transform: translateY(1px); }
#page-nav button:disabled { opacity: .4; cursor: default; }
#pg-label { font-size: 12px; color: var(--faint); font-family: "Space Grotesk", sans-serif; font-variant-numeric: tabular-nums; }
#pg-open { margin-left: auto; font-size: 12.5px; font-weight: 700; color: var(--brand-ink); text-decoration: none; }
#pg-open:hover { text-decoration: underline; }
#canvas-wrap { position: relative; border: 1px solid var(--line); border-radius: 12px; overflow: hidden; background: #faf9fd; min-height: 130px; }
#canvas-spinner { position: absolute; inset: 0; display: flex; align-items: center; justify-content: center; color: var(--faint); font-size: 13.5px; text-align: center; padding: 20px; }
#canvas-spinner a { color: var(--brand-ink); }
#pdf-canvas { display: block; width: 100%; height: auto; }

/* reduced motion: keep everything readable, stop the movement */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition: none !important; animation: none !important; }
}

/* responsive */
@media (max-width: 900px) {
  #layout { flex-direction: column; }
  #sidebar { position: static; width: 100%; flex: none; max-height: none; }
  #cmdk-open { width: 200px; }
  .cmdk-text { display: none; }
}