/* ==========================================================================
   Tendra Teaching Site — visual system
   One stylesheet for every page. No external fonts or scripts: the site is
   opened from disk (file://) and must work offline.
   ========================================================================== */

:root {
  /* palette */
  --bg: #f4f2ec;          /* page */
  --paper: #ffffff;       /* cards */
  --paper-2: #faf8f3;     /* subtle panels */
  --ink: #1d211f;
  --ink-2: #4b524e;
  --ink-3: #7a827d;
  --line: #e2ded4;
  --line-2: #cfc9bb;

  --accent: #1f6f50;      /* forest green — Tendra, actions, correct */
  --accent-ink: #ffffff;
  --accent-soft: #e4f1ea;

  --preseen: #245aa6;     /* blue — real pre-seen facts */
  --preseen-soft: #e6eef9;
  --unseen: #b26a00;      /* amber — invented, unseen detail */
  --unseen-soft: #fbf0dc;
  --warn: #b3261e;        /* red — wrong answers, traps */
  --warn-soft: #fbe7e5;
  --note: #5b4a9c;        /* purple — examiner / exam-angle notes */
  --note-soft: #ece8f7;

  --radius: 10px;
  --radius-s: 6px;
  --shadow: 0 1px 2px rgba(0,0,0,.05), 0 4px 16px rgba(0,0,0,.04);

  --sidebar-w: 292px;
  --rail-w: 220px;
  --maxw: 860px;

  --font-body: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  --font-head: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
  --font-mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #15181a;
    --paper: #1e2225;
    --paper-2: #23282b;
    --ink: #e8e6df;
    --ink-2: #b5b3aa;
    --ink-3: #85847c;
    --line: #2f3538;
    --line-2: #40474b;
    --accent: #5fbf93;
    --accent-ink: #0d1a14;
    --accent-soft: #1b3128;
    --preseen: #7fa8e8;
    --preseen-soft: #1c2738;
    --unseen: #e0a54a;
    --unseen-soft: #33270f;
    --warn: #ef7c74;
    --warn-soft: #3a1c1a;
    --note: #b3a3ec;
    --note-soft: #27223a;
    --shadow: none;
  }
}
:root[data-theme="dark"] {
  --bg: #15181a; --paper: #1e2225; --paper-2: #23282b; --ink: #e8e6df; --ink-2: #b5b3aa;
  --ink-3: #85847c; --line: #2f3538; --line-2: #40474b; --accent: #5fbf93; --accent-ink: #0d1a14;
  --accent-soft: #1b3128; --preseen: #7fa8e8; --preseen-soft: #1c2738; --unseen: #e0a54a;
  --unseen-soft: #33270f; --warn: #ef7c74; --warn-soft: #3a1c1a; --note: #b3a3ec; --note-soft: #27223a;
  --shadow: none;
}

/* --------------------------------------------------------------------------
   Base
   -------------------------------------------------------------------------- */
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.55;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
h1, h2, h3, h4 { font-family: var(--font-head); font-weight: 600; line-height: 1.2; margin: 0 0 .5em; letter-spacing: -.01em; }
h1 { font-size: 2rem; }
h2 { font-size: 1.45rem; margin-top: 0; }
h3 { font-size: 1.15rem; margin-top: 1.4em; }
h4 { font-size: 1rem; margin-top: 1.2em; font-family: var(--font-body); font-weight: 700; }
p { margin: 0 0 1em; }
ul, ol { margin: 0 0 1em; padding-left: 1.4em; }
li { margin: .25em 0; }
strong { font-weight: 650; }
code, .mono { font-family: var(--font-mono); font-size: .92em; }
hr { border: 0; border-top: 1px solid var(--line); margin: 1.6em 0; }
small, .small { font-size: .875rem; color: var(--ink-2); }
.muted { color: var(--ink-3); }
button { font: inherit; }
kbd { font-family: var(--font-mono); font-size: .8em; border: 1px solid var(--line-2); border-bottom-width: 2px; border-radius: 4px; padding: 0 .35em; background: var(--paper-2); }

table { border-collapse: collapse; width: 100%; margin: .6em 0 1.2em; font-size: .95rem; }
th, td { padding: .45em .6em; border-bottom: 1px solid var(--line); text-align: left; vertical-align: top; }
th { font-weight: 650; color: var(--ink-2); font-size: .85rem; text-transform: uppercase; letter-spacing: .03em; }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; }
tr.total td { font-weight: 650; border-top: 2px solid var(--line-2); }
table caption { caption-side: top; text-align: left; font-size: .85rem; color: var(--ink-2); padding: 0 0 .4em; }

/* --------------------------------------------------------------------------
   App shell: persistent sidebar + main
   -------------------------------------------------------------------------- */
.app { display: flex; min-height: 100vh; }

.sidebar {
  width: var(--sidebar-w);
  flex: 0 0 var(--sidebar-w);
  position: sticky; top: 0; height: 100vh; overflow-y: auto;
  background: var(--paper);
  border-right: 1px solid var(--line);
  padding: 18px 14px 40px;
  font-size: .9rem;
}
.sidebar .brand { display: block; padding: 4px 8px 14px; border-bottom: 1px solid var(--line); margin-bottom: 10px; color: var(--ink); }
.sidebar .brand b { font-family: var(--font-head); font-size: 1.15rem; display: block; }
.sidebar .brand span { color: var(--ink-3); font-size: .8rem; }
.sidebar .group { margin: 12px 0 4px; }
.sidebar .group-title { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--ink-3); padding: 6px 8px 4px; font-weight: 650; }
.sidebar a.item, .sidebar span.item {
  display: flex; align-items: flex-start; gap: 8px;
  padding: 6px 8px; border-radius: var(--radius-s); color: var(--ink);
  line-height: 1.3;
}
.sidebar a.item:hover { background: var(--paper-2); text-decoration: none; }
.sidebar .item.active { background: var(--accent-soft); color: var(--accent); font-weight: 650; }
.sidebar span.item { color: var(--ink-3); cursor: default; }
.sidebar .item .t { flex: 1; }
.sidebar .item .tags { display: flex; gap: 3px; margin-top: 2px; flex-shrink: 0; }
.sidebar .item .pri { font-size: .68rem; color: var(--unseen); font-weight: 700; margin-left: 4px; }
.sidebar .item .soon { font-size: .68rem; color: var(--ink-3); margin-left: 4px; font-weight: 500; }
.sidebar .std a.item { font-weight: 600; }

.tag { display: inline-block; font-size: .66rem; font-weight: 700; line-height: 1; padding: 3px 5px; border-radius: 4px; background: var(--paper-2); border: 1px solid var(--line-2); color: var(--ink-2); font-family: var(--font-mono); }
.tag.act-A { border-color: #c9a227; color: #7a5e00; } .tag.act-B { border-color: #d0743a; color: #8a3f10; }
.tag.act-C { border-color: #8a7fd3; color: #4a3fa3; } .tag.act-D { border-color: #4b93c9; color: #1c5a8a; }
.tag.act-E { border-color: #c95b8a; color: #8a2a55; } .tag.act-F { border-color: #4fa37a; color: #1f6f50; }

.main { flex: 1; min-width: 0; padding: 28px 36px 80px; }
.main > .inner { max-width: var(--maxw); margin: 0 auto; }
.main.wide > .inner { max-width: 1080px; }

.topbar { display: none; }

/* --------------------------------------------------------------------------
   Topic header
   -------------------------------------------------------------------------- */
.topic-head { margin-bottom: 18px; }
.topic-head .eyebrow { font-size: .8rem; color: var(--ink-3); text-transform: uppercase; letter-spacing: .08em; margin-bottom: 6px; }
.topic-head h1 { margin-bottom: .3em; }
.topic-head .meta { display: flex; flex-wrap: wrap; gap: 8px 16px; font-size: .875rem; color: var(--ink-2); align-items: center; }
.topic-head .meta .tags { display: inline-flex; gap: 4px; }
.xref { background: var(--paper-2); border: 1px dashed var(--line-2); border-radius: var(--radius-s); padding: 8px 12px; font-size: .85rem; color: var(--ink-2); margin-top: 12px; }
.xref b { color: var(--ink); }

/* Mode bar: the top-level tabs of a topic page */
.modebar {
  display: flex; gap: 4px; border-bottom: 1px solid var(--line); margin: 18px 0 22px;
  position: sticky; top: 0; background: var(--bg); z-index: 5; padding-top: 6px;
}
.modebar button {
  background: none; border: 0; border-bottom: 3px solid transparent; padding: 8px 12px 10px;
  color: var(--ink-2); font-weight: 600; cursor: pointer; font-size: .95rem; margin-bottom: -1px;
}
.modebar button:hover { color: var(--ink); }
.modebar button.active { color: var(--accent); border-bottom-color: var(--accent); }
.modebar button .n { display: inline-block; min-width: 1.4em; padding: 0 .35em; margin-left: .35em; border-radius: 999px; background: var(--paper-2); border: 1px solid var(--line-2); font-size: .72rem; color: var(--ink-3); text-align: center; }

.mode { display: none; }
.mode.active { display: block; }

/* --------------------------------------------------------------------------
   Teach mode: paged sections with a contents rail
   -------------------------------------------------------------------------- */
.teach { display: grid; grid-template-columns: minmax(0, 1fr) var(--rail-w); gap: 28px; align-items: start; }
.rail { position: sticky; top: 64px; font-size: .84rem; }
.rail .rail-title { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--ink-3); font-weight: 650; margin-bottom: 6px; padding-left: 10px; }
.rail ol { list-style: none; margin: 0; padding: 0; border-left: 2px solid var(--line); }
.rail li a { display: block; padding: 5px 10px; color: var(--ink-2); border-left: 2px solid transparent; margin-left: -2px; line-height: 1.3; }
.rail li a:hover { color: var(--ink); text-decoration: none; }
.rail li a.active { color: var(--accent); border-left-color: var(--accent); font-weight: 650; }
.rail li a.done { color: var(--ink-3); }
.rail .progress { margin: 12px 10px 0; height: 4px; background: var(--line); border-radius: 2px; overflow: hidden; }
.rail .progress i { display: block; height: 100%; background: var(--accent); width: 0; transition: width .2s; }

.pages { min-width: 0; }
.pages .page { display: none; }
.pages .page.active { display: block; animation: fade .18s ease-out; }
@keyframes fade { from { opacity: 0; transform: translateY(4px);} to { opacity: 1; transform: none; } }
.page .page-eyebrow { font-size: .78rem; color: var(--ink-3); text-transform: uppercase; letter-spacing: .08em; margin-bottom: 4px; }
.page h2 { font-size: 1.6rem; margin-bottom: .6em; }

.pager { display: flex; justify-content: space-between; align-items: center; gap: 12px; margin-top: 30px; padding-top: 16px; border-top: 1px solid var(--line); }
.pager .btn { max-width: 48%; }
.pager .btn small { display: block; font-size: .72rem; opacity: .75; font-weight: 500; }

/* --------------------------------------------------------------------------
   Buttons
   -------------------------------------------------------------------------- */
.btn {
  display: inline-flex; align-items: center; gap: 6px; padding: 8px 14px; border-radius: 8px;
  border: 1px solid var(--line-2); background: var(--paper); color: var(--ink); font-weight: 600;
  cursor: pointer; text-decoration: none; font-size: .9rem; line-height: 1.25;
}
.btn:hover { border-color: var(--ink-3); text-decoration: none; }
.btn.primary { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.btn.primary:hover { filter: brightness(1.05); }
.btn.ghost { background: transparent; }
.btn.sm { padding: 5px 10px; font-size: .82rem; }
.btn[disabled] { opacity: .45; cursor: default; }

/* --------------------------------------------------------------------------
   Content components
   -------------------------------------------------------------------------- */
.card { background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); padding: 18px 20px; box-shadow: var(--shadow); margin: 0 0 16px; }
.card h3:first-child { margin-top: 0; }

.callout { border-left: 4px solid var(--accent); background: var(--accent-soft); padding: 12px 16px; border-radius: 0 var(--radius-s) var(--radius-s) 0; margin: 1.1em 0; }
.callout.note { border-left-color: var(--note); background: var(--note-soft); }
.callout.warn { border-left-color: var(--warn); background: var(--warn-soft); }
.callout .lbl { display: block; font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; margin-bottom: 4px; opacity: .8; }
.callout p:last-child, .callout ul:last-child { margin-bottom: 0; }

/* Pre-seen extract: real facts, blue */
.preseen { border: 1px solid var(--preseen); background: var(--preseen-soft); border-radius: var(--radius-s); padding: 12px 16px; margin: 1em 0; }
.preseen .lbl { color: var(--preseen); font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; margin-bottom: 6px; display: flex; gap: 8px; align-items: center; }
.preseen p:last-child, .preseen table:last-child, .preseen ul:last-child { margin-bottom: 0; }

/* Unseen: invented, amber. Always carries the label. */
.unseen { border: 1px dashed var(--unseen); background: var(--unseen-soft); border-radius: var(--radius-s); padding: 12px 16px; margin: 1em 0; }
.unseen .lbl { color: var(--unseen); font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; margin-bottom: 6px; }
.unseen p:last-child, .unseen table:last-child, .unseen ul:last-child { margin-bottom: 0; }

/* Citation chip: "pre-seen p.21" */
.cite { display: inline-block; font-family: var(--font-mono); font-size: .72rem; font-weight: 600; color: var(--preseen); background: var(--preseen-soft); border: 1px solid var(--preseen); border-radius: 4px; padding: 0 5px; line-height: 1.5; vertical-align: 1px; white-space: nowrap; }
.cite:hover { text-decoration: none; filter: brightness(.9); }
.cite.derived { color: var(--ink-2); background: var(--paper-2); border-color: var(--line-2); }
.cite.unseen-chip { color: var(--unseen); background: var(--unseen-soft); border-color: var(--unseen); }

/* Worked example */
.worked { border: 1px solid var(--line-2); border-radius: var(--radius); padding: 16px 18px; margin: 1.2em 0; background: var(--paper); }
.worked .lbl { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; color: var(--ink-3); margin-bottom: 6px; }
.worked h4 { margin-top: 0; }
.steps { counter-reset: step; list-style: none; padding: 0; margin: .5em 0 1em; }
.steps li { counter-increment: step; position: relative; padding-left: 2.2em; margin: .55em 0; }
.steps li::before { content: counter(step); position: absolute; left: 0; top: .05em; width: 1.6em; height: 1.6em; border-radius: 50%; background: var(--accent); color: var(--accent-ink); font-size: .78rem; font-weight: 700; display: flex; align-items: center; justify-content: center; }
.calc { font-family: var(--font-mono); font-size: .88rem; background: var(--paper-2); border: 1px solid var(--line); border-radius: var(--radius-s); padding: 10px 12px; margin: .5em 0 1em; white-space: pre; overflow-x: auto; line-height: 1.5; max-width: 100%; }

/* Pros / cons */
.proscons { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 1em 0; }
.proscons > div { border-radius: var(--radius-s); padding: 12px 14px; }
.proscons .pro { background: var(--accent-soft); }
.proscons .con { background: var(--warn-soft); }
.proscons .lbl { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; margin-bottom: 4px; }
.proscons .pro .lbl { color: var(--accent); } .proscons .con .lbl { color: var(--warn); }
.proscons ul { margin: 0; padding-left: 1.1em; font-size: .93rem; }

/* Compare matrix */
.matrix td:first-child { font-weight: 600; white-space: nowrap; }
.matrix td { font-size: .9rem; }

/* Definition */
dl.defs { margin: 0 0 1em; }
dl.defs dt { font-weight: 650; margin-top: .6em; }
dl.defs dd { margin: .1em 0 0 0; color: var(--ink-2); }

/* Recap grid */
.recap { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 10px; }
.recap .card { margin: 0; padding: 12px 14px; font-size: .9rem; }
.recap .card b { display: block; margin-bottom: 4px; }

/* Details */
details { border: 1px solid var(--line); border-radius: var(--radius-s); padding: 0; margin: .8em 0; background: var(--paper-2); }
details summary { cursor: pointer; padding: 9px 14px; font-weight: 600; font-size: .92rem; list-style: none; display: flex; align-items: center; gap: 8px; }
details summary::before { content: "▸"; color: var(--ink-3); font-size: .8em; }
details[open] summary::before { content: "▾"; }
details summary::-webkit-details-marker { display: none; }
details .body { padding: 4px 14px 12px; border-top: 1px solid var(--line); font-size: .93rem; }

/* --------------------------------------------------------------------------
   Questions (rendered by site.js from data/questions.js)
   -------------------------------------------------------------------------- */
.qlist { display: flex; flex-direction: column; gap: 18px; }
.q { background: var(--paper); border: 1px solid var(--line); border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden; }
.q .q-head { display: flex; align-items: center; gap: 10px; padding: 10px 18px; border-bottom: 1px solid var(--line); background: var(--paper-2); font-size: .8rem; color: var(--ink-2); }
.q .q-head .kind { font-weight: 700; text-transform: uppercase; letter-spacing: .06em; font-size: .7rem; padding: 2px 7px; border-radius: 4px; }
.q .q-head .kind.mcq { background: var(--note-soft); color: var(--note); }
.q .q-head .kind.written { background: var(--accent-soft); color: var(--accent); }
.q .q-head .kind.kc { background: var(--preseen-soft); color: var(--preseen); }
.q .q-head .title { font-weight: 600; color: var(--ink); flex: 1; }
.q .q-head .id { font-family: var(--font-mono); color: var(--ink-3); }
.q .q-body { padding: 16px 18px 18px; }
.q .q-body > .preseen, .q .q-body > .unseen { margin-top: 0; }
.q .stem { font-weight: 600; margin: .8em 0 .7em; font-size: 1.02rem; }
.q .task { margin: .8em 0; padding: 12px 14px; background: var(--paper-2); border-radius: var(--radius-s); border: 1px solid var(--line); }
.q .task .lbl { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; color: var(--ink-3); margin-bottom: 4px; }
.q .task p:last-child { margin: 0; }

.opts { display: flex; flex-direction: column; gap: 8px; margin: .4em 0 .6em; }
.opt { display: flex; gap: 10px; align-items: flex-start; border: 1px solid var(--line-2); border-radius: var(--radius-s); padding: 10px 12px; background: var(--paper); cursor: pointer; text-align: left; width: 100%; color: var(--ink); }
.opt:hover { border-color: var(--ink-3); }
.opt .k { flex: 0 0 1.6em; height: 1.6em; border-radius: 50%; border: 1px solid var(--line-2); display: flex; align-items: center; justify-content: center; font-size: .78rem; font-weight: 700; color: var(--ink-2); }
.opt .txt { flex: 1; }
.opt .why { display: none; margin-top: 6px; font-size: .88rem; color: var(--ink-2); border-top: 1px dashed var(--line); padding-top: 6px; }
.q.revealed .opt { cursor: default; }
.q.revealed .opt .why { display: block; }
.q.revealed .opt.correct { border-color: var(--accent); background: var(--accent-soft); }
.q.revealed .opt.correct .k { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
.q.revealed .opt.chosen:not(.correct) { border-color: var(--warn); background: var(--warn-soft); }
.q.revealed .opt.chosen:not(.correct) .k { background: var(--warn); color: #fff; border-color: var(--warn); }
.q .verdict { display: none; font-weight: 650; margin: 6px 0 4px; }
.q.revealed .verdict { display: block; }
.q .verdict.ok { color: var(--accent); } .q .verdict.bad { color: var(--warn); }
.q .takeaway { margin-top: 10px; }

.rubric { border-left: 4px solid var(--note); background: var(--note-soft); padding: 10px 14px; border-radius: 0 var(--radius-s) var(--radius-s) 0; font-size: .88rem; margin: .8em 0; }
.rubric .lbl { font-size: .7rem; text-transform: uppercase; letter-spacing: .08em; font-weight: 700; color: var(--note); margin-bottom: 3px; }
.rubric p { margin: 0; }
.answerbox { margin-top: 12px; }
.answerbox textarea { width: 100%; min-height: 220px; resize: vertical; font: inherit; font-size: .95rem; line-height: 1.5; padding: 12px; border: 1px solid var(--line-2); border-radius: var(--radius-s); background: var(--paper); color: var(--ink); }
.answerbox textarea:focus { outline: 2px solid var(--accent); border-color: var(--accent); }
.answerbox .bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-top: 8px; }
.answerbox .bar .status { font-size: .82rem; color: var(--ink-3); margin-left: auto; }
.answerbox .howto { font-size: .85rem; color: var(--ink-2); margin-top: 8px; }

/* Knowledge check: sort statements into buckets */
.kc-sort .pool { display: flex; flex-wrap: wrap; gap: 8px; margin: .6em 0 1em; min-height: 42px; padding: 8px; border: 1px dashed var(--line-2); border-radius: var(--radius-s); }
.kc-sort .chip { border: 1px solid var(--line-2); background: var(--paper); border-radius: 999px; padding: 6px 12px; font-size: .88rem; cursor: pointer; text-align: left; color: var(--ink); }
.kc-sort .chip.sel { border-color: var(--accent); box-shadow: 0 0 0 2px var(--accent-soft); }
.kc-sort .buckets { display: grid; grid-template-columns: repeat(auto-fit, minmax(190px, 1fr)); gap: 10px; }
.kc-sort .bucket { border: 1px solid var(--line-2); border-radius: var(--radius-s); padding: 8px; min-height: 96px; background: var(--paper-2); cursor: pointer; }
.kc-sort .bucket.target { border-color: var(--accent); background: var(--accent-soft); }
.kc-sort .bucket b { display: block; font-size: .85rem; margin-bottom: 6px; }
.kc-sort .bucket .chip { display: block; width: 100%; margin: 4px 0; border-radius: var(--radius-s); }
.kc-sort .chip.right { border-color: var(--accent); background: var(--accent-soft); }
.kc-sort .chip.wrong { border-color: var(--warn); background: var(--warn-soft); }
.kc-sort .feedback { margin-top: 12px; display: none; }
.kc-sort.revealed .feedback { display: block; }
.kc-sort .feedback dt { font-weight: 650; margin-top: .6em; }
.kc-sort .feedback dd { margin: .15em 0 0; color: var(--ink-2); font-size: .9rem; }

/* Multi-select / true-false checks */
.kc-multi .opt .k { border-radius: 4px; }
.kc-multi .opt.on .k { background: var(--ink-2); color: var(--paper); border-color: var(--ink-2); }

/* Pair link */
.pair { font-size: .8rem; color: var(--ink-3); }

/* Filter bar (mock / formulas) */
.filters { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin: 0 0 18px; }
.filters select, .filters input { font: inherit; padding: 6px 10px; border: 1px solid var(--line-2); border-radius: var(--radius-s); background: var(--paper); color: var(--ink); }
.filters .count { font-size: .85rem; color: var(--ink-3); margin-left: auto; }
.chipbar { display: flex; flex-wrap: wrap; gap: 6px; }
.chipbar button { border: 1px solid var(--line-2); background: var(--paper); border-radius: 999px; padding: 4px 11px; font-size: .82rem; cursor: pointer; color: var(--ink-2); }
.chipbar button.on { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }

/* Formula card */
.formula { border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 16px; background: var(--paper); margin-bottom: 12px; }
.formula .name { font-weight: 650; }
.formula .expr { font-family: var(--font-mono); font-size: .95rem; background: var(--paper-2); border: 1px solid var(--line); border-radius: var(--radius-s); padding: 8px 10px; margin: 6px 0; white-space: pre-wrap; }
.formula .use { font-size: .9rem; color: var(--ink-2); }
.formula .src { font-size: .78rem; color: var(--ink-3); margin-top: 6px; }

/* Podcast */
.podcast { display: flex; gap: 14px; align-items: flex-start; }
.podcast .art { flex: 0 0 56px; height: 56px; border-radius: 10px; background: var(--accent); color: var(--accent-ink); display: flex; align-items: center; justify-content: center; font-family: var(--font-head); font-size: 1.6rem; font-weight: 700; }
.podcast audio { width: 100%; margin-top: 8px; }

/* Status pills (home) */
.pill { display: inline-block; font-size: .72rem; font-weight: 700; border-radius: 999px; padding: 2px 9px; }
.pill.built { background: var(--accent-soft); color: var(--accent); }
.pill.todo { background: var(--paper-2); color: var(--ink-3); border: 1px solid var(--line-2); }
.pill.draft { background: var(--unseen-soft); color: var(--unseen); }

/* Page-anchored pre-seen sections */
.pnum { float: right; font-family: var(--font-mono); font-size: .75rem; color: var(--preseen); background: var(--preseen-soft); border: 1px solid var(--preseen); border-radius: 4px; padding: 1px 6px; }

.two { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }

/* --------------------------------------------------------------------------
   Responsive
   -------------------------------------------------------------------------- */
@media (max-width: 1060px) {
  .teach { grid-template-columns: minmax(0, 1fr); }
  .rail { position: static; display: flex; flex-wrap: wrap; gap: 4px; margin-bottom: 14px; }
  .rail .rail-title { width: 100%; }
  .rail ol { border-left: 0; display: flex; flex-wrap: wrap; gap: 4px; }
  .rail li a { border: 1px solid var(--line-2); border-radius: 999px; padding: 3px 10px; margin: 0; }
  .rail li a.active { background: var(--accent); color: var(--accent-ink); border-color: var(--accent); }
  .rail .progress { display: none; }
}
@media (max-width: 820px) {
  .app { display: block; }
  .topbar { display: flex; position: sticky; top: 0; z-index: 20; background: var(--paper); border-bottom: 1px solid var(--line); padding: 10px 16px; align-items: center; gap: 12px; }
  .topbar b { font-family: var(--font-head); }
  .topbar button { margin-left: auto; }
  .sidebar { position: fixed; top: 0; left: 0; height: 100vh; transform: translateX(-100%); transition: transform .2s; z-index: 30; width: min(320px, 90vw); box-shadow: 0 0 40px rgba(0,0,0,.25); }
  body.nav-open .sidebar { transform: none; }
  .main { padding: 18px 16px 60px; }
  .modebar { overflow-x: auto; top: 49px; }
  .modebar button { white-space: nowrap; }
  .proscons, .two { grid-template-columns: 1fr; }
  h1 { font-size: 1.6rem; }
  .page h2 { font-size: 1.35rem; }
  table { font-size: .88rem; }
  .pager .btn { max-width: none; }
}
@media print {
  .sidebar, .modebar, .pager, .topbar, .rail { display: none !important; }
  .mode, .pages .page { display: block !important; }
  .main { padding: 0; }
}