:root {
  --bg: #f6f5f1;
  --surface: #ffffff;
  --surface-2: #f0eee8;
  --border: #d9d5ca;
  --text: #1f2328;
  --muted: #5f6672;
  --accent: #0b5f8a;
  --accent-text: #ffffff;
  --pass: #1a7f4b;
  --fail: #b3261e;
  --pass-bg: #e6f4ec;
  --fail-bg: #fbeae8;
  --note-bg: #fff7e0;
  --note-border: #d9a400;
  --code-bg: #f3f1ea;
  --kw: #8a2f86;
  --str: #9a4b00;
  --num: #0b6e6e;
  --com: #6b7280;
  --def: #0b5f8a;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --serif: Charter, "Bitstream Charter", "Iowan Old Style", Georgia, serif;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #15171a;
    --surface: #1d2024;
    --surface-2: #24282d;
    --border: #363b42;
    --text: #e4e6ea;
    --muted: #9aa3ae;
    --accent: #6cb6e0;
    --accent-text: #0c1014;
    --pass: #5fc98e;
    --fail: #f28b82;
    --pass-bg: #18301f;
    --fail-bg: #3a1c1a;
    --note-bg: #332b12;
    --note-border: #c79a12;
    --code-bg: #24282d;
    --kw: #d7a6ee;
    --str: #e8b877;
    --num: #7fd4d0;
    --com: #8b949e;
    --def: #8cc8f0;
  }
}

* { box-sizing: border-box; }

html, body { height: 100%; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 15px/1.5 var(--sans);
  display: flex;
  flex-direction: column;
}

.visually-hidden {
  position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap;
}

/* ---------- top bar ---------- */

.topbar {
  display: flex; align-items: center; gap: 16px;
  padding: 10px 16px;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.brand { font-weight: 650; white-space: nowrap; }
.picker { flex: 1 1 auto; min-width: 0; }
.picker select {
  width: 100%; max-width: 46rem;
  font: inherit; color: var(--text);
  background: var(--surface-2); border: 1px solid var(--border); border-radius: 6px;
  padding: 6px 8px;
}
.engine-status { font-size: 13px; color: var(--muted); white-space: nowrap; }
.engine-status::before {
  content: ""; display: inline-block; width: 8px; height: 8px; border-radius: 50%;
  margin-right: 6px; background: var(--muted);
}
.engine-status[data-kind="ready"]::before { background: var(--pass); }
.engine-status[data-kind="busy"]::before { background: var(--note-border); }
.engine-status[data-kind="error"]::before { background: var(--fail); }

/* ---------- layout ---------- */

.layout {
  flex: 1 1 auto; min-height: 0; overflow: hidden;
  display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); grid-template-rows: minmax(0, 1fr);
}
.layout[hidden] { display: none; }
.pane { min-width: 0; min-height: 0; display: flex; flex-direction: column; }
.docs { border-right: 1px solid var(--border); background: var(--surface); }

.tabs { display: flex; gap: 2px; padding: 8px 16px 0; border-bottom: 1px solid var(--border); }
.tab {
  font: inherit; color: var(--muted); background: none; border: 0;
  border-bottom: 2px solid transparent; padding: 6px 10px 8px; cursor: pointer;
}
.tab[aria-selected="true"] { color: var(--text); border-bottom-color: var(--accent); font-weight: 600; }
.tab:focus-visible, button:focus-visible, select:focus-visible, textarea:focus-visible, .doc:focus-visible {
  outline: 2px solid var(--accent); outline-offset: 2px;
}

/* ---------- reading ---------- */

/* position: relative keeps KaTeX's absolutely positioned accessibility nodes inside this scroller */
.doc { flex: 1 1 auto; overflow: auto; padding: 20px 28px 48px; position: relative; }
.doc > div, .doc > .context-banner { max-width: 44rem; margin-left: auto; margin-right: auto; }
.doc > div { font: 17px/1.62 var(--serif); }
.context-banner {
  font-size: 13px; color: var(--muted); letter-spacing: 0.01em;
  border-bottom: 1px solid var(--border); padding-bottom: 8px; margin-top: 0;
}
.doc h1 { font: 650 26px/1.25 var(--sans); margin: 0.4em 0 0.6em; }
.doc h2 { font: 650 19px/1.3 var(--sans); margin: 1.9em 0 0.5em; }
.doc h3 { font: 650 16px/1.3 var(--sans); margin: 1.5em 0 0.4em; }
.doc p, .doc ul, .doc ol { margin: 0 0 0.9em; }
.doc li { margin-bottom: 0.3em; }
.doc code { font: 0.86em var(--mono); background: var(--code-bg); padding: 0.1em 0.3em; border-radius: 4px; }
.doc pre {
  font: 13.5px/1.5 var(--mono); background: var(--code-bg);
  border: 1px solid var(--border); border-radius: 6px;
  padding: 10px 12px; overflow-x: auto; margin: 0 0 1em;
}
.doc pre code { background: none; padding: 0; font-size: inherit; }
.doc pre.source { max-width: none; font-size: 13px; }
.doc blockquote {
  margin: 1.1em 0; padding: 10px 14px;
  background: var(--note-bg); border-left: 4px solid var(--note-border); border-radius: 0 6px 6px 0;
}
.doc blockquote p:last-child { margin-bottom: 0; }
.doc details {
  margin: 1.2em 0; border: 1px solid var(--border); border-radius: 6px; background: var(--surface-2);
}
.doc details > summary { cursor: pointer; padding: 8px 12px; font: 600 15px var(--sans); }
.doc details[open] > summary { border-bottom: 1px solid var(--border); }
.doc details > :not(summary) { margin-left: 12px; margin-right: 12px; }
.doc details > :nth-child(2) { margin-top: 12px; }
.doc img { max-width: 100%; height: auto; background: #ffffff; border-radius: 6px; padding: 6px; }
.table-wrap { overflow-x: auto; margin: 0 0 1em; }
.doc table { border-collapse: collapse; font: 14.5px/1.4 var(--sans); }
.doc th, .doc td { border-bottom: 1px solid var(--border); padding: 6px 10px; text-align: left; vertical-align: top; }
.doc th { font-weight: 650; border-bottom-width: 2px; }
.doc .katex-display { overflow-x: auto; overflow-y: hidden; padding: 2px 0; }

/* ---------- workspace ---------- */

.work { background: var(--bg); overflow-y: auto; }
.work-head {
  display: flex; justify-content: space-between; align-items: baseline;
  padding: 10px 16px 6px; font-size: 13px; color: var(--muted);
}
.file-label { font-family: var(--mono); }
.editor { flex: 1 1 55%; min-height: 220px; border-top: 1px solid var(--border); border-bottom: 1px solid var(--border); }
.CodeMirror {
  height: 100%; font: 13.5px/1.5 var(--mono);
  background: var(--surface); color: var(--text);
}
.CodeMirror-gutters { background: var(--surface-2); border-right: 1px solid var(--border); }
.CodeMirror-linenumber { color: var(--muted); }
.CodeMirror-cursor { border-left-color: var(--text); }
.CodeMirror-selected, .CodeMirror-focused .CodeMirror-selected { background: color-mix(in srgb, var(--accent) 28%, transparent); }
.cm-s-default .cm-keyword { color: var(--kw); }
.cm-s-default .cm-string { color: var(--str); }
.cm-s-default .cm-number { color: var(--num); }
.cm-s-default .cm-comment { color: var(--com); font-style: italic; }
.cm-s-default .cm-def { color: var(--def); }
.cm-s-default .cm-builtin { color: var(--def); }
.cm-s-default .cm-variable, .cm-s-default .cm-variable-2, .cm-s-default .cm-property, .cm-s-default .cm-operator { color: var(--text); }

.toolbar { display: flex; gap: 8px; align-items: center; padding: 10px 16px; }
.spacer { flex: 1 1 auto; }
button {
  font: inherit; color: var(--text); background: var(--surface);
  border: 1px solid var(--border); border-radius: 6px; padding: 6px 14px; cursor: pointer;
}
button:hover:not(:disabled) { border-color: var(--accent); }
button:disabled { opacity: 0.55; cursor: default; }
button.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-text); font-weight: 600; }
button.quiet { background: none; border-color: transparent; color: var(--muted); }

.results { flex: 1 1 45%; min-height: 140px; overflow: auto; padding: 4px 16px 16px; }
.hint { color: var(--muted); margin: 6px 0; }
.summary { font-weight: 650; padding: 8px 12px; border-radius: 6px; margin: 4px 0 10px; background: var(--surface-2); }
.summary.pass { color: var(--pass); background: var(--pass-bg); }
.summary.fail { color: var(--fail); background: var(--fail-bg); }
.tests { list-style: none; margin: 0; padding: 0; }
.test { padding: 6px 0; border-bottom: 1px solid var(--border); }
.test-head { display: flex; gap: 8px; align-items: baseline; }
.test .mark { font-weight: 700; width: 1em; }
.test.passed .mark { color: var(--pass); }
.test.failed .mark, .test.error .mark { color: var(--fail); }
.test.passed .name { color: var(--muted); }
.tag { font-size: 12px; color: var(--fail); border: 1px solid var(--fail); border-radius: 4px; padding: 0 5px; }
.message, .output {
  font: 13px/1.5 var(--mono); white-space: pre-wrap; overflow-wrap: anywhere;
  margin: 6px 0 2px 1.5em; padding: 8px 10px;
  background: var(--surface); border: 1px solid var(--border); border-radius: 6px;
}
.output { margin-left: 0; }
.output.error { border-color: var(--fail); }
.label { font-size: 13px; font-weight: 650; color: var(--muted); margin: 12px 0 4px; }
.label.fail { color: var(--fail); }
.figure { display: block; max-width: 100%; margin: 8px 0; background: #ffffff; border: 1px solid var(--border); border-radius: 6px; }

.written { padding: 12px 16px 16px; border-top: 1px solid var(--border); background: var(--surface); }
.written label { display: block; font-weight: 600; margin-bottom: 6px; }
.written textarea {
  width: 100%; font: 15px/1.5 var(--sans); color: var(--text);
  background: var(--bg); border: 1px solid var(--border); border-radius: 6px; padding: 8px 10px; resize: vertical;
}
.written-foot { display: flex; justify-content: space-between; gap: 12px; font-size: 12.5px; color: var(--muted); margin-top: 4px; }
#written-count[data-over="true"] { color: var(--fail); font-weight: 600; }

.fatal { margin: 24px; padding: 12px 16px; color: var(--fail); background: var(--fail-bg); border-radius: 6px; }

/* ---------- self-test ---------- */

.selftest { padding: 20px 24px 48px; overflow: auto; }
.selftest h1 { font-size: 22px; margin: 0 0 8px; }
.selftest-table { border-collapse: collapse; font-size: 13.5px; width: 100%; }
.selftest-table th, .selftest-table td { border-bottom: 1px solid var(--border); padding: 4px 10px; text-align: left; vertical-align: top; }
.selftest-table tr.bad td { color: var(--fail); background: var(--fail-bg); }
.selftest-table td:last-child { overflow-wrap: anywhere; }

/* ---------- narrow screens ---------- */

@media (max-width: 900px) {
  html, body { height: auto; }
  .topbar { flex-wrap: wrap; gap: 8px 12px; }
  .picker { order: 3; flex-basis: 100%; }
  .layout { display: block; overflow: visible; }
  .work { overflow-y: visible; }
  .docs { border-right: 0; border-bottom: 1px solid var(--border); }
  .doc { padding: 16px 16px 32px; overflow: visible; }
  .editor { height: 360px; flex: none; }
  .results { overflow: visible; }
}

/* ---------- print: the reading only ---------- */

@media print {
  html, body { height: auto; background: #ffffff; color: #000000; }
  .topbar, .tabs, .work, .selftest { display: none !important; }
  .layout { display: block; }
  .docs { border: 0; }
  .doc { overflow: visible; padding: 0; }
  .doc > div { font-size: 11pt; max-width: none; }
  .doc pre, .doc blockquote, .doc details, .doc table, .doc img { break-inside: avoid; }
  .doc details { border: 1px solid #999999; background: none; }
}

/* ---------- invited-group accounts and progress ---------- */
[hidden] { display: none !important; }
.account-nav { display: flex; flex-wrap: wrap; gap: 6px; }
.account-nav button { font-size: 12.5px; padding: 5px 8px; }
.account-status { padding: 6px 16px; font-size: 13px; background: var(--surface-2); color: var(--muted); }
.notice { padding: 10px 16px; background: var(--note-bg); border-bottom: 1px solid var(--note-border); }
.notice.error { color: var(--fail); background: var(--fail-bg); border-color: var(--fail); }
.account-panel, .dashboard { flex: 1 1 auto; overflow: auto; padding: 28px max(20px, calc((100% - 1100px) / 2)); }
.account-panel { width: min(100%, 560px); margin: 0 auto; padding: 32px 24px; }
.account-panel h1, .dashboard h1 { font-size: 26px; line-height: 1.25; margin: 0 0 16px; }
.account-panel form { display: grid; gap: 8px; }
.account-panel form > label { margin-top: 8px; font-weight: 600; }
input:not([type="checkbox"]), .review-tools textarea {
  width: 100%; font: inherit; color: var(--text); background: var(--surface);
  border: 1px solid var(--border); border-radius: 6px; padding: 8px 10px;
}
input:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
input[type="checkbox"] { accent-color: var(--accent); }
.form-error, .error-text { color: var(--fail); }
.form-error { margin: 8px 0; }
.button-row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; margin-top: 10px; }
.section-head { display: flex; justify-content: space-between; align-items: baseline; gap: 16px; }
.question-path section { margin: 24px 0; }
.question-path h2 { font-size: 18px; }
.question-list { display: grid; grid-template-columns: repeat(auto-fit, minmax(270px, 1fr)); gap: 8px; }
.question-card { text-align: left; display: flex; align-items: baseline; gap: 10px; width: 100%; padding: 12px; }
.question-card .question-name { flex: 1; }
.question-card .question-code { color: var(--accent); font-weight: 650; }
.question-card .question-status { font-size: 12px; color: var(--muted); white-space: nowrap; }
.question-card.complete { border-left: 3px solid var(--pass); }
.question-card:disabled { opacity: .65; }
.usage-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(170px, 1fr)); gap: 12px; margin: 16px 0; }
.usage-card { background: var(--surface); padding: 14px; border: 1px solid var(--border); border-radius: 6px; }
.usage-card strong { display: block; font-size: 21px; }
.usage-card span { color: var(--muted); font-size: 13px; }
.admin-create { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 18px; margin: 24px 0; }
.admin-create h2 { margin-top: 0; font-size: 19px; }
.account-grid { display: grid; grid-template-columns: 1fr 1.3fr .8fr auto; align-items: start; gap: 12px; }
.account-grid label { display: grid; gap: 5px; font-weight: 600; }
.account-grid small { font-weight: 400; color: var(--muted); }
.account-grid > button { margin-top: 27px; }
.admin-account { margin: 10px 0; padding: 14px; border: 1px solid var(--border); border-radius: 6px; background: var(--surface); }
.admin-account summary { cursor: pointer; font-weight: 600; }
.admin-account summary span { margin-left: 12px; font-size: 13px; font-weight: 400; color: var(--muted); }
.admin-account .account-grid { margin-top: 16px; grid-template-columns: 1fr 1.3fr 1fr auto; }
.admin-account .check-label { display: flex; align-items: center; gap: 8px; padding-top: 30px; }
.admin-account .check-label input { width: auto; }
.review-tools { padding: 16px; border-top: 1px solid var(--border); background: var(--surface); }
.review-tools > label { display: block; margin: 8px 0 5px; }
.review-tools .reading-check { display: flex; align-items: flex-start; gap: 8px; margin-bottom: 18px; }
.review-tools textarea { resize: vertical; }
.feedback { margin-top: 16px; }
.feedback h2 { font-size: 18px; margin-bottom: 6px; }
.feedback h3 { font-size: 15px; margin-bottom: 4px; }
.feedback ul { padding-left: 22px; }
.feedback li { margin-bottom: 8px; }
.feedback pre { max-height: 500px; overflow: auto; font: 13px/1.5 var(--mono); background: var(--code-bg); padding: 14px; white-space: pre; }
.feedback .review-scores { display: grid; grid-template-columns: 1fr auto; gap: 5px 16px; margin: 12px 0; font-size: 13px; }
.feedback .review-scores dt, .feedback .review-scores dd { margin: 0; }
.work-head { flex-wrap: wrap; gap: 5px 8px; }
#draft-state[data-kind="error"] { color: var(--fail); }
#draft-state[data-kind="saving"] { color: var(--muted); }
@media (max-width: 1200px) {
  .topbar { flex-wrap: wrap; gap: 8px 12px; }
  .account-nav { margin-left: auto; }
  .account-grid, .admin-account .account-grid { grid-template-columns: 1fr 1fr; }
  .account-grid > button { margin-top: 0; align-self: end; }
}
@media (max-width: 600px) {
  .brand { font-size: 14px; }
  .engine-status { font-size: 12px; }
  .account-nav { width: 100%; margin: 0; }
  .account-panel, .dashboard { padding: 20px 16px; }
  .account-grid, .admin-account .account-grid { grid-template-columns: 1fr; }
  .admin-account .check-label { padding-top: 0; }
  .admin-account summary span { display: block; margin-left: 0; }
  .toolbar { flex-wrap: wrap; }
}
@media print {
  .account-nav, .account-status, .notice, .account-panel, .dashboard, .review-tools { display: none !important; }
}

/* Account feedback can exceed the viewport: keep the complete work pane reachable. */
.work { overflow-y: auto; }
.work > * { flex-shrink: 0; }
.work .editor { min-height: 260px; }
/* Administrator account creation and permanent deletion. */
.created-credentials { margin-top: 1rem; padding: 1rem; border: 1px solid #779b82; border-radius: 6px; }
.created-credentials input { display: block; width: min(100%, 32rem); margin: .5rem 0; font-family: monospace; }
.delete-account { margin-top: 1rem; padding-top: 1rem; border-top: 1px solid #d3a3a3; }
.delete-account > summary { color: #9b2828; cursor: pointer; }
button.danger { color: #fff; background: #a42b2b; border-color: #a42b2b; }
button.danger:disabled { opacity: .5; }