/* ============ design tokens ============ */
:root {
  --bg: #f6f6f4;
  --panel: #ffffff;
  --panel-2: #fbfbf9;
  --text: #1c1f24;
  --muted: #6b7076;
  --border: #e3e4e1;
  --accent: #2f5ee0;
  --accent-hover: #254fc4;
  --accent-soft: #e8edfb;
  --ok: #1a7f4e;
  --ok-soft: #e3f3ea;
  --err: #c0392b;
  --err-soft: #fbeae7;
  --shadow: 0 1px 2px rgba(20, 24, 30, .06), 0 8px 24px rgba(20, 24, 30, .08);
  --radius: 10px;
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
}

html[data-theme="dark"] {
  --bg: #141619;
  --panel: #1c1f24;
  --panel-2: #20242a;
  --text: #e8eaed;
  --muted: #9aa0a8;
  --border: #2e333a;
  --accent: #6b8cff;
  --accent-hover: #82a0ff;
  --accent-soft: #26304d;
  --ok: #3ddc84;
  --ok-soft: #173a28;
  --err: #ff7a6b;
  --err-soft: #45221e;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 8px 24px rgba(0, 0, 0, .5);
}

* { box-sizing: border-box; margin: 0; padding: 0; }

/* the `hidden` attribute must always win over display rules like .screen/.modal-overlay */
[hidden] { display: none !important; }

html, body { height: 100%; }

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
}

button { font: inherit; cursor: pointer; }
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }
code { font-size: .92em; background: var(--panel-2); border: 1px solid var(--border); border-radius: 5px; padding: 1px 5px; }

.screen { min-height: 100vh; display: flex; flex-direction: column; }

/* ============ shared buttons ============ */
.btn {
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  padding: 9px 18px;
  border-radius: 8px;
  font-weight: 600;
  transition: background .12s, border-color .12s, transform .05s;
}
.btn:hover { background: var(--panel-2); }
.btn:active { transform: translateY(1px); }
.btn:disabled { opacity: .45; cursor: default; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: #fff; }
.btn.primary:hover { background: var(--accent-hover); }
.btn.small { padding: 4px 12px; font-size: 13px; border-radius: 6px; }

.icon-btn {
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  width: 38px; height: 38px;
  border-radius: 8px;
  font-size: 17px;
  line-height: 1;
  display: inline-flex; align-items: center; justify-content: center;
  transition: background .12s;
}
.icon-btn:hover { background: var(--panel-2); }
.icon-btn.active { background: var(--accent-soft); border-color: var(--accent); }

/* ============ home ============ */
.home-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 18px 28px; border-bottom: 1px solid var(--border);
  background: var(--panel);
  position: sticky; top: 0; z-index: 30;
}
.home-brand { display: flex; align-items: center; gap: 12px; }
.brand-badge {
  background: var(--accent); color: #fff;
  font-weight: 800; letter-spacing: .08em;
  padding: 5px 10px; border-radius: 7px; font-size: 14px;
}
.brand-badge.small { padding: 3px 7px; font-size: 12px; }
.brand-name { font-weight: 700; font-size: 19px; }
.home-actions { display: flex; gap: 8px; }

.home-main { max-width: 900px; margin: 0 auto; padding: 40px 24px 70px; width: 100%; }
.home-hero { text-align: center; margin-bottom: 34px; }
.home-hero h1 { font-size: 30px; font-weight: 800; letter-spacing: -.02em; margin-bottom: 12px; }
.home-hero sup { font-size: .5em; color: var(--muted); font-weight: 400; }
.hero-sub { color: var(--muted); max-width: 640px; margin: 0 auto; font-size: 15.5px; }

.setup-card {
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 26px 28px;
}
.setup-section { margin-bottom: 22px; }
.setup-label {
  font-size: 13px; font-weight: 700; text-transform: uppercase; letter-spacing: .06em;
  color: var(--muted); margin-bottom: 9px;
}
.seg { display: flex; flex-wrap: wrap; gap: 8px; }
.seg-btn {
  border: 1px solid var(--border);
  background: var(--panel-2);
  color: var(--text);
  padding: 9px 18px; border-radius: 8px; font-weight: 600; font-size: 14.5px;
  transition: all .12s;
}
.seg-btn:hover { border-color: var(--accent); }
.seg-btn.active { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }

.setup-footer {
  display: flex; align-items: center; justify-content: space-between; gap: 14px;
  border-top: 1px solid var(--border); padding-top: 20px; flex-wrap: wrap;
}
.avail-count { color: var(--muted); font-size: 14px; }

.home-resources { margin-top: 44px; }
.home-resources h2, .results-section h2 { font-size: 17px; font-weight: 700; margin-bottom: 14px; }
.resource-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; }
.resource-card {
  display: flex; flex-direction: column; gap: 4px;
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; color: var(--text);
  transition: border-color .12s, transform .12s;
}
.resource-card:hover { border-color: var(--accent); text-decoration: none; transform: translateY(-1px); }
.resource-title { font-weight: 700; font-size: 15px; }
.resource-desc { color: var(--muted); font-size: 13.5px; }
.provenance { color: var(--muted); font-size: 12.5px; margin-top: 22px; line-height: 1.6; }

/* ============ practice (test) layout ============ */
.test-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 12px 20px; border-bottom: 1px solid var(--border);
  background: var(--panel); position: sticky; top: 0; z-index: 30;
}
.th-left { display: flex; align-items: center; gap: 10px; min-width: 180px; }
.th-section { font-weight: 700; font-size: 15px; }
.th-center { text-align: center; }
.th-right { display: flex; gap: 8px; min-width: 180px; justify-content: flex-end; }

.timer { font-variant-numeric: tabular-nums; font-weight: 700; font-size: 21px; letter-spacing: .02em; }
.timer.warn { color: var(--err); }
.timer-sub { display: block; font-size: 11px; color: var(--muted); }

.prefs-pop {
  position: fixed; top: 64px; right: 20px; z-index: 60;
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 16px; width: 260px;
}
.pref-row { display: flex; align-items: center; justify-content: space-between; padding: 7px 0; font-size: 14.5px; }
.pref-row.note { color: var(--muted); font-size: 12.5px; border-top: 1px solid var(--border); margin-top: 8px; padding-top: 10px; }

.test-main {
  flex: 1;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
  gap: 0;
  max-width: 1200px; width: 100%; margin: 0 auto;
}
@media (max-width: 860px) { .test-main { grid-template-columns: 1fr; } }

.question-col {
  padding: 30px 34px 40px;
  border-right: 1px solid var(--border);
  overflow-y: auto;
}
@media (max-width: 860px) { .question-col { border-right: none; border-bottom: 1px solid var(--border); } }

.q-head {
  display: flex; justify-content: space-between; align-items: baseline; gap: 12px;
  margin-bottom: 20px; flex-wrap: wrap;
}
#q-count { font-size: 13px; font-weight: 700; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; }
.q-skill { font-size: 12.5px; color: var(--muted); background: var(--panel-2); border: 1px solid var(--border); padding: 3px 10px; border-radius: 20px; }

.q-stimulus { margin-bottom: 18px; }
.q-stimulus p { margin-bottom: 12px; }
.q-stem { font-size: 17px; }
.q-stem p { margin-bottom: 12px; }
.q-stem .choice_paragraph, .q-stimulus .choice_paragraph { margin-bottom: 6px; }

/* math rendering (MathJax output + legacy base64 images) */
.q-stem img, .q-stimulus img, .q-rationale img, .choice-body img { max-width: 100%; vertical-align: middle; }
.q-stem mjx-container, .q-stimulus mjx-container, .q-rationale mjx-container, .choice-body mjx-container { margin: 2px 1px; }

.spr-label { font-size: 13px; font-weight: 700; color: var(--muted); margin: 18px 0 6px; text-transform: uppercase; letter-spacing: .05em; }
.spr-input {
  width: 200px; padding: 11px 14px; font-size: 18px; font-weight: 600;
  border: 1.5px solid var(--border); border-radius: 8px; background: var(--panel);
  color: var(--text); font-variant-numeric: tabular-nums;
}
.spr-input:focus { outline: none; border-color: var(--accent); }
.spr-hint { color: var(--muted); font-size: 13px; margin-top: 7px; }

.q-rationale {
  margin-top: 24px; border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px; background: var(--panel-2); font-size: 15px;
}
.q-rationale.ok { border-color: var(--ok); background: var(--ok-soft); }
.q-rationale.err { border-color: var(--err); background: var(--err-soft); }
.q-rationale h3 { font-size: 14px; margin-bottom: 8px; text-transform: uppercase; letter-spacing: .05em; }
.q-rationale.ok h3 { color: var(--ok); }
.q-rationale.err h3 { color: var(--err); }
.q-rationale p { margin-bottom: 10px; }
.q-rationale .ka-link { display: inline-block; margin-top: 6px; }

.q-resources { margin-top: 18px; font-size: 14px; color: var(--muted); }

.choices-col { padding: 30px 34px 40px; display: flex; flex-direction: column; }
.choice {
  display: flex; gap: 14px; align-items: flex-start;
  border: 1.5px solid var(--border); border-radius: 10px;
  padding: 14px 16px; margin-bottom: 12px; cursor: pointer;
  background: var(--panel); transition: border-color .12s, background .12s;
}
.choice:hover { border-color: var(--accent); }
.choice .letter {
  flex: 0 0 30px; height: 30px; border-radius: 50%;
  border: 1.5px solid var(--border); display: flex; align-items: center; justify-content: center;
  font-weight: 700; font-size: 14px; color: var(--muted); margin-top: 2px;
}
.choice .choice-body { flex: 1; font-size: 16px; }
.choice.selected { border-color: var(--accent); background: var(--accent-soft); }
.choice.selected .letter { border-color: var(--accent); background: var(--accent); color: #fff; }
.choice.correct { border-color: var(--ok); background: var(--ok-soft); }
.choice.correct .letter { border-color: var(--ok); background: var(--ok); color: #fff; }
.choice.wrong { border-color: var(--err); background: var(--err-soft); }
.choice.wrong .letter { border-color: var(--err); background: var(--err); color: #fff; }
.choice.dim { opacity: .5; }
.choice.correct-mark { margin-left: 4px; color: var(--ok); font-weight: 700; }

.check-btn { margin-top: 8px; align-self: flex-start; padding: 12px 26px; }

.test-footer {
  display: flex; align-items: center; justify-content: space-between; gap: 16px;
  border-top: 1px solid var(--border); background: var(--panel);
  padding: 14px 20px; position: sticky; bottom: 0; z-index: 30;
  flex-wrap: wrap;
}
.tf-left { display: flex; align-items: center; gap: 18px; flex-wrap: wrap; }
.mark-label { display: flex; align-items: center; gap: 7px; font-size: 14px; cursor: pointer; color: var(--muted); }
.mark-label input { width: 16px; height: 16px; accent-color: var(--accent); cursor: pointer; }
.nav-grid { display: flex; flex-wrap: wrap; gap: 5px; }
.nav-dot {
  width: 30px; height: 30px; border-radius: 7px;
  border: 1px solid var(--border); background: var(--panel-2);
  font-size: 12.5px; font-weight: 600; color: var(--muted);
  display: flex; align-items: center; justify-content: center;
}
.nav-dot.current { border-color: var(--accent); color: var(--accent); background: var(--accent-soft); }
.nav-dot.answered { background: var(--accent); border-color: var(--accent); color: #fff; }
.nav-dot.correct { background: var(--ok); border-color: var(--ok); color: #fff; }
.nav-dot.wrong { background: var(--err); border-color: var(--err); color: #fff; }
.nav-dot.flagged::after { content: "⚑"; font-size: 10px; position: absolute; }
.nav-dot { position: relative; }
.tf-right { display: flex; gap: 10px; }

/* ============ results ============ */
.results-main { max-width: 900px; margin: 0 auto; padding: 44px 24px 80px; width: 100%; }
.results-hero { text-align: center; margin-bottom: 40px; }
.score-ring {
  width: 150px; height: 150px; border-radius: 50%;
  border: 8px solid var(--accent); margin: 0 auto 22px;
  display: flex; flex-direction: column; align-items: center; justify-content: center;
  background: var(--panel);
}
.score-num { font-size: 34px; font-weight: 800; letter-spacing: -.02em; }
.score-sub { color: var(--muted); font-size: 13.5px; }
.results-hero h1 { font-size: 26px; font-weight: 800; margin-bottom: 8px; }
.results-actions { display: flex; gap: 12px; justify-content: center; margin-top: 20px; }

.review-list { display: flex; flex-direction: column; gap: 10px; }
.review-item {
  display: flex; align-items: center; gap: 14px;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--panel); padding: 13px 16px;
}
.review-status { font-size: 18px; flex: 0 0 28px; text-align: center; }
.review-text { flex: 1; min-width: 0; }
.review-q { font-size: 14.5px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
.review-meta { font-size: 12.5px; color: var(--muted); }
.review-actions { display: flex; gap: 8px; }

/* ============ modals ============ */
.modal-overlay {
  position: fixed; inset: 0; z-index: 100;
  background: rgba(15, 18, 24, .55);
  display: flex; align-items: center; justify-content: center; padding: 20px;
  backdrop-filter: blur(2px);
}
.modal {
  background: var(--panel); border-radius: 12px; box-shadow: var(--shadow);
  display: flex; flex-direction: column; max-height: 92vh; overflow: hidden;
}
.modal-head { display: flex; align-items: center; justify-content: space-between; padding: 12px 16px; border-bottom: 1px solid var(--border); }
.modal-title { font-weight: 700; font-size: 15px; }

.calc-modal { width: min(880px, 96vw); }
.calc-tabs { display: flex; gap: 6px; }
.calc-tab {
  border: 1px solid var(--border); background: var(--panel-2); color: var(--muted);
  padding: 7px 16px; border-radius: 7px; font-size: 14px; font-weight: 600;
}
.calc-tab.active { background: var(--accent-soft); border-color: var(--accent); color: var(--accent); }
.calc-body { height: 62vh; min-height: 380px; }
.calc-body .dcg-wrapper { border-radius: 0 0 12px 12px; }

.ref-modal { width: min(720px, 96vw); }
.ref-body { padding: 20px 26px; overflow-y: auto; }
.ref-body table { width: 100%; border-collapse: collapse; font-size: 14.5px; }
.ref-body td { padding: 8px 6px; border-bottom: 1px solid var(--border); vertical-align: top; }
.ref-body td:first-child { width: 45%; font-family: Georgia, "Times New Roman", serif; }
.ref-body h4 { margin: 18px 0 8px; font-size: 13px; text-transform: uppercase; letter-spacing: .05em; color: var(--muted); }

/* ============ top nav ============ */
.topnav {
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 10px 20px; border-bottom: 1px solid var(--border);
  background: var(--panel); position: sticky; top: 0; z-index: 50;
}
body.immersive .topnav { display: none; }  /* hidden during active practice/test sessions */
.nav-brand {
  border: none; background: none; display: flex; align-items: center; gap: 7px;
  font-weight: 800; font-size: 18px; color: var(--text); padding: 4px 6px; border-radius: 7px;
}
.nav-brand:hover { background: var(--panel-2); }
.nav-brand span { color: var(--accent); }
.nav-tabs { display: flex; gap: 4px; }
.nav-tab {
  border: none; background: none; color: var(--muted);
  font-weight: 600; font-size: 14.5px; padding: 7px 13px; border-radius: 8px;
}
.nav-tab:hover { background: var(--panel-2); color: var(--text); }
.nav-tab.active { background: var(--accent-soft); color: var(--accent); }
.nav-actions { display: flex; gap: 8px; align-items: center; }

/* ============ page shells ============ */
.page-main { max-width: 980px; margin: 0 auto; padding: 34px 24px 80px; width: 100%; }
.page-main.narrow { max-width: 680px; }
.page-main.center { text-align: center; }
.screen-title { font-size: 26px; font-weight: 800; letter-spacing: -.02em; margin-bottom: 8px; }
.screen-title + .hero-sub { margin-bottom: 26px; }

/* ============ dashboard ============ */
.stat-row { display: grid; grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); gap: 12px; margin: 0 auto 30px; max-width: 780px; }
.stat-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 18px 20px; text-align: center; box-shadow: var(--shadow);
}
.stat-num { font-size: 26px; font-weight: 800; letter-spacing: -.02em; }
.stat-num.small { font-size: 21px; }
.stat-label { font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: .06em; font-weight: 700; margin-top: 3px; }

.action-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 12px; margin-bottom: 44px; }
.action-card {
  display: flex; flex-direction: column; gap: 5px; text-align: left;
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 22px; color: var(--text); box-shadow: var(--shadow);
  transition: border-color .12s, transform .12s;
}
.action-card:hover { border-color: var(--accent); transform: translateY(-2px); }
.action-card.primary { border-top: 3px solid var(--accent); }
.action-icon { font-size: 22px; }
.action-title { font-weight: 800; font-size: 16px; }
.action-desc { color: var(--muted); font-size: 13.5px; }

/* ============ full test ============ */
.test-spec {
  background: var(--panel-2); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 20px; font-size: 14.5px; line-height: 1.9; margin-bottom: 6px;
}
.test-spec b { color: var(--accent); }
.th-module { font-size: 12.5px; color: var(--muted); background: var(--panel-2); border: 1px solid var(--border); padding: 3px 10px; border-radius: 20px; }

.break-card {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  box-shadow: var(--shadow); padding: 44px 40px; max-width: 520px; margin: 40px auto;
}
.break-card h1 { font-size: 24px; font-weight: 800; margin-bottom: 10px; }
.break-timer {
  font-size: 44px; font-weight: 800; font-variant-numeric: tabular-nums;
  color: var(--accent); margin: 22px 0 8px; letter-spacing: .02em;
}

.score-big { margin-bottom: 18px; }
.score-big-num { font-size: 52px; font-weight: 800; letter-spacing: -.02em; line-height: 1.05; }
.section-scores { display: flex; gap: 12px; justify-content: center; margin-top: 22px; flex-wrap: wrap; }
.section-score {
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 22px; min-width: 170px; box-shadow: var(--shadow);
}
.section-score .ss-num { font-size: 30px; font-weight: 800; }
.section-score .ss-label { font-size: 12px; color: var(--muted); text-transform: uppercase; letter-spacing: .05em; font-weight: 700; margin-top: 2px; }
.section-score .ss-raw { font-size: 12.5px; color: var(--muted); }

/* ============ question bank ============ */
.bank-toolbar {
  display: flex; flex-wrap: wrap; gap: 10px; align-items: center;
  background: var(--panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px; margin: 20px 0 14px;
}
.select, .search-input {
  border: 1px solid var(--border); background: var(--panel-2); color: var(--text);
  padding: 9px 12px; border-radius: 8px; font: inherit; font-size: 14px;
}
.select:focus, .search-input:focus { outline: none; border-color: var(--accent); }
.search-input { flex: 1; min-width: 180px; }
.bank-count { color: var(--muted); font-size: 13.5px; margin-bottom: 12px; }
.bank-list { display: flex; flex-direction: column; gap: 9px; }
.bank-item {
  display: flex; align-items: center; gap: 12px;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--panel); padding: 12px 16px;
}
.bank-item .bank-status { font-size: 16px; flex: 0 0 24px; text-align: center; }
.bank-item .bank-text { flex: 1; min-width: 0; }
.bank-item .bank-q {
  font-size: 14.5px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; display: block;
}
.bank-item .bank-meta { font-size: 12.5px; color: var(--muted); display: block; margin-top: 2px; }
.bank-item .bank-actions { display: flex; gap: 7px; }
.bank-pager { display: flex; align-items: center; justify-content: center; gap: 16px; margin-top: 20px; }
.bank-pager span { color: var(--muted); font-size: 14px; }

.bank-modal { width: min(880px, 96vw); }
.bank-viewer { padding: 22px 28px 28px; overflow-y: auto; }
.bank-viewer .q-head { margin-bottom: 16px; }
.bank-viewer .choice { cursor: default; }
.bank-viewer .choice.selected { border-color: var(--border); background: var(--panel); }
.bank-viewer .choice.selected .letter { border-color: var(--border); background: var(--panel-2); color: var(--muted); }
.bank-viewer .choice.reveal-correct { border-color: var(--ok); background: var(--ok-soft); }
.bank-viewer .choice.reveal-correct .letter { border-color: var(--ok); background: var(--ok); color: #fff; }
.bank-viewer .q-rationale { margin-top: 20px; }
.bank-viewer .bm-actions { display: flex; gap: 10px; margin-top: 18px; flex-wrap: wrap; }

/* ============ stats / skill mastery ============ */
.skill-list { display: flex; flex-direction: column; gap: 10px; }
.skill-item {
  display: flex; align-items: center; gap: 14px;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--panel); padding: 12px 16px;
}
.skill-name { flex: 0 0 240px; font-size: 14px; font-weight: 600; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
@media (max-width: 700px) { .skill-name { flex-basis: 100%; } .skill-item { flex-wrap: wrap; } }
.skill-bar { flex: 1; height: 9px; border-radius: 6px; background: var(--panel-2); border: 1px solid var(--border); overflow: hidden; min-width: 80px; }
.skill-bar i { display: block; height: 100%; background: var(--accent); border-radius: 6px; }
.skill-num { font-size: 13.5px; font-weight: 700; width: 120px; text-align: right; color: var(--muted); font-variant-numeric: tabular-nums; }
.skill-item a { font-size: 12.5px; }

/* ============ responsive ============ */
@media (max-width: 700px) {
  .home-main { padding: 26px 16px 50px; }
  .home-hero h1 { font-size: 24px; }
  .setup-card { padding: 20px 18px; }
  .question-col, .choices-col { padding: 22px 20px 30px; }
  .th-section { display: none; }
  .timer { font-size: 17px; }
  .topnav { padding: 8px 12px; flex-wrap: wrap; }
  .nav-tab { font-size: 13px; padding: 6px 9px; }
  .nav-brand span { display: none; }
  .page-main { padding: 22px 14px 60px; }
  .break-card { padding: 30px 22px; }
  .bank-toolbar { padding: 12px; }
  .bank-item .bank-q { white-space: normal; }
}