:root { --ink:#202326; --muted:#61666c; --line:#e5e7ea; --soft:#f5f6f8; --paper:#fff; --focus:#245de1; font-family:Arial,Helvetica,sans-serif; color:var(--ink); background:var(--paper); font-synthesis:none; }
* { box-sizing:border-box; }
body { margin:0; line-height:1.6; }
[hidden] { display:none!important; }
a { color:inherit; text-underline-offset:4px; }
button,input,select,textarea { font:inherit; }
button,a,input,select,textarea { -webkit-tap-highlight-color:transparent; }
button,select { touch-action:manipulation; }
button { cursor:pointer; background:var(--paper); color:var(--ink); border:1px solid #afb5bc; border-radius:6px; padding:10px 15px; min-height:44px; }
button:hover { background:var(--soft); }
button:disabled { opacity:.45; cursor:default; }
button.primary { color:#fff; background:var(--ink); border-color:var(--ink); }
button.primary:hover { background:#3d4247; }
:focus-visible { outline:3px solid var(--focus); outline-offset:4px; }
.skip { position:fixed; top:10px; left:10px; z-index:10; padding:10px; background:var(--paper); transform:translateY(-200%); }
.skip:focus { transform:none; }
.site-header { max-width:1180px; margin:auto; padding:22px 32px; display:flex; justify-content:space-between; align-items:center; border-bottom:1px solid var(--line); gap:24px; }
.brand { font-weight:700; text-decoration:none; white-space:nowrap; }
.site-header nav { display:flex; gap:22px; flex-wrap:wrap; font-size:.88rem; }
.site-header nav a { text-decoration:none; min-height:44px; display:flex; align-items:center; }
main { max-width:1180px; margin:auto; padding:0 32px 42px; }
.hero { display:flex; align-items:center; justify-content:space-between; gap:25px; padding:44px 0 26px; }
.hero>div { max-width:690px; }
.eyebrow { color:var(--muted); font-size:.73rem; letter-spacing:.09em; font-weight:600; margin:0 0 10px; }
.beta { border:1px solid var(--line); border-radius:4px; padding:3px 6px; margin-left:5px; font-weight:400; letter-spacing:0; }
h1 { font-size:clamp(2.1rem,5vw,3.35rem); line-height:1.15; letter-spacing:-.045em; margin:12px 0 20px; font-weight:650; }
h2 { font-size:1.3rem; line-height:1.4; margin:0; letter-spacing:-.02em; }
h3 { font-size:1.1rem; margin:0 0 16px; }
p { margin:0 0 14px; }
.intro { font-size:1.25rem; line-height:1.45; margin-bottom:15px; }
.hero-sprite { object-fit:contain; max-width:25%; height:auto; max-height:185px; }
.muted { color:var(--muted); }
.small { font-size:.84rem; }
.bank-summary { border-block:1px solid var(--line); padding:18px 0; display:flex; justify-content:space-between; gap:12px; font-size:.89rem; margin:0 0 35px; }
.bank-summary span { color:var(--muted); }
.practice-modes { display:flex; flex-wrap:wrap; gap:10px; margin:0 0 30px; padding-bottom:22px; border-bottom:1px solid var(--line); }
.practice-modes button { font-weight:600; }
.practice-modes button[aria-pressed="true"] { color:var(--paper); background:var(--ink); border-color:var(--ink); }
.practice-modes button[aria-pressed="true"]:hover { background:#3d4247; }
.section-top { display:flex; justify-content:space-between; align-items:center; gap:18px; margin-bottom:14px; }
.section-top>a { font-size:.82rem; flex-shrink:0; }
.filters { display:grid; grid-template-columns:1.5fr 1fr; gap:18px; padding:18px 0; }
.diagram-choice { display:flex; align-items:center; gap:10px; min-height:44px; font-weight:400; }
.diagram-choice input { width:20px; height:20px; accent-color:var(--ink); }
.solution .diagram { margin-bottom:0; }
.browse-search { margin:22px 0 16px; }
.browse-search input { display:block; width:100%; min-height:48px; margin-top:7px; padding:11px 13px; border:1px solid #9299a1; border-radius:5px; background:var(--paper); color:var(--ink); font-weight:400; }
.browse-search input::placeholder { color:var(--muted); opacity:1; }
.browse-filters { display:grid; grid-template-columns:1.2fr 1.35fr 1.2fr 1fr .85fr; gap:16px; padding-bottom:24px; border-bottom:1px solid var(--line); }
.browse-filters label { min-width:0; }
.browser-workspace { display:grid; grid-template-columns:330px minmax(0,1fr); gap:30px; align-items:start; margin-top:26px; }
.browser-results,.browser-detail,.browse-preview { min-width:0; }
.browser-results-heading { display:flex; flex-wrap:wrap; align-items:baseline; justify-content:space-between; gap:6px 12px; margin-bottom:12px; }
.browser-results-heading h3 { margin:0; font-size:1rem; }
#browse-results-status { margin:0; color:var(--muted); font-size:.76rem; }
.browse-list { list-style:none; padding:0; margin:0; border-top:1px solid var(--line); max-height:680px; overflow-y:auto; scroll-padding:12px; }
.browse-item { display:flex; align-items:flex-start; gap:8px; border-bottom:1px solid var(--line); padding-right:8px; }
.browse-list li[data-active="true"] { background:var(--soft); box-shadow:inset 3px 0 var(--ink); }
.browse-list button[data-preview] { display:flex; flex:1; flex-direction:column; align-items:flex-start; gap:5px; min-width:0; padding:15px 10px 15px 13px; border:0; border-radius:0; text-align:left; background:transparent; overflow-wrap:anywhere; }
.browse-list button[data-preview]:hover { background:var(--soft); }
.browse-result-title { font-size:.89rem; font-weight:600; line-height:1.45; }
.browse-result-meta { font-size:.72rem; color:var(--muted); line-height:1.6; }
.browse-snippet { font-size:.8rem; line-height:1.6; display:-webkit-box; -webkit-box-orient:vertical; -webkit-line-clamp:2; overflow:hidden; }
.browse-snippet .katex { font-size:1em; }
.browse-reference { color:var(--muted); font-size:.68rem; letter-spacing:.02em; }
.browse-list button[data-select] { flex-shrink:0; min-width:58px; margin-top:14px; padding:8px 9px; font-size:.76rem; }
.browse-list button[data-select][aria-pressed="true"],.browse-preview button[data-select][aria-pressed="true"] { border-color:var(--ink); background:var(--ink); color:var(--paper); }
.browse-empty { padding:22px 0; font-size:.89rem; color:var(--muted); }
.browse-pagination { display:flex; align-items:center; justify-content:space-between; gap:6px; margin-top:18px; }
.browse-pagination button { padding:9px 10px; font-size:.76rem; }
#browse-page { font-size:.74rem; color:var(--muted); text-align:center; }
.browse-preview { border:1px solid var(--line); border-radius:9px; padding:26px; overflow-wrap:anywhere; }
.preview-heading-row { display:flex; flex-wrap:wrap; align-items:flex-start; justify-content:space-between; gap:12px; margin-bottom:18px; }
.preview-heading-row h3 { margin:0; }
.preview-heading-row button { font-size:.8rem; }
.browse-preview .question-meta { margin-bottom:18px; }
.browse-preview .question-prompt { font-size:1.05rem; }
.browse-preview .diagram { max-width:100%; }
.browse-preview .solution { margin-top:18px; padding-top:18px; }
.selection-panel { margin-top:26px; padding-top:22px; border-top:1px solid var(--line); }
.selection-panel .section-top { align-items:center; }
.selection-panel h3 { margin:0; }
.selection-panel .section-top button { font-size:.77rem; }
#selection-status { font-size:.85rem; font-weight:600; margin-bottom:12px; }
.selection-list { list-style:none; padding:0; margin:0 0 16px; counter-reset:selection; }
.selection-item { display:flex; align-items:center; gap:12px; padding:12px 0; border-bottom:1px solid var(--line); counter-increment:selection; font-size:.84rem; }
.selection-item::before { content:counter(selection,decimal-leading-zero); flex-shrink:0; min-width:21px; color:var(--muted); font-size:.71rem; }
.selection-item>div,.selection-item>span { flex:1; min-width:0; overflow-wrap:anywhere; }
.selection-reference { display:block; color:var(--muted); font-size:.73rem; }
.selection-item button[data-remove] { flex-shrink:0; padding:8px 10px; font-size:.75rem; }
#selection-message { margin:0 0 12px; }
#selection-message:empty { display:none; }
#practise-selected { width:100%; }
.selection-note { margin:12px 0 0; }
label { display:block; font-size:.86rem; font-weight:600; }
select { display:block; width:100%; margin-top:7px; padding:11px 32px 11px 10px; border:1px solid #9299a1; background:var(--paper); color:var(--ink); border-radius:5px; min-height:46px; font-weight:400; }
.generate-row { display:flex; gap:24px; align-items:center; justify-content:space-between; padding:20px 0 24px; }
.generate-row>div { max-width:540px; }
.generate-row p { margin-bottom:6px; }
.generate-row>button { flex-shrink:0; }
#pool-status { font-size:.89rem; font-weight:600; }
.topic-disclosure { border-block:1px solid var(--line); padding:16px 0; }
summary { cursor:pointer; min-height:44px; padding:10px 0; font-weight:600; }
.topic-list { padding:0; list-style:none; margin:8px 0 0; counter-reset:topics; }
.topic-list li { border-top:1px solid var(--line); counter-increment:topics; }
.topic-list button { display:flex; gap:16px; align-items:center; width:100%; text-align:left; padding:16px 4px; border:0; border-radius:0; }
.topic-list button:before { content:counter(topics,decimal-leading-zero); font-size:.78rem; color:var(--muted); min-width:24px; }
.topic-list small { margin-left:auto; color:var(--muted); white-space:nowrap; }
.session-actions { display:flex; flex-wrap:wrap; gap:10px; align-items:center; border-block:1px solid var(--line); padding:17px 0; margin-bottom:16px; font-size:.8rem; }
.jump-label { display:flex; gap:10px; align-items:center; }
.jump-label select { width:140px; margin:0; }
#review-status { margin:0 auto 0 8px; color:var(--muted); }
.question-card { border:1px solid var(--line); border-radius:9px; padding:28px; margin:22px 0; overflow-wrap:anywhere; }
.question-meta { display:flex; flex-wrap:wrap; gap:8px; margin-bottom:22px; color:var(--muted); font-size:.76rem; }
.question-meta span { background:var(--soft); padding:3px 9px; border-radius:4px; }
.question-prompt { font-size:1.12rem; line-height:1.85; margin-bottom:24px; }
.math { display:inline-block; max-width:100%; overflow-x:auto; vertical-align:middle; padding:3px 0; }
.katex { font-size:1.1em; }
.diagram { margin:20px 0 26px; max-width:580px; }
.diagram svg { display:block; width:100%; height:auto; color:var(--ink); overflow:visible; }
.diagram figcaption { font-size:.78rem; color:var(--muted); margin:8px 0; }
.question-table { overflow-x:auto; }
.question-table table { width:100%; border-collapse:collapse; font-size:.88rem; }
.question-table caption { caption-side:top; text-align:left; font-size:.86rem; margin-bottom:12px; font-weight:600; }
.question-table th,.question-table td { border:1px solid var(--line); padding:10px 12px; text-align:left; white-space:nowrap; }
.question-table th { background:var(--soft); font-weight:600; }
.diagram text { fill:currentColor; }
.diagram text:not([font-family]) { font-family:Arial,Helvetica,sans-serif; }
.diagram text:not([font-size]) { font-size:15px; }
.answer-grid { margin:20px 0; }
.answer-grid svg { display:block; width:min(100%,420px); height:auto; background:white; }
.diagram .edge { stroke:currentColor; stroke-width:2; fill:none; }
.diagram .shape { stroke:currentColor; stroke-width:2; fill:#eef3ff; }
.diagram .curve { fill:none; stroke:#245de1; stroke-width:2.7; }
.diagram .grid { stroke:var(--line); stroke-width:1; }
.diagram .tick { font-size:13px; }
textarea { display:block; width:100%; margin:9px 0 18px; padding:12px; min-height:100px; resize:vertical; border:1px solid #9299a1; border-radius:5px; color:var(--ink); background:var(--paper); font-weight:400; }
.solution { margin:23px 0 0; border-top:1px solid var(--line); padding-top:23px; }
.final-answer { padding:16px; background:var(--soft); border-left:3px solid var(--ink); font-weight:600; }
.steps { padding-left:24px; line-height:1.9; }
.steps li { padding:4px 0; }
.graded-intro { margin:15px 0; max-width:740px; }
.graded-guidance { border-left:3px solid var(--ink); background:var(--soft); padding:16px 20px; margin:0 0 30px; }
#graded-pool-status { font-size:.89rem; font-weight:600; }
.graded-style-list { list-style:none; padding:0; margin:0; border-top:1px solid var(--line); counter-reset:graded-style; }
.graded-style-list li { display:flex; align-items:center; gap:18px; padding:20px 0; border-bottom:1px solid var(--line); counter-increment:graded-style; }
.graded-style-list li:before { content:counter(graded-style,decimal-leading-zero); color:var(--muted); font-size:.78rem; }
.graded-style-list li>div { flex:1; min-width:0; }
.graded-style-list strong { display:block; font-size:.94rem; margin-bottom:4px; }
.graded-style-list button { font-size:.82rem; flex-shrink:0; }
.graded-diagram .graded-region { fill:#eef3ff; stroke:#245de1; stroke-width:2; }
.graded-diagram { overflow-x:auto; }
.graded-diagram svg { min-width:460px; }
.graded-diagram text:not([font-size]) { font-size:18px; }
.graded-diagram .tick { font-size:15px; }
.method-checkpoints { margin:22px 0; }
.method-checkpoints h4 { font-size:.95rem; margin:0 0 10px; }
.method-checkpoints ul { list-style:none; padding:0; margin:0 0 12px; border-top:1px solid var(--line); }
.method-checkpoints li { display:flex; gap:18px; align-items:baseline; justify-content:space-between; border-bottom:1px solid var(--line); padding:9px 0; font-size:.88rem; }
.method-checkpoints li strong { white-space:nowrap; font-size:.8rem; }
.self-review { display:flex; flex-wrap:wrap; gap:10px; align-items:center; margin-top:20px; }
.self-review legend { font-size:.85rem; margin-bottom:10px; }
fieldset.self-review { border:0; padding:0; }
.self-review button[aria-pressed="true"] { background:var(--ink); color:var(--paper); border-color:var(--ink); }
.question-nav { display:flex; align-items:center; justify-content:space-between; gap:15px; }
#position { margin:0; color:var(--muted); font-size:.85rem; }
#last-note { margin-top:18px; }
.study-note { margin-top:35px; background:var(--soft); padding:22px; font-size:.89rem; border-radius:6px; }
.study-note p { margin:7px 0 0; color:var(--muted); }
footer { max-width:1180px; margin:auto; border-top:1px solid var(--line); padding:25px 32px 36px; font-size:.77rem; color:var(--muted); }
#error { color:#a22d3e; border:1px solid currentColor; padding:15px; }
.print-question { margin:25px 0; padding-bottom:15px; border-bottom:1px solid #ccc; }
.print-heading { display:flex; justify-content:space-between; gap:10px; font-size:.85rem; }
.working-space { height:90px; background:repeating-linear-gradient(white,white 29px,#ddd 30px); }
@media(max-width:980px) {
  .browse-filters { grid-template-columns:repeat(3,minmax(0,1fr)); }
  .browser-workspace { grid-template-columns:minmax(270px,.9fr) minmax(0,1.5fr); gap:22px; }
  .browse-preview { padding:21px; }
}
@media(max-width:780px) {
  .browser-workspace { grid-template-columns:1fr; gap:28px; }
  .browse-list { max-height:none; overflow-y:visible; }
  .browse-result-title { font-size:.95rem; }
  .browse-result-meta,.browse-reference { font-size:.77rem; }
  .browse-snippet { font-size:.87rem; }
  .browse-list button[data-select] { font-size:.82rem; }
}
@media(max-width:650px) {
  .site-header { padding:16px 20px; gap:12px; align-items:flex-start; }
  .site-header nav { gap:0 14px; font-size:.8rem; justify-content:flex-end; }
  main { padding:0 20px 30px; }
  .hero { padding-top:30px; gap:10px; align-items:flex-start; }
  .hero-sprite { width:75px; margin-top:37px; }
  .intro { font-size:1.1rem; }
  .hero .muted { font-size:.91rem; }
  .bank-summary { display:block; }
  .bank-summary span { display:block; margin-top:5px; font-size:.8rem; }
  .section-top { align-items:flex-start; flex-wrap:wrap; }
  .filters { grid-template-columns:1fr; gap:14px; }
  .practice-modes { gap:8px; margin-bottom:24px; padding-bottom:18px; }
  .practice-modes button { flex:1; padding-inline:10px; font-size:.85rem; }
  .browse-filters { grid-template-columns:repeat(2,minmax(0,1fr)); gap:14px; }
  .browse-search input { font-size:1rem; }
  .browse-filters select { font-size:1rem; }
  .browse-preview { padding:19px 15px; }
  .browse-preview .question-prompt { font-size:1.03rem; }
  .browse-pagination button { font-size:.82rem; padding-inline:12px; }
  .selection-item { gap:8px; }
  .selection-panel .section-top { gap:10px; }
  .generate-row { display:block; }
  .generate-row>button { width:100%; margin-top:14px; }
  .question-card { padding:19px 15px; }
  .question-prompt { font-size:1.03rem; }
  .diagram { overflow-x:auto; padding-bottom:6px; }
  .diagram svg { min-width:440px; }
  .session-actions { gap:12px 8px; }
  .session-actions>button { flex:1; font-size:.78rem; }
  #review-status { flex:1; font-size:.77rem; }
  .topic-list button { font-size:.88rem; gap:10px; }
  .topic-list small { font-size:.7rem; }
  .graded-style-list li { flex-wrap:wrap; gap:10px; }
  .graded-style-list li>div { flex-basis:calc(100% - 35px); }
  .graded-style-list button { margin-left:28px; }
  .practice-modes button { flex-basis:40%; }
  footer { padding-inline:20px; }
}
@media(max-width:420px) {
  .browse-filters { grid-template-columns:1fr; }
  .preview-heading-row { align-items:stretch; }
  .preview-heading-row>button { width:100%; }
  .selection-panel .section-top { align-items:flex-start; }
}
@media print {
  @page { margin:15mm; }
  body { background:white; color:black; font-size:11pt; }
  body.printing-practice>header,body.printing-practice>main,body.printing-practice>footer,.skip { display:none!important; }
  body.printing-practice #print-paper { display:block!important; }
  #print-paper h1 { font-size:22pt; }
  #print-paper .small { font-size:9pt; }
  .print-question { break-inside:avoid; page-break-inside:avoid; }
  .diagram { max-width:115mm; }
  .diagram svg { max-height:70mm; }
  .diagram svg { min-width:0; }
  .graded-diagram { overflow:visible; }
  .graded-diagram svg { min-width:0; }
  .question-table { overflow:visible; }
  .question-table table { font-size:9pt; }
  .question-table th,.question-table td { border-color:#777; padding:6px 8px; white-space:normal; }
  .question-prompt { font-size:11pt; line-height:1.7; }
  .math { overflow:visible; }
  .print-question h2 { font-size:13pt; }
  .working-space { height:30mm; }
  .answer-grid svg { width:120mm; height:80mm; }
  .solution { border:0; padding-top:0; }
  .final-answer { background:white; border-left:2px solid black; }
  .print-code { font-size:8pt; color:#555; }
}
.qualification-nav { display:flex; justify-content:space-between; flex-wrap:wrap; gap:12px 24px; font-size:.82rem; padding:22px 0 0; }
.qualification-nav a { min-height:44px; display:inline-flex; align-items:center; }