:root.problem-page {
    color-scheme: light;
    scroll-behavior: smooth;
    --n-0: #fff; --n-50: #f7f8fa; --n-100: #eef0f4; --n-200: #e3e6ec;
    --n-300: #c8cdd8; --n-400: #868fa0; --n-500: #697285; --n-600: #4b5464;
    --n-700: #343b49; --n-800: #222833; --n-900: #11141b;
    --color-bg: #fff; --color-accent: #1e4bd8; --color-accent-hover: #16379e;
    --color-accent-subtle: #e8edfd; --color-on-accent: #fff;
    --font-display: var(--font-sans);
    --problem-text: #203039; --problem-muted: #566b76;
    --problem-accent: #175c88; --problem-line: #d6e1e6; --problem-gutter: 40px;
}
.problem-layout {
    width: min(1180px,calc(100% - var(--problem-gutter)*2));
    margin: 40px auto 0;
    color: var(--problem-text);
    line-height: 1.65;
}
.problem-layout a:not(.back-btn) { color: var(--problem-accent); text-underline-offset: 4px; }
.problem-toolbar { display: flex; justify-content: space-between; align-items: center; gap: 16px; max-width: 800px; margin-bottom: 32px; }
.problem-toolbar .back-btn { margin-bottom: 0; }
.problem-header { max-width: 800px; }
.problem-header h1 { font-size: 36px; font-weight: 600; line-height: 1.2; letter-spacing: -.03em; }
.problem-language { flex-shrink: 0; color: var(--problem-text); font: 14px/1.5 var(--font-sans); padding: 6px 12px; border: 1px solid var(--problem-line); border-radius: 8px; background-color: #fff; }
.problem-language-menu { position: relative; flex-shrink: 0; font: 14px/1.5 var(--font-sans); }
.problem-language-menu summary { cursor: pointer; }
.problem-language-menu summary:hover { border-color: var(--problem-accent); }
.problem-language-menu summary:focus-visible { outline: 2px solid var(--problem-accent); outline-offset: 3px; }
.problem-language-panel { position: absolute; right: 0; z-index: 30; min-width: 224px; margin-top: 8px; padding: 8px; border: 1px solid var(--problem-line); border-radius: 14px; background: #fff; box-shadow: 0 10px 15px -3px #0000001a,0 4px 6px -4px #0000001a; }
.problem-language-caption { margin: 0; padding: 4px 8px; color: var(--problem-muted); font-size: 12px; }
.problem-language-option { display: flex; align-items: center; gap: 6px; width: 100%; padding: 8px 12px; border: 0; border-radius: 4px; background: none; color: var(--problem-text); font: inherit; text-align: left; cursor: pointer; }
.problem-language-option:hover { background: #f3f7fa; }
.problem-language-option:focus-visible { outline: 2px solid var(--problem-accent); outline-offset: -2px; }
.problem-language-check { color: var(--problem-accent); }
.problem-subtitle { margin-top: 10px; color: var(--problem-muted); font-size: 13px; }
.problem-sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.problem-meta { width: 100%; max-width: 800px; border-collapse: collapse; text-align: left; margin: 24px 0 36px; border-bottom: 1px solid var(--problem-line); font-size: 13px; }
.problem-meta th { padding: 0 24px 4px 0; color: var(--problem-muted); font-size: 12px; font-weight: 400; }
.problem-meta td { padding: 0 24px 18px 0; font-family: var(--font-sans); font-variant-numeric: tabular-nums; }
.problem-reading { max-width: 800px; }
.problem-statement { font-family: var(--font-sans); font-size: 16px; line-height: 1.65; }
.problem-reading h2 { margin: 32px 0 13px; font-size: 24px; font-weight: 600; line-height: 1.3; letter-spacing: -.025em; }
.problem-statement h2:first-child { margin-top: 0; }
.problem-reading p + p { margin-top: 14px; }
.problem-reading ul,.problem-reading ol { padding-left: 23px; margin: 17px 0; }
.problem-reading li { padding-left: 1px; margin-top: 4px; }
.problem-statement a { text-decoration: underline; }
.problem-reading mjx-container[display=true] { max-width: 100%; overflow-x: auto; overflow-y: hidden; padding-block: 10px; margin: 14px 0 !important; }
.problem-statement img { max-width: 100%; height: auto; }
.problem-table-scroll { max-width: 100%; overflow-x: auto; margin-block: 18px; }
.problem-table-scroll:focus-visible { outline: 2px solid var(--problem-accent); outline-offset: 3px; }
.problem-table-scroll table { border-collapse: collapse; font: 14px/1.6 var(--font-sans); font-variant-numeric: tabular-nums; }
.problem-table-scroll th,.problem-table-scroll td { min-width: 48px; padding: 9px 14px; border: 1px solid var(--problem-line); text-align: left; vertical-align: middle; }
.problem-table-scroll th { background: #f7f9fa; font-weight: 600; }
.problem-table-scroll [align="center"] { text-align: center; }
.problem-table-scroll [align="right"] { text-align: right; }
.problem-statement pre { overflow-x: auto; padding: 16px; background: var(--n-50); }
.problem-sample-pair { display: grid; grid-template-columns: minmax(0,1fr) minmax(0,1fr); margin: 18px 0; border: 1px solid var(--problem-line); border-radius: 4px; overflow: hidden; }
.problem-sample { min-width: 0; }
.problem-sample + .problem-sample { border-left: 1px solid var(--problem-line); }
.problem-sample-heading { display: flex; justify-content: space-between; align-items: center; gap: 10px; padding: 8px 15px; min-height: 47px; background: #f7f9fa; border-bottom: 1px solid var(--problem-line); }
.problem-sample-heading h3 { font: 500 13px/1.65 var(--font-sans); color: var(--problem-muted); letter-spacing: 0; }
.problem-copy { display: inline-flex; align-items: center; gap: 5px; border: 0; border-radius: 5px; background: none; color: var(--problem-accent); font: 12px/1.65 var(--font-sans); padding: 5px 6px; cursor: pointer; }
.problem-copy:hover { background: #e9f1f6; }
.problem-copy:focus-visible { outline: 2px solid var(--problem-accent); outline-offset: 3px; }
.problem-copy svg { width: 13px; height: 13px; }
.problem-sample pre { margin: 0; padding: 15px; min-height: 58px; background: #fff; overflow: auto; font: 13px/1.75 var(--font-mono); tab-size: 4; }
.problem-sample pre code { padding: 0; background: none; color: inherit; font: inherit; }
.problem-sample-explanation { grid-column: 1 / -1; min-width: 0; padding: 24px; border-top: 1px solid var(--problem-line); font-size: 16px; }
.problem-sample-explanation img { display: block; width: 300px; max-width: 100%; height: auto; margin: auto; }
.problem-footer { margin-top: 72px; }
.problem-footer .problem-back-to-top { display: inline-block; margin-bottom: 20px; color: var(--problem-accent); text-decoration: underline; text-underline-offset: 4px; }
@media(max-width:850px) { :root.problem-page { --problem-gutter: 28px; } }
@media(max-width:650px) {
    :root.problem-page { --problem-gutter: 22px; }
    .problem-layout { margin-top: 28px; }
    .problem-toolbar { flex-wrap: wrap; gap: 12px; margin-bottom: 28px; }
    .problem-toolbar .back-btn { padding: 6px 10px; font-size: 12px; }
    .problem-header h1 { font-size: 31px; }
    .problem-meta thead { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
    .problem-meta tbody tr { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); }
    .problem-meta td { display: block; padding: 0 12px 14px 0; font-size: 13px; }
    .problem-meta td::before { content: attr(data-label); display: block; color: var(--problem-muted); font-size: 11px; margin-bottom: 3px; }
    .problem-statement { font-size: 15px; }
    .problem-reading h2 { font-size: 21px; }
    .problem-sample-pair { grid-template-columns: minmax(0,1fr); }
    .problem-sample + .problem-sample { border-left: 0; border-top: 1px solid var(--problem-line); }
    .problem-sample-heading { padding-inline: 13px; }
    .problem-sample-explanation { padding: 18px; font-size: 15px; }
    .problem-footer { margin-top: 42px; }
}
@media(prefers-reduced-motion:reduce) { :root.problem-page { scroll-behavior: auto; } }