/* the maths quizzes and books in the site's colours and fonts */
:root{--bg:#f4f9fc;--card:#ffffff;--ink:#10243a;--muted:#44576b;--line:#d3e3ee;--brand:#0a68a6;--brand-d:#0b5f96;--brand-l:#e1f2fb}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){--bg:#0b1622;--card:#122232;--ink:#e6eef5;--muted:#a6b6c4;--line:#223648;--brand:#5cc4f0;--brand-d:#7fd3f5;--brand-l:#102a3b}}
:root[data-theme="dark"]{--bg:#0b1622;--card:#122232;--ink:#e6eef5;--muted:#a6b6c4;--line:#223648;--brand:#5cc4f0;--brand-d:#7fd3f5;--brand-l:#102a3b}
body{font-family:"Source Sans 3","Segoe UI",system-ui,sans-serif;font-size:17px}
h1,h2,h3,.qtitle{font-family:"Bricolage Grotesque","Segoe UI",system-ui,sans-serif}
main h1{font-size:clamp(28px,5vw,42px);font-weight:800;line-height:1.1}
.unit-btn{align-items:center}
.unit-btn::after{content:"Start";margin-left:auto;flex:none;align-self:center;background:var(--brand);color:#fff;font-weight:700;font-size:13px;padding:7px 13px;border-radius:999px}
.form,.katex-display{max-width:100%;overflow-x:auto;overflow-y:hidden}
main p:has(.katex),main li:has(.katex),main td:has(.katex),main dd:has(.katex){overflow-x:auto;overflow-y:hidden}
/* sky title band, like the Physics book pages */
.page-hero{background:#b9e6f8;border-bottom:6px solid #1ba6dd;padding:26px 0 22px;margin-bottom:8px}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]) .page-hero{background:#10293a}}
:root[data-theme="dark"] .page-hero{background:#10293a}
.page-hero h1{margin:8px 0 0}
.page-hero .eyebrow{font-family:"JetBrains Mono",ui-monospace,monospace;font-size:13px;letter-spacing:.06em;text-transform:uppercase;color:var(--ink)}
.page-hero .lead{font-size:18px;color:var(--muted);margin:10px 0 0;max-width:40em}
.crumbs{display:flex;flex-wrap:wrap;gap:8px;margin-top:14px}
.crumbs a{font-weight:700;font-size:15px;text-decoration:none;padding:6px 12px;border-radius:10px;background:var(--card);border:1.5px solid var(--brand);color:var(--brand)}
html.dpa-contrast .page-hero{background:#000;border-color:#ffd500}
/* ---- clear exercises and answers ---- */
:root{--ans-bg:#e3f4ea;--ans-line:#1c7a46;--ans-ink:#145c37;--cm-bg:#fff0d9;--cm-line:#c25e00;--cm-ink:#8a4100}
@media (prefers-color-scheme: dark){:root:not([data-theme="light"]){--ans-bg:#0f2a1c;--ans-line:#5fd394;--ans-ink:#a5ebc3;--cm-bg:#33210a;--cm-line:#f5a54a;--cm-ink:#ffcf94}}
:root[data-theme="dark"]{--ans-bg:#0f2a1c;--ans-line:#5fd394;--ans-ink:#a5ebc3;--cm-bg:#33210a;--cm-line:#f5a54a;--cm-ink:#ffcf94}
/* bigger mathematics, more room for fractions and roots */
.katex{font-size:1.2em}
details .katex,.sol .katex,.fb .katex,.cm .katex{font-size:1.28em}
.practice p,.sol p,.ex p,.notes li,.mis li,.fb,.cm,.comp{line-height:1.9}
.qtext{font-size:1.12em;line-height:1.7}
.opt{font-size:1.05em}
/* practice questions: numbered cards */
.practice{list-style:none;padding:0;margin:0;counter-reset:pq;display:flex;flex-direction:column;gap:12px}
.practice>li{counter-increment:pq;background:var(--card);border:1px solid var(--line);border-left:5px solid var(--brand);border-radius:14px;padding:12px 14px;margin:0}
.practice>li::before{content:"Question " counter(pq);display:inline-block;background:var(--brand);color:#fff;font-weight:700;font-size:13px;padding:2px 10px;border-radius:8px;margin-bottom:6px}
.practice>li>p:first-of-type{font-size:1.06em;font-weight:600;color:var(--ink)}
/* "Show answer" button and the answer box */
.practice details{background:transparent;border:0;padding:0;margin-top:8px}
.practice summary{display:inline-flex;align-items:center;gap:6px;min-height:44px;padding:8px 16px;border-radius:10px;background:var(--brand);color:#fff;font-weight:800;list-style:none;border:2px solid var(--brand)}
.practice summary::-webkit-details-marker{display:none}
.practice details[open] summary{background:var(--card);color:var(--brand)}
.practice details>p:not(.cm){background:var(--ans-bg);border-left:5px solid var(--ans-line);border-radius:10px;padding:10px 12px;margin:10px 0 0;color:var(--ink)}
.practice details>p:not(.cm):first-of-type::before{content:"Answer";display:block;font-weight:800;color:var(--ans-ink);font-size:14px;margin-bottom:2px;font-family:"Source Sans 3",system-ui,sans-serif}
.cm{background:var(--cm-bg);border-left:5px solid var(--cm-line);border-radius:10px;padding:10px 12px;margin:8px 0 0;color:var(--ink);font-size:1rem}
.cm strong{color:var(--cm-ink)}
/* worked examples */
.ex{background:var(--card);border:1px solid var(--line);border-left:5px solid var(--brand);border-radius:14px;padding:10px 14px;margin:12px 0}
.ex .q{font-size:1.06em;font-weight:600}
.sol{border-top:1px dashed var(--line);margin-top:6px}
.sol-h{display:inline-block;background:var(--ans-bg);color:var(--ans-ink);font-weight:800;font-size:14px;padding:2px 10px;border-radius:8px;margin:.6em 0 .3em}
/* quiz feedback */
.fb{font-size:1.02em}
.fb strong{display:block;margin-bottom:4px}
@media print{.practice>li{border:1px solid #999}.practice details>p:not(.cm){background:#fff}}
html.dpa-contrast{--bg:#000;--card:#000;--ink:#fff;--muted:#fff;--line:#fff;--brand:#ffd500;--brand-d:#ffd500;--brand-l:#1a1a00}