/* Independent lesson prototype. Replace these design tokens with the existing site's values during integration. */
:root {
  --page: #f8f7f3;
  --white: #fff;
  --ink: #203238;
  --ink-soft: #57676b;
  --accent: #234b52;
  --accent-hover: #163940;
  --beige: #f3e9d9;
  --line: #e1e5df;
  --pale: #edf3f1;
  --success: #2a725b;
  --error: #b3433a;
  --radius: 21px;
  --shadow: 0 16px 48px rgba(25, 48, 48, 0.045);
  font-synthesis: none;
}
* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 80px; }
body { margin: 0; color: var(--ink); background: var(--page); font: 16px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Inter, sans-serif; }
button, select, input { font: inherit; }
a { color: inherit; }
button { cursor: pointer; }
button:disabled { cursor: not-allowed; }
:focus-visible { outline: 3px solid #c58932; outline-offset: 3px; }
[hidden] { display: none !important; }
.container { width: min(1120px, calc(100% - 48px)); margin-inline: auto; }
.skip-link { position: fixed; top: -90px; left: 12px; z-index: 50; background: #fff; padding: 10px 16px; border-radius: 8px; }
.skip-link:focus { top: 12px; }
.site-header { border-bottom: 1px solid var(--line); background: rgba(248,247,243,.95); }
.header-inner { display: flex; justify-content: space-between; align-items: center; min-height: 88px; gap: 24px; }
.brand { display: flex; align-items: center; gap: 12px; text-decoration: none; }
.brand-mark { display: grid; place-items: center; position: relative; width: 50px; height: 50px; font: 600 28px Georgia, serif; color: #fff; background: var(--accent); border-radius: 15px; padding-right: 10px; }
.brand-equals { font: 500 15px sans-serif; position: absolute; right: 9px; color: #f1cb91; }
.brand-copy { display: flex; flex-direction: column; line-height: 1.25; }
.brand-copy strong { letter-spacing: -.035em; font-size: 16px; }
.brand-copy small { font-size: 12px; color: var(--ink-soft); margin-top: 4px; }
.site-nav { display: flex; gap: 26px; align-items: center; color: #48585d; font-size: 14px; }
.site-nav a { text-decoration: none; }
.site-nav a:hover { color: var(--accent); text-decoration: underline; text-underline-offset: 5px; }
.hero { display: grid; grid-template-columns: 1.1fr .9fr; align-items: center; gap: clamp(28px, 5vw, 74px); padding-top: 58px; padding-bottom: 48px; }
.eyebrow, .kicker, .small-overline { font-size: 11px; letter-spacing: .16em; color: #57716f; font-weight: 750; }
.eyebrow span { margin: 0 8px; color: #c1aba0; }
h1, h2, h3, p { margin-top: 0; }
h1, h2, h3 { line-height: 1.12; }
h1, h2 { font-family: Georgia, "Times New Roman", serif; font-weight: 500; }
h1 { font-size: clamp(44px, 5.2vw, 75px); letter-spacing: -.055em; margin: 20px 0 20px; }
h1 em { color: var(--accent); font-weight: 400; }
.lead { max-width: 480px; color: var(--ink-soft); font-size: 18px; line-height: 1.7; margin-bottom: 20px; }
.meta-line { display: flex; align-items: center; flex-wrap: wrap; gap: 9px; margin: 25px 0 31px; }
.meta-line span { border: 1px solid #d9ded8; border-radius: 50px; padding: 6px 12px; font-size: 12px; color: #55666a; background: #ffffff88; }
.button { display: inline-flex; justify-content: center; align-items: center; gap: 11px; min-height: 49px; padding: 12px 19px; border-radius: 10px; border: 1px solid transparent; font-weight: 700; font-size: 14px; text-decoration: none; transition: background .18s, transform .18s; }
.button:not(:disabled):active { transform: translateY(1px); }
.button-primary { background: var(--accent); color: #fff; }
.button-primary:hover { background: var(--accent-hover); }
.button-secondary { background: #fff; color: var(--accent); border-color: #c6d2ce; }
.button-secondary:hover { background: #f3f7f6; }
.hero-cta { min-width: 170px; }
.hero-art { min-height: 400px; background: var(--beige); border-radius: 32px; padding: 30px clamp(24px, 5vw, 56px) 22px; box-shadow: var(--shadow); display: flex; flex-direction: column; justify-content: center; position: relative; overflow: hidden; }
.hero-art:before { content: ""; width: 300px; height: 300px; position: absolute; right: -120px; top: -150px; border: 1px solid #d8c8b2; border-radius: 50%; }
.art-mini-label, .art-bottom { font-size: 10px; letter-spacing: .14em; color: #7d7b71; font-weight: 700; text-align: center; }
.art-mini-label { margin-bottom: 27px; }
.art-bottom { margin-top: 22px; text-transform: uppercase; }
.equation-art { display: grid; grid-template-columns: 1fr 30px 1fr; align-items: center; text-align: center; gap: 5px; color: #3a4b4a; font: 500 clamp(25px, 3vw, 37px) Georgia, serif; line-height: 1.1; white-space: nowrap; }
.equation-art .eq-sign { color: #a07c4d; }
.equation-art.final { background: #fff9ef; color: var(--accent); padding: 13px 10px; margin: 8px 9%; border: 1px solid #e7d9c4; border-radius: 12px; }
.art-rule { display: flex; justify-content: space-around; color: #a07c4d; font-size: 13px; margin: 7px 0; }
.art-rule span { border: 1px dashed #c8ae8f; border-radius: 50px; padding: 0 9px; }
.status-wrap { padding: 21px 26px; background: #fff; border-radius: 17px; border: 1px solid var(--line); box-shadow: var(--shadow); }
.status-content { display: flex; justify-content: space-between; gap: 14px; align-items: center; margin-bottom: 13px; }
.status-content strong { display: block; font-size: 14px; }
.status-description { display: block; color: var(--ink-soft); font-size: 12px; margin-top: 2px; }
.progress-percent { font-size: 14px; font-weight: 750; color: var(--accent); }
.progress-track { height: 7px; border-radius: 8px; background: #e8eeeb; overflow: hidden; }
.progress-fill { height: 100%; width: 0%; background: var(--accent); transition: width .25s; border-radius: 8px; }
.lesson-layout { display: grid; grid-template-columns: minmax(0, 1fr) 250px; align-items: start; gap: 32px; padding-top: 42px; padding-bottom: 92px; }
.lesson-body { min-width: 0; }
.lesson-section + .lesson-section { margin-top: 54px; }
.section-heading { display: flex; align-items: center; gap: 16px; margin-bottom: 20px; }
.section-number { height: 52px; width: 52px; flex: 0 0 52px; display: grid; place-items: center; border: 1px solid #cad8d0; border-radius: 16px; font: 24px Georgia, serif; color: var(--accent); }
.section-heading .kicker { margin: 0 0 4px; }
h2 { font-size: clamp(30px, 3vw, 39px); letter-spacing: -.04em; margin: 0; }
.panel { background: var(--white); border: 1px solid var(--line); border-radius: var(--radius); padding: clamp(22px, 3vw, 36px); box-shadow: var(--shadow); }
.panel + .panel { margin-top: 20px; }
.panel h3 { margin-bottom: 12px; font-size: 22px; letter-spacing: -.035em; }
.theory-panel > p { color: #4d5c5e; line-height: 1.8; }
.math-inline { font-family: Georgia, serif; font-size: 1.13em; }
.rule-box { display: flex; gap: 17px; align-items: center; background: var(--pale); border-radius: 15px; padding: 18px 20px; margin: 22px 0 31px; }
.rule-symbol { flex: 0 0 49px; display: grid; place-items: center; height: 49px; border-radius: 12px; background: #d7e4dd; color: var(--accent); font: 35px Georgia, serif; }
.rule-box strong { display: block; margin-bottom: 2px; }
.rule-box p { margin: 0; font-size: 14px; color: #526461; }
.worked-steps { padding: 0; list-style: none; counter-reset: worked; margin: 21px 0; }
.worked-steps li { counter-increment: worked; position: relative; display: grid; grid-template-columns: 46% 1fr; gap: 10px; padding: 15px 0 15px 36px; border-bottom: 1px solid var(--line); }
.worked-steps li:before { content: counter(worked) "."; position: absolute; top: 17px; left: 3px; color: #87958c; font-weight: 700; font-size: 13px; }
.step-math { font: 22px Georgia, serif; color: var(--accent); }
.step-note { align-self: center; color: var(--ink-soft); font-size: 13px; }
.check-example { color: #3c6859; background: #f0f7f0; padding: 14px 17px; border-radius: 11px; font-size: 14px; }
.panel-topline { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin-bottom: 19px; }
.pill { background: #edf2ee; color: #4e706a; letter-spacing: .11em; font-size: 10px; font-weight: 800; padding: 6px 11px; border-radius: 30px; }
.points { color: #75817e; font-size: 12px; }
.panel-subtitle { color: var(--ink-soft); font-size: 14px; line-height: 1.6; margin-bottom: 24px; }
.matching-list { display: grid; gap: 11px; }
.matching-row { display: grid; grid-template-columns: minmax(132px, .7fr) minmax(0, 1.3fr); gap: 12px; align-items: center; padding: 12px; border: 1px solid var(--line); border-radius: 12px; }
.matching-row label { display: flex; align-items: center; gap: 10px; font-size: 14px; }
.matching-letter { width: 32px; height: 32px; flex: 0 0 32px; display: grid; place-items: center; color: var(--accent); border-radius: 10px; background: #edf2ef; font-weight: 800; font-size: 12px; }
.matching-row select, .equation-card input, #student-name { width: 100%; min-width: 0; border: 1px solid #cfd7d4; color: var(--ink); background: #fff; border-radius: 9px; padding: 11px 12px; font-size: 14px; min-height: 46px; }
.matching-row select { text-overflow: ellipsis; }
.field-feedback { grid-column: 1 / -1; margin: 0; font-size: 12px; font-weight: 650; }
.field-feedback:empty { display: none; }
.is-correct { border-color: #8dc4b1 !important; background: #f8fcfa !important; }
.is-incorrect { border-color: #dfaaa3 !important; background: #fffafa !important; }
.is-correct .field-feedback { color: var(--success); }
.is-incorrect .field-feedback { color: var(--error); }
.equations-grid { display: grid; grid-template-columns: repeat(2,minmax(0,1fr)); gap: 13px; }
.equation-card { border: 1px solid var(--line); border-radius: 13px; padding: 22px; min-width: 0; display: grid; grid-template-columns: auto minmax(0,1fr); gap: 8px 10px; align-items: center; }
.question-id { color: #7b8b85; letter-spacing: .11em; font-size: 10px; font-weight: 800; grid-column: 1 / -1; }
.question-math { min-height: 63px; display: flex; align-items: center; grid-column: 1 / -1; color: var(--accent); font: clamp(21px,2.5vw,27px) Georgia, serif; white-space: nowrap; }
.equation-card label { font: 23px Georgia, serif; }
.equation-card input { min-height: 43px; padding: 8px 11px; }
.hint-button { border: 0; padding: 4px 0; background: transparent; color: #426d68; text-align: left; text-decoration: underline; text-underline-offset: 3px; font-size: 12px; justify-self: start; grid-column: 1 / -1; }
.hint-button:hover { color: var(--ink); }
.hint { grid-column: 1 / -1; background: #fff5e4; color: #675747; margin: 0; padding: 9px 11px; border-radius: 8px; font-size: 12px; }
.equation-card .field-feedback { margin-top: 0; }
.fraction { display: inline-flex; flex-direction: column; line-height: 1.18; text-align: center; vertical-align: middle; font-size: .85em; }
.fraction > span:first-child { border-bottom: 1.5px solid currentColor; padding: 0 4px 3px; }
.fraction > span:last-child { padding-top: 3px; }
.name-label { display: block; font-weight: 750; margin-bottom: 7px; font-size: 14px; }
.name-label span { color: #85918c; font-size: 12px; font-weight: 400; }
#student-name { max-width: 440px; }
.privacy-note { color: var(--ink-soft); margin: 7px 0 22px; font-size: 12px; }
.finish-actions { display: flex; flex-wrap: wrap; gap: 10px; }
.validation-message { margin: 13px 0 0; font-size: 13px; color: var(--error); font-weight: 600; }
.validation-message:empty { display: none; }
.summary { border: 1px solid #d4e4d9; background: #f1f7f2; border-radius: 15px; padding: 20px; display: flex; gap: 23px; align-items: center; margin: 22px 0 17px; }
.summary-score { flex: 0 0 98px; display: flex; align-items: baseline; gap: 5px; color: var(--accent); }
#score-big { font: 54px Georgia, serif; line-height: 1; }
.score-total { color: #82958c; font-size: 18px; }
.summary-copy h3 { margin: 0 0 7px; font-size: 18px; }
.summary-copy p { font-size: 13px; margin: 0 0 6px; }
.summary-subnote { color: var(--ink-soft); }
.button-download { width: 100%; background: #e9efea; color: var(--accent); border-color: #d1ded7; margin-top: 20px; }
.button-download:not(:disabled):hover { background: #dcebe1; }
.button-download:disabled { opacity: .49; }
.export-note { margin: 10px 0 0; color: var(--ink-soft); font-size: 12px; }
.lesson-sidebar { position: sticky; top: 30px; display: grid; gap: 20px; }
.side-card { border: 1px solid var(--line); background: #fff; border-radius: 18px; padding: 23px; }
.small-overline { display: block; margin-bottom: 16px; }
.side-segment { display: flex; gap: 11px; align-items: start; position: relative; padding-bottom: 21px; }
.side-segment:last-child { padding-bottom: 0; }
.side-segment:not(:last-child):before { content: ""; position: absolute; left: 14px; top: 32px; height: calc(100% - 34px); width: 1px; background: #dce5dd; }
.side-dot { flex: 0 0 28px; width: 28px; height: 28px; display: grid; place-items: center; background: #edf4ee; color: #497469; border-radius: 50%; font-size: 12px; font-weight: 750; }
.side-segment strong, .side-segment small { display: block; }
.side-segment strong { font-size: 13px; padding: 2px 0; }
.side-segment small { font-size: 12px; color: #84908a; margin-top: 4px; }
.side-tip { background: var(--beige); border-radius: 17px; padding: 23px; }
.side-tip p { color: #5d5b50; font: 18px/1.45 Georgia, serif; margin: 0; }
.site-footer { border-top: 1px solid var(--line); background: #f4f3ee; padding: 27px 0; }
.footer-inner { display: flex; align-items: center; justify-content: space-between; gap: 16px; font-size: 12px; color: var(--ink-soft); }
.footer-inner a { text-decoration: none; font-weight: 700; }
@media (max-width: 950px) { .lesson-layout { grid-template-columns: minmax(0,1fr); } .lesson-sidebar { position: static; display: none; } }
@media (max-width: 680px) {
  .container { width: min(100% - 28px, 1120px); }
  .header-inner { min-height: 73px; }
  .brand-mark { width: 42px; height: 42px; border-radius: 12px; font-size: 23px; }
  .brand-copy strong { font-size: 13px; }
  .brand-copy small { font-size: 11px; }
  .site-nav { gap: 13px; font-size: 12px; }
  .site-nav a:first-child { display: none; }
  .hero { grid-template-columns: 1fr; padding-top: 41px; gap: 30px; padding-bottom: 25px; }
  h1 { margin: 15px 0; }
  .lead { font-size: 16px; }
  .meta-line { margin: 18px 0 21px; }
  .hero-art { min-height: 295px; padding: 25px 27px; border-radius: 22px; }
  .equation-art { font-size: clamp(25px, 7vw, 36px); }
  .status-wrap { padding: 16px 19px; }
  .lesson-layout { padding-top: 36px; }
  .section-heading { gap: 12px; }
  .section-number { height: 44px; width: 44px; flex-basis: 44px; border-radius: 13px; font-size: 21px; }
  .panel { padding: 20px 17px; border-radius: 17px; }
  .matching-row { grid-template-columns: 1fr; gap: 9px; }
  .matching-row .field-feedback { grid-column: 1; }
  .equations-grid { grid-template-columns: 1fr; }
  .equation-card { padding: 18px; }
  .question-math { font-size: 26px; min-height: 58px; }
  .worked-steps li { grid-template-columns: 1fr; gap: 5px; }
  .summary { gap: 10px; }
  .summary-score { flex-basis: 90px; }
  #score-big { font-size: 43px; }
  .footer-inner { flex-wrap: wrap; }
}
@media (max-width: 370px) { .site-nav { gap: 8px; } .site-nav a { font-size: 11px; } .brand { gap: 7px; } .brand-copy strong { font-size: 12px; } .rule-box { align-items: start; } }
@media (prefers-reduced-motion: reduce) { *, *:before, *:after { scroll-behavior: auto !important; transition-duration: 0s !important; } }