.lesson-page { color: #e8eaf0; background: #08090b; }
.lesson-main { padding-top: 30px; padding-bottom: 90px; }
.lesson-main *, .lesson-main *::before, .lesson-main *::after { box-sizing: border-box; }
.lesson-page [hidden] { display: none !important; }
.lesson-main a { color: inherit; text-underline-offset: 5px; text-decoration-thickness: 1px; }
.lesson-main a:hover { color: #fff; }
.lesson-page :is(a, button, summary):focus-visible { outline: 2px solid #f4f5f7; outline-offset: 5px; }
.lesson-skip { position: absolute; left: 20px; top: 12px; z-index: 20; padding: 12px 18px; color: #08090b; background: #e8eaf0; transform: translateY(-160%); }
.lesson-skip:focus { transform: none; }
.lesson-breadcrumb { display: flex; flex-wrap: wrap; align-items: center; gap: 12px; color: #9fa5b0; font-size: 12px; }
.lesson-breadcrumb a { text-decoration: none; }
.lesson-hero { max-width: 880px; padding: 70px 0 66px; }
.lesson-eyebrow { margin: 0 0 22px; color: #a6adb9; font-size: 10px; font-weight: 600; line-height: 1.5; letter-spacing: .16em; text-transform: uppercase; }
.lesson-hero h1 { margin: 0 0 25px; color: #f3f4f6; font-size: clamp(56px, 8vw, 108px); font-weight: 550; line-height: .99; letter-spacing: -.065em; }
.lesson-hero h1 span { color: #aeb5c0; }
.lesson-deck { max-width: 620px; margin: 0; color: #b7bdc7; font-size: clamp(16px, 1.8vw, 20px); line-height: 1.8; }
.lesson-meta { display: flex; flex-wrap: wrap; gap: 10px 24px; margin-top: 30px; color: #c3c9d1; font-size: 10px; letter-spacing: .08em; text-transform: uppercase; }
.lesson-meta span + span::before { content: "·"; position: relative; left: -12px; color: #777f8b; }
.lesson-format-note { max-width: 620px; margin: 22px 0 0; color: #969eaa; font-size: 12px; line-height: 1.8; }
.lesson-layout { display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: clamp(32px, 6vw, 80px); padding-top: 42px; border-top: 1px solid #2a2d34; }
.lesson-sidebar { align-self: start; position: sticky; top: 30px; padding-top: 7px; }
.lesson-sidebar .lesson-eyebrow { margin-bottom: 20px; }
.lesson-sidebar ol { display: grid; gap: 17px; margin: 0; padding-left: 19px; color: #737c89; font-size: 11px; }
.lesson-sidebar li { padding-left: 5px; }
.lesson-sidebar a { color: #bac1cd; text-decoration: none; line-height: 1.6; }
.lesson-sidebar-note { margin: 30px 0 0; padding-top: 20px; border-top: 1px solid #2a2d34; color: #969eaa; font-size: 11px; line-height: 1.9; }
.lesson-content { min-width: 0; }
.lesson-section { scroll-margin-top: 32px; padding-bottom: 56px; margin-bottom: 44px; border-bottom: 1px solid #2a2d34; }
.lesson-section-label { display: flex; align-items: center; gap: 12px; margin-bottom: 20px; color: #a6adb9; font-family: monospace; font-size: 10px; letter-spacing: .09em; text-transform: uppercase; }
.lesson-section-label span { display: grid; place-items: center; width: 31px; height: 31px; border: 1px solid #343943; border-radius: 50%; }
.lesson-section-label p { margin: 0; }
.lesson-section h2 { margin: 0 0 22px; color: #f0f2f5; font-size: clamp(30px, 3.9vw, 47px); font-weight: 500; line-height: 1.15; letter-spacing: -.045em; }
.lesson-section > p, .lesson-note p, .lesson-takeaway p { color: #b3bbc6; font-size: 14px; line-height: 1.95; }
.lesson-section > p { margin: 0 0 22px; }
.lesson-section strong { color: #e9ecf1; font-weight: 600; }
.lesson-symbol { display: flex; align-items: center; gap: 28px; margin: 30px 0 28px; padding: 28px 32px; border: 1px solid #30353f; border-radius: 15px; background: #101318; }
.lesson-symbol > div { display: grid; gap: 7px; }
.lesson-symbol strong { font-size: clamp(27px, 3.7vw, 44px); letter-spacing: -.035em; font-weight: 500; }
.lesson-symbol div span { color: #a0a9b7; font-size: 11px; }
.lesson-symbol-divider { align-self: start; margin-top: 2px; color: #69717d; font-size: 40px; font-weight: 300; }
.lesson-note, .lesson-takeaway { margin-top: 28px; padding: 25px 28px; border: 1px solid #343b46; border-left: 3px solid #afb8c7; border-radius: 0 12px 12px 0; background: #101318; }
.lesson-note h3, .lesson-takeaway h3 { margin: 0 0 10px; font-size: 14px; font-weight: 600; line-height: 1.5; letter-spacing: -.01em; }
.lesson-note p, .lesson-takeaway p { margin: 0; font-size: 12px; line-height: 1.9; }
.lesson-note a { display: inline-block; margin-top: 15px; color: #d4dbe5; font-size: 11px; line-height: 1.8; }
.lesson-quote-card { margin: 28px 0; padding: clamp(22px, 3vw, 34px); border: 1px solid #414752; border-radius: 17px; background: linear-gradient(135deg, #161a20, #0e1116); }
.lesson-quote-heading { display: flex; align-items: center; justify-content: space-between; gap: 14px; padding-bottom: 26px; border-bottom: 1px solid #323842; }
.lesson-quote-heading > span:first-child { color: #e7ecf3; font-size: 17px; font-weight: 600; letter-spacing: .02em; }
.lesson-simulation-label { padding: 6px 9px; border: 1px solid #48515e; border-radius: 5px; color: #d0d7e2; font-size: 9px; letter-spacing: .06em; text-transform: uppercase; }
.lesson-quote-values { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; margin: 27px 0 24px; }
.lesson-quote-values > div { min-width: 0; }
.lesson-quote-values > div + div { padding-left: 24px; border-left: 1px solid #323842; }
.lesson-quote-values dt { margin-bottom: 10px; color: #abb4c2; font-size: 11px; letter-spacing: .1em; text-transform: uppercase; }
.lesson-quote-values dd { margin: 0 0 7px; color: #f2f5f9; font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: clamp(23px, 3.5vw, 39px); font-weight: 400; letter-spacing: -.065em; font-variant-numeric: tabular-nums; }
.lesson-quote-values dd > span { display: block; margin-top: 7px; color: #a0a9b7; font-family: ui-sans-serif, system-ui, sans-serif; font-size: 10px; line-height: 1.5; letter-spacing: 0; }
.lesson-quote-card figcaption { padding-top: 20px; border-top: 1px solid #323842; color: #a6afbd; font-size: 10px; line-height: 1.9; }
.lesson-calculation { display: flex; align-items: center; justify-content: space-between; gap: 10px; margin: 28px 0; padding: 25px 26px; border: 1px solid #343b46; border-radius: 12px; }
.lesson-calculation > div { display: grid; gap: 9px; }
.lesson-calculation div span { color: #9ea8b7; font-size: 9px; letter-spacing: .09em; text-transform: uppercase; }
.lesson-calculation strong { font-family: ui-monospace, SFMono-Regular, Consolas, monospace; font-size: clamp(17px, 2.6vw, 26px); font-weight: 400; letter-spacing: -.05em; font-variant-numeric: tabular-nums; }
.lesson-calculation > span { padding-top: 20px; color: #a1aab8; font-size: 20px; }
.lesson-calculation-result { padding: 15px 17px; border: 1px solid #596474; border-radius: 9px; background: #191f27; }
.lesson-check-toolbar { display: flex; align-items: center; justify-content: space-between; flex-wrap: wrap; gap: 10px; margin: 28px 0 4px; padding: 14px 0; border-top: 1px solid #303743; border-bottom: 1px solid #303743; }
.lesson-check-progress { margin: 0; color: #acb6c5; font-size: 11px; line-height: 1.6; }
.lesson-reset { min-height: 42px; padding: 8px 0 8px 12px; border: 0; border-radius: 3px; color: #dce3ed; background: none; font: inherit; font-size: 11px; cursor: pointer; }
.lesson-reset span { margin-left: 7px; font-size: 16px; }
.lesson-reset:hover { text-decoration: underline; text-underline-offset: 5px; }
.lesson-question { padding: 26px 0; border-bottom: 1px solid #303743; }
.lesson-question:last-of-type { border-bottom: 0; padding-bottom: 0; }
.lesson-question h3 { margin: 0 0 18px; color: #e9eef5; font-size: 16px; font-weight: 500; line-height: 1.75; letter-spacing: -.012em; }
.lesson-question h3 > span { display: block; margin-bottom: 6px; color: #8d99ab; font-family: monospace; font-size: 9px; letter-spacing: .08em; }
.lesson-static-options { display: grid; gap: 9px; padding-left: 20px; color: #b8c2d0; font-size: 13px; line-height: 1.8; }
.lesson-answer-options { display: grid; gap: 9px; }
.lesson-answer-button { display: flex; align-items: center; gap: 13px; width: 100%; min-height: 52px; padding: 13px 16px; border: 1px solid #3a4350; border-radius: 8px; text-align: left; color: #cad3df; background: #11161d; font: inherit; font-size: 12px; line-height: 1.8; cursor: pointer; transition: background 150ms ease, border-color 150ms ease; }
.lesson-choice-letter { display: grid; flex: 0 0 24px; place-items: center; height: 24px; border: 1px solid #4b5564; border-radius: 50%; color: #aeb9c9; font-family: monospace; font-size: 9px; }
.lesson-answer-button:hover { border-color: #8d9aaf; background: #1b2330; }
.lesson-answer-button[aria-pressed="true"] { border-color: #bac6d8; color: #f0f4fa; background: #26303e; }
.lesson-answer-button[aria-pressed="true"] .lesson-choice-letter { border-color: #d0d9e7; color: #10141a; background: #d0d9e7; }
.lesson-feedback { margin: 15px 0 0; padding: 15px 17px; border: 1px solid #4b586d; border-radius: 7px; color: #d0d9e6; background: #171e28; font-size: 12px; line-height: 1.9; }
.lesson-feedback[data-result="correct"] { border-color: #8594a9; background: #1c2531; }
.lesson-answer-notes { margin-top: 15px; color: #aebacc; font-size: 11px; line-height: 1.9; }
.lesson-answer-notes summary { width: fit-content; min-height: 38px; padding: 7px 2px; color: #c2cddd; cursor: pointer; }
.lesson-answer-notes p { margin: 8px 0 0; padding-left: 14px; border-left: 1px solid #4b576a; color: #aebacc; }
.lesson-no-script { color: #b3bdcc; font-size: 12px; line-height: 1.8; }
.lesson-sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.lesson-sources { margin-bottom: 0; }
.lesson-sources h2 { font-size: clamp(27px, 3vw, 37px); }
.lesson-sources > p { font-size: 12px; }
.lesson-sources ul { display: grid; gap: 19px; margin: 28px 0; padding: 0; list-style: none; }
.lesson-sources li { display: grid; gap: 7px; }
.lesson-sources li a { color: #d5deec; font-size: 12px; line-height: 1.7; }
.lesson-sources li span { color: #94a0b2; font-size: 10px; line-height: 1.7; }
.lesson-sources .lesson-source-note { margin: 0; color: #8f9aad; font-size: 10px; }
.lesson-end { display: flex; justify-content: space-between; align-items: start; flex-wrap: wrap; gap: 17px; padding: 28px 0 0; }
.lesson-end p { max-width: 300px; margin: 0; color: #aebacd; font-size: 12px; line-height: 1.8; }
.lesson-end a { padding: 4px 0; color: #e1e8f2; font-size: 11px; line-height: 1.8; }
@media (max-width: 850px) {
  .lesson-layout { grid-template-columns: 1fr; gap: 30px; }
  .lesson-sidebar { position: static; padding-top: 0; padding-bottom: 26px; border-bottom: 1px solid #2a2d34; }
  .lesson-sidebar ol { grid-template-columns: 1fr 1fr; gap: 12px 25px; }
  .lesson-sidebar-note { max-width: 560px; margin-top: 20px; padding-top: 0; border-top: 0; }
  .lesson-hero { padding-top: 55px; padding-bottom: 45px; }
}
@media (max-width: 480px) {
  .lesson-main { padding-top: 22px; padding-bottom: 60px; }
  .lesson-hero h1 { font-size: 57px; }
  .lesson-hero { padding-top: 45px; }
  .lesson-layout { padding-top: 28px; }
  .lesson-sidebar ol { grid-template-columns: 1fr; }
  .lesson-section { padding-bottom: 38px; margin-bottom: 33px; }
  .lesson-symbol { gap: 23px; padding: 24px; }
  .lesson-note, .lesson-takeaway { padding: 22px; }
  .lesson-quote-heading { align-items: start; flex-direction: column; gap: 10px; padding-bottom: 21px; }
  .lesson-quote-values { gap: 10px; }
  .lesson-quote-values > div + div { padding-left: 14px; }
  .lesson-quote-values dd { font-size: clamp(20px, 6.5vw, 28px); }
  .lesson-calculation { flex-wrap: wrap; gap: 15px; padding: 22px 18px; }
  .lesson-calculation strong { font-size: 19px; }
  .lesson-calculation-result { padding: 13px; }
}
@media (prefers-reduced-motion: reduce) {
  .lesson-answer-button { transition: none; }
}