:root {
  color-scheme: light;
  --navy: #101c35;
  --navy-soft: #192746;
  --ink: #18223b;
  --muted: #69748b;
  --paper: #f7f8fc;
  --white: #fff;
  --yellow: #ffda54;
  --cyan: #76e2d2;
  --coral: #ff8d70;
  --purple: #897bff;
  --line: #e4e8f0;
  --font: "Nunito Sans", "Segoe UI", sans-serif;
  --mono: "DM Mono", Consolas, monospace;
  font-family: var(--font);
  scroll-behavior: smooth;
}

* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); }
a { color: inherit; }
button, input, select { font: inherit; }
button, a, select { -webkit-tap-highlight-color: transparent; }

.site-header {
  position: sticky;
  z-index: 20;
  top: 0;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
  padding: 0 max(24px, calc((100vw - 1180px) / 2));
  min-height: 72px;
  background: rgb(16 28 53 / 96%);
  color: var(--white);
  backdrop-filter: blur(12px);
}
.brand { display: inline-flex; align-items: center; gap: 11px; color: inherit; font-size: 12px; font-weight: 900; letter-spacing: .09em; text-decoration: none; white-space: nowrap; }
.brand b { color: var(--yellow); }
.brand-mark { display: grid; width: 35px; height: 35px; place-items: center; border-radius: 11px; background: var(--yellow); color: var(--navy); font: 500 18px var(--mono); letter-spacing: -.1em; }
.site-header nav { display: flex; align-items: center; gap: 28px; }
.site-header nav a { color: #c8d0e0; font-size: 13px; font-weight: 800; text-decoration: none; }
.site-header nav a:hover, .site-footer a:hover { color: var(--yellow); }

.hero {
  position: relative;
  display: grid;
  min-height: 570px;
  grid-template-columns: .9fr 1.1fr;
  align-items: center;
  overflow: hidden;
  padding: 64px max(24px, calc((100vw - 1180px) / 2)) 72px;
  background:
    radial-gradient(ellipse at 82% 28%, rgb(56 87 149 / 60%), transparent 38%),
    radial-gradient(ellipse at 42% 100%, rgb(38 57 99 / 50%), transparent 43%),
    linear-gradient(128deg, #101c35, #172747 68%, #20294f);
  color: var(--white);
}
.hero-copy { position: relative; z-index: 2; max-width: 500px; }
.eyebrow { margin: 0 0 20px; color: #c2cce0; font: 500 11px var(--mono); letter-spacing: .1em; }
.pulse, .live-indicator { display: inline-block; width: 8px; height: 8px; margin-right: 8px; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 12px var(--cyan); }
h1 { margin: 18px 0 24px; font-size: clamp(58px, 8vw, 104px); font-weight: 900; line-height: .84; letter-spacing: -.075em; }
h1 span { color: var(--yellow); }
.hero-text { max-width: 415px; margin: 0 0 30px; color: #c5cede; font-size: 17px; line-height: 1.7; }
.button { display: inline-flex; align-items: center; justify-content: center; gap: 13px; min-height: 46px; padding: 0 19px; border: 0; border-radius: 12px; font-size: 13px; font-weight: 900; text-decoration: none; cursor: pointer; transition: transform .18s ease, filter .18s ease; }
.button:hover { transform: translateY(-2px); filter: brightness(1.04); }
.button:focus-visible, a:focus-visible, button:focus-visible, select:focus-visible, input:focus-visible, summary:focus-visible { outline: 3px solid var(--purple); outline-offset: 3px; }
.button-bright { background: var(--yellow); color: var(--navy); }
.hero-art { position: relative; min-height: 390px; }
.hero-road { position: absolute; right: -70px; bottom: 15px; width: 115%; overflow: visible; }
.road-shadow { fill: none; stroke: #0c1429; stroke-width: 39; stroke-linecap: round; }
.road-line { fill: none; stroke: #344365; stroke-width: 27; stroke-linecap: round; }
.hero-car { animation: cruise 5s ease-in-out infinite alternate; }
@keyframes cruise { from { transform: translate(240px, 137px); } to { transform: translate(410px, 127px); } }
.orbit { position: absolute; border: 1px solid rgb(218 230 255 / 15%); border-radius: 50%; }
.orbit-one { top: 10px; right: 40px; width: 300px; height: 300px; }
.orbit-two { top: 54px; right: 84px; width: 215px; height: 215px; }
.planet { position: absolute; border-radius: 50%; background: var(--purple); box-shadow: 0 0 24px rgb(137 123 255 / 55%); }
.planet-one { top: 48px; right: 61px; width: 13px; height: 13px; }
.planet-two { top: 247px; right: 320px; width: 8px; height: 8px; background: var(--cyan); }
.hero-equation { position: absolute; top: 46px; left: 4%; color: rgb(255 255 255 / 80%); font: 500 32px var(--mono); transform: rotate(-8deg); }
.hero-equation span { color: var(--yellow); }
.art-label { position: absolute; display: grid; gap: 3px; padding: 9px 12px; border: 1px solid rgb(255 255 255 / 13%); border-radius: 10px; background: rgb(13 23 45 / 72%); backdrop-filter: blur(10px); }
.art-label span { color: #b6c1d8; font: 400 8px var(--mono); letter-spacing: .1em; }
.art-label b { color: var(--white); font: 500 15px var(--mono); }
.label-speed { top: 128px; right: 38px; }
.label-distance { top: 213px; right: -2px; }
.label-time { bottom: 58px; left: 6%; }
.star { position: absolute; color: var(--yellow); }
.star-one { top: 116px; right: 37%; font-size: 22px; }
.star-two { top: 267px; right: 14%; color: var(--cyan); font-size: 16px; }

.quick-facts { display: grid; grid-template-columns: 1fr 1.15fr 1fr; align-items: center; gap: 28px; padding: 36px max(24px, calc((100vw - 1180px) / 2)); background: var(--yellow); }
.fact-kicker, .card-kicker, .field-label { color: #596071; font: 500 10px var(--mono); letter-spacing: .09em; }
.fact-lead h2 { margin: 9px 0 0; font-size: 26px; line-height: 1.12; letter-spacing: -.04em; }
.formula-tiles { display: flex; align-items: center; justify-content: center; gap: 13px; }
.formula-tile { display: grid; min-width: 72px; place-items: center; gap: 3px; padding: 8px 10px; border: 1px solid rgb(24 34 59 / 14%); border-radius: 11px; background: rgb(255 255 255 / 36%); }
.formula-tile strong { font: 500 25px var(--mono); }
.formula-tile span { font-size: 9px; font-weight: 800; }
.formula-equals { font: 500 24px var(--mono); }
.fraction { display: grid; gap: 3px; }
.fraction .formula-tile { min-width: 67px; padding-block: 4px; }
.fraction .formula-tile strong { font-size: 18px; }
.fraction-line { height: 2px; background: var(--ink); }
.fact-note { max-width: 235px; margin: 0; color: #373f52; font-size: 13px; line-height: 1.6; }

.section-wrap { width: min(1180px, calc(100% - 48px)); margin-inline: auto; }
.discover, .examples, .dictionary { padding-block: 85px; }
.section-heading { display: flex; align-items: end; justify-content: space-between; gap: 28px; margin-bottom: 32px; }
.eyebrow-dark { margin-bottom: 12px; color: #766b31; }
h2 { margin: 0; font-size: clamp(34px, 5vw, 52px); line-height: 1; letter-spacing: -.055em; }
.section-intro { max-width: 370px; margin: 0 0 3px; color: var(--muted); font-size: 15px; line-height: 1.65; }
.concept-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.concept-card { position: relative; min-height: 350px; padding: 24px; overflow: hidden; border: 1px solid var(--line); border-radius: 18px; background: var(--white); }
.concept-icon { display: grid; width: 46px; height: 46px; place-items: center; border-radius: 14px; background: #fff4d0; font-size: 21px; }
.concept-card:nth-child(2) .concept-icon { background: #e3f9f5; }
.concept-card:nth-child(3) .concept-icon { background: #eeeaff; }
.concept-card .card-kicker { margin: 23px 0 7px; }
.concept-card h3 { margin: 0 0 10px; font-size: 23px; letter-spacing: -.04em; }
.concept-card > p:not(.card-kicker, .demo-result) { min-height: 70px; margin: 0; color: var(--muted); font-size: 14px; line-height: 1.6; }
.mini-track { position: relative; display: grid; height: 28px; align-content: center; gap: 7px; margin: 13px 0; border-bottom: 2px dashed #d9deea; }
.mini-runner { display: block; width: 12px; height: 8px; border-radius: 8px 8px 4px 4px; background: var(--purple); }
.runner-slow { animation: mini-slow 3.5s linear infinite alternate; }
.runner-fast { background: #ff8d70; animation: mini-fast 1.8s linear infinite alternate; }
@keyframes mini-slow { to { transform: translateX(115px); } }
@keyframes mini-fast { to { transform: translateX(235px); } }
.time-bars { display: flex; height: 28px; align-items: center; gap: 6px; margin: 13px 0; }
.time-bar { height: 9px; border-radius: 9px; background: var(--cyan); }
.bar-long { width: 76%; }
.bar-short { width: 38%; background: var(--purple); }
.text-button { display: inline-flex; align-items: center; gap: 8px; padding: 0; border: 0; background: transparent; color: var(--ink); font-size: 12px; font-weight: 900; text-decoration: none; cursor: pointer; }
.text-button:hover, .example-link:hover { color: #6355d9; }
.demo-result { min-height: 18px; margin: 10px 0 0; color: #37665f; font-size: 12px; font-weight: 800; }
.unit-chips { display: flex; gap: 8px; margin: 20px 0 21px; }
.unit-chips span { display: grid; min-width: 48px; height: 36px; place-items: center; border-radius: 9px; background: #eeeaff; color: #5849bb; font: 500 13px var(--mono); }

.lab-section { padding-block: 82px 90px; background: var(--navy); color: var(--white); }
.lab-heading { margin-bottom: 38px; }
.lab-heading .section-intro { color: #bdc7da; }
.lab-grid { display: grid; grid-template-columns: minmax(285px, .78fr) minmax(0, 1.42fr); gap: 20px; align-items: stretch; }
.lab-controls, .simulation { border: 1px solid rgb(255 255 255 / 10%); border-radius: 18px; background: #192746; }
.lab-controls { padding: 24px; }
.field-label { display: block; margin-bottom: 10px; color: #b3bfd4; }
.lab-controls select, .input-fields input, .pace-control select { width: 100%; min-height: 45px; padding: 0 12px; border: 1px solid #435170; border-radius: 10px; background: #101c35; color: var(--white); }
.lab-controls select { margin-bottom: 22px; }
.input-fields { display: grid; gap: 14px; }
.input-field { display: grid; gap: 7px; }
.input-field label { color: #d4dbea; font-size: 12px; font-weight: 800; }
.input-with-unit { position: relative; }
.input-with-unit input { padding-right: 55px; }
.input-with-unit span { position: absolute; top: 50%; right: 13px; color: #c4cee0; font: 400 11px var(--mono); transform: translateY(-50%); }
.formula-display { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin: 21px 0 15px; padding: 12px 0; border-top: 1px solid rgb(255 255 255 / 10%); border-bottom: 1px solid rgb(255 255 255 / 10%); }
.formula-display .field-label { margin: 0; font-size: 9px; }
.formula-display strong { color: var(--yellow); font: 500 15px var(--mono); white-space: nowrap; }
.input-error { margin: 0 0 12px; padding: 10px; border-radius: 9px; background: #542d3b; color: #ffd9df; font-size: 12px; line-height: 1.5; }
.answer-card { display: grid; gap: 5px; padding: 16px; border-radius: 12px; background: var(--yellow); color: var(--navy); }
.answer-card > span:first-child { font: 500 9px var(--mono); letter-spacing: .08em; }
.answer-card > strong { font: 500 34px var(--mono); letter-spacing: -.06em; }
.answer-card > strong small { font-size: 15px; }
.answer-card > span:last-child { font-size: 11px; font-weight: 700; line-height: 1.5; }
.unit-hint { margin: 12px 0 0; color: #abb8cf; font-size: 10px; }
.simulation { padding: 22px 24px 19px; background: #101b33; }
.simulation-topline { display: flex; align-items: center; justify-content: space-between; gap: 12px; color: #c9d3e5; font: 500 10px var(--mono); letter-spacing: .06em; }
.simulation-badge { padding: 6px 8px; border-radius: 6px; background: rgb(255 218 84 / 13%); color: var(--yellow); font-size: 8px; }
.track-wrap { position: relative; margin-top: 16px; padding: 12px 0 0; border-radius: 12px; background: radial-gradient(ellipse at center, #1e3157, #101b33 70%); }
.track-readouts { position: relative; z-index: 1; display: flex; justify-content: space-between; gap: 6px; padding-inline: 7%; }
.track-readouts > div { display: grid; gap: 3px; }
.track-readouts span { color: #a9b6ce; font: 400 8px var(--mono); letter-spacing: .06em; }
.track-readouts strong { color: var(--white); font: 500 13px var(--mono); }
.simulation-track { display: block; width: 100%; height: auto; margin-top: -4px; overflow: visible; }
.track-back { fill: none; stroke: #293b60; stroke-width: 21; stroke-linecap: round; }
.track-center { fill: none; stroke: #8492ac; stroke-width: 2; stroke-dasharray: 2 11; stroke-linecap: round; }
.track-ticks path { stroke: #637491; stroke-width: 2; }
.track-ticks text { fill: #9cabc6; font: 500 13px var(--mono); text-anchor: middle; }
.finish-flag { filter: drop-shadow(0 0 5px rgb(255 218 84 / 35%)); }
#moving-vehicle { transition: transform .05s linear; filter: drop-shadow(0 5px 6px rgb(0 0 0 / 22%)); }
.progress-rail { height: 5px; overflow: hidden; border-radius: 6px; background: #2b3955; }
.progress-rail span { display: block; width: 0; height: 100%; border-radius: inherit; background: linear-gradient(90deg, var(--cyan), var(--yellow)); }
.scale-labels { display: flex; justify-content: space-between; padding-top: 7px; color: #aab6cb; font: 400 9px var(--mono); }
.scale-labels strong { color: var(--white); font-weight: 500; }
.sim-actions { display: flex; flex-wrap: wrap; align-items: center; gap: 9px; margin-top: 14px; }
.button-start { min-height: 40px; background: var(--cyan); color: var(--navy); }
.button-quiet { min-height: 40px; border: 1px solid #435170; background: transparent; color: var(--white); }
.pace-control { display: inline-flex; align-items: center; gap: 8px; margin-left: auto; color: #aebbd1; font-size: 10px; }
.pace-control select { width: auto; min-height: 36px; padding-inline: 8px; font-size: 10px; }
.sim-caption { margin: 12px 0 0; color: #a8b4ca; font-size: 10px; line-height: 1.55; }

.example-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 16px; }
.example-card { position: relative; min-height: 300px; padding: 25px; overflow: hidden; border: 1px solid var(--line); border-radius: 17px; background: var(--white); }
.example-number { position: absolute; top: 10px; right: 20px; color: #edf0f6; font: 500 75px var(--mono); line-height: 1; }
.example-card .card-kicker { position: relative; margin: 10px 0 9px; }
.example-card h3 { position: relative; margin: 0; font-size: 22px; letter-spacing: -.04em; }
.example-equation { display: inline-block; margin: 17px 0 6px; padding: 9px 12px; border-radius: 9px; background: #eeeaff; color: #5546b9; font: 500 17px var(--mono); }
.example-card p:not(.card-kicker) { margin: 8px 0; color: var(--muted); font-size: 13px; line-height: 1.55; }
.example-card .example-solution { color: var(--ink) !important; }
.example-link { display: inline-block; margin-top: 12px; color: #5144b6; font-size: 11px; font-weight: 900; text-decoration: none; }

.quiz-section { padding-block: 78px; background: #e9f0fc; }
.quiz-layout { display: grid; grid-template-columns: .7fr 1.3fr; gap: 45px; align-items: center; }
.quiz-intro .eyebrow { color: #766b31; }
.quiz-intro > p:not(.eyebrow) { max-width: 290px; color: var(--muted); line-height: 1.65; }
.quiz-progress { height: 7px; max-width: 250px; margin-top: 28px; overflow: hidden; border-radius: 8px; background: #d5dceb; }
.quiz-progress span { display: block; width: 20%; height: 100%; border-radius: inherit; background: var(--purple); transition: width .25s; }
.quiz-progress-label { display: inline-block; margin-top: 9px; color: #747d90; font: 500 9px var(--mono); letter-spacing: .07em; }
.quiz-card { padding: 28px; border: 1px solid #dce4f2; border-radius: 17px; background: var(--white); box-shadow: 0 15px 35px rgb(33 48 80 / 6%); }
.quiz-tag { display: inline-block; padding: 6px 9px; border-radius: 6px; background: #eeeaff; color: #5849bb; font: 500 9px var(--mono); }
.quiz-card h3 { margin: 16px 0 18px; font-size: 22px; line-height: 1.25; letter-spacing: -.035em; }
.quiz-answers { display: grid; grid-template-columns: 1fr 1fr; gap: 9px; }
.quiz-answer { min-height: 46px; padding: 10px 13px; border: 1px solid var(--line); border-radius: 10px; background: #fafbfe; color: var(--ink); text-align: left; font-size: 13px; font-weight: 800; cursor: pointer; }
.quiz-answer:hover:not(:disabled) { border-color: var(--purple); background: #f5f3ff; }
.quiz-answer.correct { border-color: #52bb99; background: #e6faf3; }
.quiz-answer.incorrect { border-color: #ed8d88; background: #fff0ef; }
.quiz-answer:disabled { cursor: default; }
.quiz-feedback { min-height: 20px; margin: 13px 0 9px; color: #3e7964; font-size: 12px; font-weight: 800; }
.quiz-feedback.is-wrong { color: #ad554e; }
.quiz-card .button-bright { min-height: 39px; font-size: 11px; }

.dictionary-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.dictionary details { padding: 0 17px; border: 1px solid var(--line); border-radius: 12px; background: var(--white); }
.dictionary summary { display: flex; min-height: 58px; align-items: center; gap: 13px; cursor: pointer; font-size: 13px; font-weight: 900; list-style: none; }
.dictionary summary::-webkit-details-marker { display: none; }
.dictionary summary::after { margin-left: auto; color: #8981cf; content: "+"; font: 500 19px var(--mono); }
.dictionary details[open] summary::after { content: "−"; }
.dictionary summary span { display: grid; width: 34px; height: 34px; place-items: center; border-radius: 9px; background: #eeeaff; color: #5849bb; font: 500 13px var(--mono); }
.dictionary details p { margin: 0; padding: 0 0 15px 47px; color: var(--muted); font-size: 12px; line-height: 1.6; }

.takeaway { position: relative; overflow: hidden; padding: 70px 24px 78px; background: var(--yellow); text-align: center; }
.takeaway-shape { position: absolute; top: -57px; right: 8%; color: rgb(24 34 59 / 7%); font: 900 260px var(--font); line-height: 1; transform: rotate(-15deg); }
.takeaway .eyebrow, .takeaway h2, .takeaway > p:not(.eyebrow), .takeaway .button { position: relative; z-index: 1; }
.takeaway .eyebrow { color: #72631e; }
.takeaway h2 { font-size: clamp(37px, 6vw, 64px); }
.takeaway h2 span { color: #755fd8; }
.takeaway > p:not(.eyebrow) { max-width: 510px; margin: 17px auto 23px; color: #4d4b43; line-height: 1.65; }
.button-dark { background: var(--navy); color: var(--white); }
.site-footer { display: flex; align-items: center; justify-content: space-between; gap: 18px; padding: 22px max(24px, calc((100vw - 1180px) / 2)); background: var(--navy); color: #c4cede; }
.brand-footer { font-size: 10px; }
.brand-footer .brand-mark { width: 29px; height: 29px; border-radius: 8px; font-size: 15px; }
.site-footer p, .site-footer > a:last-child { margin: 0; font-size: 10px; }
.site-footer > a:last-child { color: var(--white); font-weight: 800; text-decoration: none; }

@media (max-width: 850px) {
  .hero { grid-template-columns: 1fr 1fr; min-height: 520px; }
  .hero-art { transform: scale(.88); transform-origin: center right; }
  .quick-facts { grid-template-columns: 1fr 1.2fr; }
  .fact-note { grid-column: 1 / -1; max-width: none; }
  .lab-grid { grid-template-columns: 1fr; }
  .quiz-layout { grid-template-columns: 1fr 1.4fr; gap: 25px; }
}

@media (max-width: 640px) {
  .site-header { min-height: 62px; gap: 12px; padding-inline: 17px; }
  .brand { font-size: 10px; }
  .brand-mark { width: 31px; height: 31px; }
  .site-header nav { min-width: 0; flex: 1; justify-content: flex-end; gap: 13px; overflow-x: auto; scrollbar-width: none; }
  .site-header nav::-webkit-scrollbar { display: none; }
  .site-header nav a { flex: 0 0 auto; font-size: 10px; white-space: nowrap; }
  .hero { min-height: 700px; grid-template-columns: 1fr; align-content: start; padding: 54px 22px 28px; }
  h1 { font-size: clamp(64px, 18vw, 92px); }
  .hero-text { max-width: 390px; font-size: 15px; }
  .hero-art { width: 100%; min-height: 300px; margin-top: 12px; transform: none; }
  .hero-road { right: -10%; bottom: 6px; width: 114%; }
  .orbit-one { top: -5px; right: 24px; width: 240px; height: 240px; }
  .orbit-two { top: 30px; right: 59px; width: 170px; height: 170px; }
  .hero-equation { top: 6px; left: 0; font-size: 25px; }
  .label-speed { top: 85px; right: 15px; }
  .label-distance { top: 158px; right: -1px; }
  .label-time { bottom: 24px; left: 1%; }
  .planet-one { top: 25px; right: 42px; }
  .quick-facts { grid-template-columns: 1fr; gap: 18px; padding: 26px 22px; }
  .fact-lead h2 br { display: none; }
  .formula-tiles { justify-content: flex-start; }
  .fact-note { grid-column: auto; }
  .section-wrap { width: min(100% - 34px, 1180px); }
  .discover, .examples, .dictionary { padding-block: 62px; }
  .section-heading { display: block; margin-bottom: 25px; }
  .section-intro { margin-top: 15px; font-size: 13px; }
  .concept-grid, .example-grid { grid-template-columns: 1fr; }
  .concept-card { min-height: 0; }
  .concept-card > p:not(.card-kicker, .demo-result) { min-height: auto; }
  .lab-section { padding-block: 60px; }
  .lab-heading { margin-bottom: 25px; }
  .lab-controls, .simulation { padding: 18px; }
  .track-readouts { padding-inline: 3%; }
  .track-readouts strong { font-size: 11px; }
  .track-ticks text { font-size: 15px; }
  .sim-actions { gap: 7px; }
  .pace-control { width: 100%; margin: 4px 0 0; }
  .pace-control select { flex: 1; }
  .quiz-section { padding-block: 60px; }
  .quiz-layout { grid-template-columns: 1fr; gap: 25px; }
  .quiz-progress { max-width: none; }
  .quiz-card { padding: 19px; }
  .quiz-card h3 { font-size: 19px; }
  .quiz-answers { grid-template-columns: 1fr; }
  .dictionary-grid { grid-template-columns: 1fr; }
  .takeaway { padding: 55px 20px 62px; }
  .site-footer { flex-wrap: wrap; justify-content: flex-start; padding: 19px 20px; }
  .site-footer p { order: 3; flex-basis: 100%; }
  .site-footer > a:last-child { margin-left: auto; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; animation-duration: .01ms !important; animation-iteration-count: 1 !important; transition-duration: .01ms !important; }
}