:root {
  --ink: #14211c;
  --muted: #596861;
  --paper: #f7f5ed;
  --paper-deep: #eeecdf;
  --green: #123f35;
  --green-bright: #1e6b56;
  --lime: #d7ee93;
  --gold: #d2a91f;
  --gold-text: #806300;
  --line: #d5dbd4;
  --white: #fffefa;
  --shadow: 0 24px 70px rgba(16, 46, 38, .12);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; color: var(--ink); background: var(--paper); font-family: "Avenir Next", Avenir, "Segoe UI", Arial, sans-serif; line-height: 1.6; }
a { color: inherit; }
img, svg { display: block; max-width: 100%; }
.skip-link { position: fixed; left: 1rem; top: -5rem; z-index: 99; padding: .7rem 1rem; color: white; background: var(--green); border-radius: .5rem; }
.skip-link:focus { top: 1rem; }
.site-header { min-height: 78px; padding: max(13px, env(safe-area-inset-top)) max(28px, env(safe-area-inset-right)) 13px max(28px, env(safe-area-inset-left)); display: flex; align-items: center; justify-content: space-between; gap: 24px; border-bottom: 1px solid var(--line); background: rgba(247,245,237,.92); backdrop-filter: blur(14px); position: sticky; top: 0; z-index: 20; }
.brand { display: inline-flex; align-items: center; gap: 11px; text-decoration: none; }
.brand img { border-radius: 10px; }
.brand span { display: grid; line-height: 1.15; }
.brand strong { font-size: 1rem; letter-spacing: .02em; }
.brand small { margin-top: 4px; color: var(--muted); font-size: .69rem; letter-spacing: .07em; text-transform: uppercase; }
.site-header nav, footer nav { display: flex; align-items: center; gap: 24px; }
.site-header nav > a:not(.button) { color: var(--muted); font-size: .86rem; font-weight: 700; text-decoration: none; }
.section-shell { width: min(1180px, calc(100% - 48px)); margin-inline: auto; }
.hero { display: grid; grid-template-columns: 1.02fr .98fr; align-items: center; gap: 70px; min-height: 690px; padding-block: 68px 76px; }
.eyebrow { margin: 0 0 15px; color: var(--green-bright); font-size: .73rem; font-weight: 900; letter-spacing: .16em; text-transform: uppercase; }
h1, h2, h3, p { text-wrap: pretty; }
h1, h2 { margin: 0; font-family: Georgia, "Times New Roman", serif; letter-spacing: -.035em; line-height: 1.03; }
h1 { max-width: 720px; font-size: clamp(3.3rem, 6.1vw, 6.2rem); font-weight: 500; }
h1 span { color: var(--green-bright); }
h2 { font-size: clamp(2.2rem, 4.2vw, 4.2rem); font-weight: 500; }
h3 { line-height: 1.25; }
.hero-lede { max-width: 650px; margin: 30px 0 0; color: #42544c; font-size: 1.08rem; }
.hero-actions { display: flex; align-items: center; flex-wrap: wrap; gap: 23px; margin-top: 33px; }
.button { display: inline-flex; min-height: 48px; align-items: center; justify-content: center; padding: 12px 20px; border: 1px solid var(--green); border-radius: 999px; color: white; background: var(--green); font-size: .85rem; font-weight: 850; letter-spacing: .025em; text-decoration: none; }
.button:hover { background: var(--green-bright); }
.button-small { min-height: 39px; padding: 8px 17px; font-size: .78rem; }
.text-link { color: var(--green); font-size: .88rem; font-weight: 850; text-underline-offset: 5px; }
.trust-list { display: flex; flex-wrap: wrap; gap: 10px 24px; margin: 37px 0 0; padding: 0; color: var(--muted); font-size: .77rem; list-style: none; }
.trust-list li::before { content: "✓"; margin-right: 7px; color: var(--green-bright); font-weight: 900; }
.hero-visual { margin: 0; overflow: hidden; border: 1px solid rgba(18,63,53,.16); border-radius: 34px; background: #e9eee5; box-shadow: var(--shadow); }
.hero-visual svg { width: 100%; height: auto; }
.svg-label { fill: #163d35; font: italic 700 28px Georgia, serif; }
.plane-label { font-size: 22px; }
.hero-visual figcaption { display: grid; grid-template-columns: 38px 1fr; gap: 13px; padding: 21px 24px 23px; color: #3d5148; background: rgba(255,255,255,.68); font-size: .8rem; line-height: 1.45; }
.hero-visual figcaption strong { display: block; color: var(--ink); font-size: .88rem; }
.figure-number { color: var(--gold-text); font-size: .73rem; font-weight: 900; }
.signal-band { display: grid; grid-template-columns: 1fr 1fr; border-block: 1px solid var(--line); background: var(--white); }
.signal-band div { padding: 25px max(24px, calc((100vw - 1180px) / 2)); }
.signal-band div:first-child { padding-right: 48px; border-right: 1px solid var(--line); }
.signal-band div:last-child { padding-left: 48px; }
.signal-band strong, .signal-band span { display: block; }
.signal-band strong { font-size: .87rem; }
.signal-band span { margin-top: 4px; color: var(--muted); font-size: .75rem; }
.intro-section { display: grid; grid-template-columns: .78fr 1.22fr; gap: 80px; padding-block: 110px; border-bottom: 1px solid var(--line); }
.intro-copy { color: #43554d; font-family: Georgia, "Times New Roman", serif; font-size: 1.24rem; line-height: 1.75; }
.intro-copy p { margin: 0 0 20px; }
.tool-section { padding-block: 112px 124px; }
.section-heading { max-width: 790px; margin-bottom: 48px; }
.section-heading h2 { font-size: clamp(2.4rem, 4.4vw, 4.5rem); }
.tool-grid { display: grid; grid-template-columns: repeat(6, 1fr); gap: 16px; }
.tool-grid article { grid-column: span 2; min-height: 270px; padding: 26px; border: 1px solid var(--line); border-radius: 18px; background: var(--white); }
.tool-grid article:nth-child(4) { grid-column: 2 / span 2; }
.tool-grid article:nth-child(5) { grid-column: 4 / span 2; }
.tool-index, .mistake-grid article > span { color: var(--gold-text); font-size: .72rem; font-weight: 900; letter-spacing: .08em; }
.tool-grid h3 { margin: 41px 0 10px; font-size: 1.12rem; }
.tool-grid p { min-height: 66px; margin: 0 0 20px; color: var(--muted); font-size: .86rem; }
math { font-family: "STIX Two Math", "Cambria Math", "Times New Roman", serif; }
.tool-grid math[display="block"] { margin: 20px 0 0; overflow-x: auto; font-size: 1.02rem; }
.worked-section { padding-block: 112px; color: #f7fbf5; background: var(--green); }
.worked-shell { display: grid; grid-template-columns: .78fr 1.22fr; gap: 70px; align-items: start; }
.worked-section .eyebrow { color: var(--lime); }
.worked-intro { position: sticky; top: 114px; }
.worked-intro > p:not(.eyebrow) { max-width: 470px; margin: 29px 0 0; color: #c6d4ce; font-size: .95rem; }
.exam-habit { margin-top: 37px; padding: 19px 21px; border: 1px solid rgba(215,238,147,.42); border-radius: 14px; background: rgba(215,238,147,.07); }
.exam-habit span { color: var(--lime); font-size: .68rem; font-weight: 900; letter-spacing: .13em; }
.exam-habit p { margin: 5px 0 0; color: #eef6e8; font-size: .83rem; }
.solution-card { padding: 18px 28px 28px; border: 1px solid rgba(255,255,255,.16); border-radius: 25px; background: rgba(255,255,255,.075); }
.solution-steps { margin: 0; padding: 0; list-style: none; }
.solution-steps li { padding: 25px 3px 28px; border-bottom: 1px solid rgba(255,255,255,.14); }
.solution-steps li > div { display: flex; align-items: center; gap: 12px; }
.solution-steps li > div span { display: grid; width: 28px; height: 28px; place-items: center; border-radius: 50%; color: var(--green); background: var(--lime); font-size: .7rem; font-weight: 900; }
.solution-steps h3 { margin: 0; font-size: 1rem; }
.solution-steps p { margin: 13px 0 0; color: #d3dfda; font-size: .87rem; }
.solution-steps math[display="block"] { margin: 18px 0 0; overflow-x: auto; color: white; font-size: 1.12rem; }
.answer-strip { display: flex; align-items: baseline; gap: 18px; padding: 23px 3px 2px; color: var(--lime); }
.answer-strip > span { font-size: .68rem; font-weight: 900; letter-spacing: .12em; text-transform: uppercase; }
.answer-strip strong { color: white; font-size: .92rem; }
.mistakes-section { padding-block: 115px; }
.compact-heading { max-width: 660px; }
.mistake-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: 15px; }
.mistake-grid article { min-height: 245px; padding: 24px; border-top: 3px solid var(--green); background: var(--paper-deep); }
.mistake-grid h3 { margin: 50px 0 12px; font-size: 1rem; }
.mistake-grid p { margin: 0; color: var(--muted); font-size: .82rem; }
.workflow-section { padding-block: 105px; color: white; background: #0d2822; }
.workflow-shell { display: grid; grid-template-columns: .95fr 1.05fr; gap: 90px; align-items: center; }
.workflow-heading .eyebrow { color: var(--lime); }
.workflow-heading p:not(.eyebrow) { max-width: 510px; margin: 26px 0; color: #b9cbc4; }
.button-light { color: var(--green); background: var(--lime); border-color: var(--lime); }
.workflow-steps { margin: 0; padding: 0; border-top: 1px solid rgba(255,255,255,.16); list-style: none; }
.workflow-steps li { display: grid; grid-template-columns: 48px 1fr; gap: 18px; padding: 26px 0; border-bottom: 1px solid rgba(255,255,255,.16); }
.workflow-steps > li > span { display: grid; width: 37px; height: 37px; place-items: center; border: 1px solid rgba(215,238,147,.55); border-radius: 50%; color: var(--lime); font-size: .75rem; }
.workflow-steps h3 { margin: 0; }
.workflow-steps p { margin: 4px 0 0; color: #b9cbc4; font-size: .84rem; }
.teacher-section { padding-block: 112px 55px; }
.teacher-card { display: grid; grid-template-columns: .93fr 1.07fr; gap: 80px; padding: 58px; border-radius: 25px; background: #e4efc4; }
.teacher-card > div > p:not(.eyebrow) { margin: 24px 0 0; color: #4b5b53; }
.teacher-card ul { margin: 0; padding: 0; list-style: none; }
.teacher-card li { display: grid; grid-template-columns: 95px 1fr; gap: 16px; padding: 20px 0; border-bottom: 1px solid rgba(20,33,28,.16); }
.teacher-card li:first-child { padding-top: 5px; }
.teacher-card li strong { color: var(--green); font-size: .77rem; letter-spacing: .04em; text-transform: uppercase; }
.teacher-card li span { color: #43524b; font-size: .86rem; }
.scope-section { display: grid; grid-template-columns: .8fr 1.2fr; gap: 75px; padding-block: 70px 120px; }
.scope-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
.scope-grid article { padding: 26px; border: 1px solid var(--line); border-radius: 16px; background: var(--white); }
.scope-grid article.excluded { background: #f2ece4; }
.scope-grid h3 { margin: 0 0 12px; font-size: .95rem; }
.scope-grid p { margin: 0; color: var(--muted); font-size: .83rem; }
.faq-section { padding-block: 105px; border-top: 1px solid var(--line); }
.faq-list { border-top: 1px solid var(--line); }
.faq-list details { border-bottom: 1px solid var(--line); }
.faq-list summary { position: relative; padding: 25px 48px 25px 0; cursor: pointer; font-weight: 780; list-style: none; }
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list summary::after { content: "+"; position: absolute; right: 5px; color: var(--green-bright); font-size: 1.4rem; font-weight: 400; }
.faq-list details[open] summary::after { content: "−"; }
.faq-list details p { max-width: 820px; margin: -6px 0 25px; color: var(--muted); font-size: .88rem; }
.breadcrumb { display: flex; align-items: center; flex-wrap: wrap; gap: 8px; padding-top: 22px; color: var(--muted); font-size: .78rem; }
.breadcrumb a { color: var(--green); font-weight: 750; text-underline-offset: 4px; }
.breadcrumb span[aria-hidden="true"] { color: #8b9892; }
.related-guides { padding-block: 25px 105px; }
.related-guides .section-heading { margin-bottom: 28px; }
.related-guide-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 15px; }
.related-guide-card { display: flex; min-height: 175px; flex-direction: column; padding: 24px; border: 1px solid var(--line); border-radius: 18px; background: var(--white); text-decoration: none; transition: border-color .18s ease, transform .18s ease, box-shadow .18s ease; }
.related-guide-card:hover { border-color: var(--green-bright); transform: translateY(-2px); box-shadow: 0 14px 34px rgba(16,46,38,.08); }
.related-guide-card span { color: var(--gold-text); font-size: .68rem; font-weight: 900; letter-spacing: .11em; text-transform: uppercase; }
.related-guide-card h3 { margin: 22px 0 8px; font-family: Georgia, "Times New Roman", serif; font-size: 1.28rem; }
.related-guide-card p { margin: 0; color: var(--muted); font-size: .82rem; }
.related-guide-card strong { margin-top: auto; padding-top: 18px; color: var(--green); font-size: .78rem; }
.closing-cta { display: grid; grid-template-columns: 58px 1fr auto; gap: 22px; align-items: center; margin-bottom: 105px; padding: 37px 40px; border: 1px solid var(--line); border-radius: 20px; background: var(--white); box-shadow: 0 15px 40px rgba(16,46,38,.07); }
.closing-cta img { border-radius: 13px; }
.closing-cta .eyebrow { margin-bottom: 5px; }
.closing-cta h2 { font-size: clamp(1.5rem, 2.7vw, 2.4rem); }
footer { display: grid; grid-template-columns: 1fr auto; gap: 20px 40px; padding: 34px max(28px, calc((100vw - 1180px) / 2)); color: #c5d2cc; background: #0a1c18; font-size: .76rem; }
footer p { margin: 0; }
footer nav a { color: white; text-underline-offset: 4px; }
.draft-note { grid-column: 1 / -1; padding-top: 18px; border-top: 1px solid rgba(255,255,255,.14); color: #92a29b; font-family: ui-monospace, SFMono-Regular, Menlo, monospace; text-transform: uppercase; letter-spacing: .08em; }

@media (max-width: 900px) {
  .hero { grid-template-columns: 1fr; gap: 48px; padding-top: 58px; }
  .hero-visual { width: min(640px, 100%); }
  .intro-section, .worked-shell, .workflow-shell, .teacher-card, .scope-section { grid-template-columns: 1fr; gap: 45px; }
  .worked-intro { position: static; }
  .tool-grid { grid-template-columns: 1fr 1fr; }
  .tool-grid article, .tool-grid article:nth-child(4), .tool-grid article:nth-child(5) { grid-column: auto; }
  .tool-grid article:last-child { grid-column: 1 / -1; }
  .mistake-grid { grid-template-columns: 1fr 1fr; }
  .related-guide-grid { grid-template-columns: 1fr; }
}

@media (max-width: 620px) {
  .site-header { min-height: 68px; padding-inline: max(16px, env(safe-area-inset-left)); }
  .brand small, .site-header nav > a:not(.button) { display: none; }
  .brand img { width: 36px; height: 36px; }
  .section-shell { width: min(100% - 30px, 1180px); }
  .hero { min-height: auto; padding-block: 48px 60px; }
  h1 { font-size: clamp(2.8rem, 14.3vw, 4.2rem); }
  .hero-lede { font-size: .98rem; }
  .hero-actions { align-items: flex-start; flex-direction: column; }
  .trust-list { align-items: flex-start; flex-direction: column; }
  .hero-visual { border-radius: 22px; }
  .signal-band { grid-template-columns: 1fr; }
  .signal-band div, .signal-band div:first-child, .signal-band div:last-child { padding: 22px 18px; }
  .signal-band div:first-child { border-right: 0; border-bottom: 1px solid var(--line); }
  .intro-section, .tool-section, .mistakes-section, .faq-section { padding-block: 76px; }
  .breadcrumb { padding-top: 17px; }
  .related-guides { padding-block: 10px 76px; }
  .intro-copy { font-size: 1.08rem; }
  .tool-grid, .mistake-grid, .scope-grid { grid-template-columns: 1fr; }
  .tool-grid article:last-child { grid-column: auto; }
  .tool-grid article { min-height: auto; }
  .tool-grid p { min-height: auto; }
  .worked-section, .workflow-section { padding-block: 78px; }
  .solution-card { padding: 10px 17px 20px; }
  .solution-steps math[display="block"] { font-size: .96rem; }
  .answer-strip { align-items: flex-start; flex-direction: column; }
  .teacher-section { padding-block: 75px 40px; }
  .teacher-card { padding: 31px 23px; }
  .teacher-card li { grid-template-columns: 1fr; gap: 3px; }
  .scope-section { padding-block: 60px 88px; }
  .closing-cta { grid-template-columns: 46px 1fr; margin-bottom: 70px; padding: 26px 22px; }
  .closing-cta img { width: 46px; height: 46px; }
  .closing-cta .button { grid-column: 1 / -1; width: 100%; }
  footer { grid-template-columns: 1fr; padding-bottom: max(34px, env(safe-area-inset-bottom)); }
  footer nav { flex-wrap: wrap; }
  .draft-note { grid-column: 1; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}