/* The Flight Deck: shared visual layer. Lesson-specific diagrams keep their own styles. */
:root{color-scheme:light;--navy:#102b40;--teal:#096bdc;--lime:#a8d5ff;--ink:#102b40;--muted:#536b7d;--line:#d9e3ed;--paper:#f5f8fb;--fd-cream:#f5f8fb;--fd-sage:#edf4fb;--fd-sky:#edf4fb}
body{background:var(--fd-cream);font-size:16px;line-height:1.7}h1,h2,h3{letter-spacing:-.035em}h1{line-height:1.12}a{ text-underline-offset:4px}button,input,select{font:inherit}button{transition:background-color .15s,border-color .15s}a:focus-visible,button:focus-visible,summary:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #2a7c8c;outline-offset:4px} [hidden]{display:none!important}
.fd-skip{position:fixed;left:18px;top:-100px;background:var(--navy);color:white;padding:12px 20px;z-index:100;border-radius:8px}.fd-skip:focus{top:12px}
.site-header{max-width:1280px;padding:23px 40px;border-color:var(--line)}.brand{display:flex;align-items:center;gap:12px;text-decoration:none;color:var(--navy);font:800 24px/1.15 Manrope,'DM Sans',sans-serif;letter-spacing:-.045em;white-space:nowrap}.brand img{flex-shrink:0;display:block}.site-header nav{font-size:15px;gap:32px}.site-header nav a{padding:8px 0}.site-header nav a:hover{color:var(--teal)}
.fd-header-actions{display:flex;align-items:center;gap:22px}.fd-auth-controls{display:flex;align-items:center;min-width:34px;justify-content:flex-end}.fd-sign-in{border:1px solid var(--teal);border-radius:8px;background:transparent;color:var(--teal);padding:7px 12px;font-weight:700;cursor:pointer}.fd-sign-in:hover{background:#e8f1ef}.fd-auth-loading{font-size:12px;color:var(--muted)}
.primary{background:var(--teal);border-radius:10px;padding:14px 23px;gap:32px;font-size:16px;box-shadow:none}.primary:hover{background:#104a58}.eyebrow{font-size:11px;letter-spacing:1.7px}.intro{font-size:19px;line-height:1.7;color:var(--muted)}
.fd-hero{max-width:1280px;margin:38px auto 20px;padding:0 40px;display:grid;grid-template-columns:1.08fr 1fr;gap:6px;align-items:center}.fd-hero h1{font-size:clamp(38px,4.3vw,62px);margin:20px 0;max-width:680px}.fd-hero .intro{max-width:490px}.fd-hero .primary{margin-top:22px}.fd-hero-art{width:110%;max-width:none;height:auto;margin-left:-5%;position:relative;z-index:-1}.fd-hero-meta{font-size:13px;color:var(--muted);margin-top:12px}.fd-hero-meta span{padding:0 10px}.fd-catalog,.fd-how,.fd-curriculum{max-width:1280px;margin:28px auto 70px;padding:0 40px}.fd-section-heading{display:flex;justify-content:space-between;gap:24px;align-items:center;margin-bottom:24px}.fd-section-heading h2{font-size:29px;margin:0 0 7px}.fd-section-heading p{margin:0;color:var(--muted)}.fd-section-heading>a{font-size:14px;font-weight:600;color:var(--teal);white-space:nowrap;text-decoration:none}
.fd-course-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:16px}.fd-study-entry{max-width:620px;margin-bottom:28px}.fd-course-card{position:relative;display:flex;align-items:center;gap:16px;padding:18px 16px;background:#fff;border:1px solid var(--line);border-radius:14px;text-decoration:none;min-height:145px;transition:border-color .15s,box-shadow .15s}.fd-course-card:hover{border-color:#86a68b;box-shadow:0 6px 22px #12344308}.fd-thumbnail{display:grid;place-items:center;flex-shrink:0;width:76px;height:94px;border-radius:11px;background:var(--fd-sky)}.fd-thumbnail svg{width:68px;height:68px}.fd-tint-2,.fd-tint-5{background:var(--fd-sage)}.fd-tint-4{background:#edf0e5}.fd-tint-6{background:#f4eee2}.fd-course-copy{min-width:0}.fd-number{font-size:10px;font-weight:700;letter-spacing:1.5px;color:#657e84}.fd-course-card h3{font-size:18px;line-height:1.3;margin:6px 0;letter-spacing:-.035em}.fd-course-card p{font-size:13px;line-height:1.5;color:var(--muted);margin:0}.fd-card-arrow{font-size:18px;position:absolute;right:13px;top:12px;color:#6f878a}.fd-how{display:grid;grid-template-columns:repeat(3,1fr);gap:48px;padding-top:32px;border-top:1px solid var(--line)}.fd-how span{font-size:11px;letter-spacing:1.3px;color:var(--teal);font-weight:700}.fd-how h2{font-size:22px;margin:12px 0}.fd-how p{font-size:15px;color:var(--muted);max-width:300px}.fd-page-heading{margin:45px 0 38px}.fd-page-heading h1{font-size:48px}.fd-page-heading .intro{max-width:680px}.fd-catalog-note{margin-top:24px;color:var(--muted);font-size:14px}
.site-footer{max-width:1280px;padding:25px 40px;align-items:center;font-size:13px;gap:24px}.site-footer .brand{font-size:18px;gap:9px}.site-footer>a:last-child{color:var(--teal);text-decoration:none}.fd-about{max-width:850px;margin:65px auto 80px;padding:0 32px}.fd-about h1{font-size:50px}.fd-about h2{font-size:25px;margin-top:35px}.fd-about>p:not(.eyebrow){color:var(--muted)}.fd-about-art{float:right;width:42%;height:auto;margin:8px 0 15px 20px}
/* Lesson hierarchy: a compact stage selector and contextual sidebar. */
.fd-lesson .lesson-heading{max-width:1200px;margin:38px auto 24px;padding:0 32px}.fd-lesson .lesson-heading .eyebrow{margin-top:23px}.fd-lesson .lesson-heading h1{font-size:clamp(34px,4vw,49px);margin:12px 0}.fd-lesson .lesson-heading h1 br{display:none}.fd-lesson .lesson-heading h1 br:after{content:' '}.fd-lesson .lesson-heading .intro{max-width:780px;font-size:17px;margin-top:12px}.fd-stages{display:flex;max-width:1136px;margin:0 auto 30px;justify-content:flex-start;gap:0;font-size:16px;border-bottom:1px solid var(--line);padding:0}.fd-stages a{display:flex;align-items:center;gap:10px;position:relative;padding:16px 32px 17px 0;margin-right:38px;color:var(--muted);border-bottom:3px solid transparent;text-decoration:none}.fd-stages a span{display:grid;place-items:center;width:31px;height:31px;border-radius:50%;background:#edf0ec;color:var(--muted);font-size:13px;font-weight:700}.fd-stages a[aria-current=step]{color:var(--teal);border-color:var(--teal)}.fd-stages a[aria-current=step] span{color:white;background:var(--teal)}
.fd-lesson .lesson-layout{max-width:1200px;grid-template-columns:220px minmax(0,1fr);gap:32px;margin-bottom:35px;padding:0 32px}.fd-lesson .lesson-sidebar{display:block;position:sticky;top:24px;border:0;padding:0}.fd-big-idea{padding:22px;background:linear-gradient(135deg,#f0f3e9,#f8f8f1);border:1px solid #e2e6dc;border-radius:12px}.fd-big-idea h2{font-size:23px;line-height:1.3;margin:12px 0}.fd-big-idea p{font-size:14px;line-height:1.7;color:var(--muted)}.fd-big-idea .eyebrow{font-size:10px;color:var(--teal);margin:0;letter-spacing:1.3px}.fd-concept-icon{display:block;width:64px;height:64px;margin:20px 0 0;opacity:.85}.fd-outline{margin:18px 0;font-size:13px;padding:0 5px}.fd-outline summary{font-weight:600;cursor:pointer;color:var(--teal);padding:8px 0}.fd-outline nav{display:block;font-weight:400}.fd-lesson .lesson-sidebar .fd-outline a{font-size:13px;padding:7px 0}.fd-lesson .lesson-body{min-width:0}.fd-lesson .lesson-body h2{font-size:29px}.fd-lesson .lesson-body h3{font-size:23px}.fd-lesson .lesson-body section{margin-bottom:36px;scroll-margin-top:25px}.fd-lesson .lesson-body p,.fd-lesson .lesson-body li{color:var(--muted)}.fd-lesson .lesson-body p.key-point{color:var(--ink)}.fd-lesson .lesson-body .eyebrow{font-size:11px;color:var(--teal)}.fd-lesson .lesson-body h2:first-child{margin-top:0}.fd-lesson .text-section{padding-top:0}.fd-stage{min-width:0}.fd-stage:focus{outline:none}.fd-stage>section:last-of-type{margin-bottom:24px}.fd-stage-footer{display:flex;align-items:center;justify-content:space-between;gap:18px;padding:22px 0;border-top:1px solid var(--line);margin-top:25px}.fd-stage-footer a{text-decoration:none;font-size:14px;font-weight:600;color:var(--teal)}.fd-stage-footer .primary{color:white;margin:0;min-width:190px}.fd-stage-footer button{padding:10px 15px;background:white;color:var(--teal);border:1px solid var(--line);border-radius:8px;cursor:pointer}.fd-sources{border-top:1px solid var(--line);padding:18px 0;margin-top:12px;color:var(--muted);font-size:14px}.fd-sources>summary{cursor:pointer;color:var(--teal);font-weight:600}.fd-sources section{padding-top:24px}.fd-lesson .next-lesson{max-width:1136px;font-size:15px;margin-bottom:45px;padding:20px 0;border-color:var(--line)}
.fd-lesson .deeper{padding:17px 0;border-top:1px solid var(--line);margin-top:16px}.fd-lesson .deeper summary{cursor:pointer;color:var(--teal);font-weight:600;line-height:1.6}.fd-lesson .key-point{background:var(--fd-sage);border-left:3px solid #7c9f85;border-radius:0 8px 8px 0;padding:18px;font-weight:500}.fd-lesson .concept-checks{padding:4px 24px;background:white;border:1px solid var(--line);border-radius:12px}.fd-lesson .concept-checks .deeper:first-child{border-top:0}.fd-lesson .lesson-body :is(.st-lab,.wb-lab,.turn-lab,.stall-lab){border-color:#c7d7d4;border-radius:16px;background:#fff;box-shadow:none}.fd-lesson .lesson-body .wb-lab,.fd-lesson .lesson-body .st-lab{margin-top:20px}.fd-lesson .surface-picker button{border-radius:9px}.fd-lesson .surface-picker button[aria-pressed=true]{background:var(--teal);border-color:var(--teal)}.fd-lesson .flashcard{background:var(--navy);border-radius:14px}.fd-lesson .study-tabs{margin-top:15px}.fd-lesson .lesson-body .reference{font-size:13px}.fd-lesson .st-card,.fd-lesson .wb-card{border-color:var(--line)!important}.fd-lesson .lesson-body .wb-formula{font-size:18px!important;background:var(--fd-sage)!important;color:var(--navy)!important}
@media(max-width:1100px){.fd-course-grid{grid-template-columns:repeat(2,minmax(0,1fr))}.fd-hero h1{font-size:45px}.fd-stages{margin-left:32px;margin-right:32px}.fd-lesson .next-lesson{margin-left:32px;margin-right:32px}}
@media(max-width:900px){.fd-lesson .lesson-layout{grid-template-columns:1fr;gap:24px}.fd-lesson .lesson-sidebar{position:static;display:grid;grid-template-columns:minmax(0,1fr) auto;align-items:start;gap:20px}.fd-big-idea{padding:16px 20px}.fd-big-idea h2{font-size:19px;margin:4px 0}.fd-big-idea p{margin:5px 0}.fd-big-idea .eyebrow,.fd-concept-icon{display:none}.fd-outline{margin:3px 0;max-width:160px}.fd-outline summary{white-space:nowrap}.fd-hero{gap:0}.fd-hero h1{font-size:38px}.fd-hero .intro{font-size:17px}.fd-how{gap:25px}}
@media(max-width:650px){.site-header{padding:16px 20px;align-items:center;gap:16px}.brand{font-size:21px;gap:8px}.brand img{width:35px;height:35px}.site-header nav{flex-direction:row;gap:16px;font-size:13px;align-items:center}.fd-hero{grid-template-columns:1fr;margin:32px auto 20px;padding:0 24px}.fd-hero h1{font-size:43px;line-height:1.15}.fd-hero-art{width:90%;margin:-8px auto -12px;max-height:270px}.fd-hero .primary{width:auto}.fd-hero-meta{margin-bottom:0}.fd-catalog,.fd-how,.fd-curriculum{padding:0 20px;margin-bottom:45px}.fd-section-heading{align-items:flex-start;gap:12px}.fd-section-heading h2{font-size:26px}.fd-section-heading>a{display:none}.fd-course-grid{grid-template-columns:1fr;gap:12px}.fd-course-card{min-height:117px;padding:14px;gap:16px}.fd-thumbnail{width:72px;height:80px}.fd-course-card h3{font-size:19px}.fd-course-card p{font-size:14px}.fd-how{grid-template-columns:1fr;padding-top:22px;gap:18px}.fd-how p{max-width:none}.fd-how h2{margin:8px 0}.fd-page-heading{margin-top:30px}.fd-page-heading h1{font-size:37px}.fd-page-heading .intro{font-size:17px}.site-footer{padding:24px 20px;align-items:flex-start;gap:14px}.site-footer .brand img{width:28px;height:28px}.fd-lesson .lesson-heading{padding:0 20px;margin-top:28px}.fd-lesson .lesson-heading h1{font-size:35px}.fd-stages{margin:0 20px 22px;justify-content:space-between}.fd-stages a{font-size:14px;margin-right:0;padding:12px 4px;gap:7px}.fd-stages a span{width:27px;height:27px}.fd-lesson .lesson-layout{padding:0 16px;gap:20px}.fd-lesson .lesson-sidebar{display:block}.fd-outline{max-width:none;margin:9px 4px}.fd-outline[open] nav{display:flex;flex-direction:row;flex-wrap:wrap;gap:8px 18px}.fd-lesson .lesson-body h2{font-size:26px}.fd-lesson .lesson-body h3{font-size:22px}.fd-stage-footer{flex-wrap:wrap;gap:20px}.fd-stage-footer .primary{width:auto;min-width:0;padding:12px 15px}.fd-lesson .next-lesson{margin-left:20px;margin-right:20px}.fd-about{margin-top:35px;padding:0 24px}.fd-about h1{font-size:38px}.fd-about-art{float:none;width:100%;margin:0}.fd-lesson .lesson-body .wb-formula{font-size:16px!important}}
@media(max-width:360px){.site-header{padding:14px 14px;gap:10px}.brand{font-size:19px}.brand img{width:30px;height:30px}.site-header nav{gap:10px;font-size:12px}.fd-hero h1{font-size:37px}.fd-course-card h3{font-size:17px}.fd-thumbnail{width:60px}.fd-thumbnail svg{width:56px}.fd-lesson .lesson-heading h1{font-size:31px}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{scroll-behavior:auto!important;transition:none!important}}
@media print{.site-header,.site-footer,.fd-skip,.fd-stages,.lesson-sidebar,.fd-stage-footer,.next-lesson{display:none!important}.fd-lesson .lesson-layout{display:block;padding:0}.fd-stage[hidden]{display:block!important}.fd-stage{break-before:auto}.lesson-heading{margin:0!important}.fd-sources{display:block}body{background:white}details{break-inside:avoid}}
/* Keep step navigation horizontal even when the legacy global nav stacks. */
.fd-stages{flex-direction:row;align-items:center}
.fd-lesson-progress{max-width:1160px;margin:0 auto 18px;padding:0 40px;display:flex;align-items:center;gap:14px;color:#a34332;font-size:14px}
.fd-lesson-progress button{border:1px solid var(--teal);border-radius:8px;background:transparent;color:var(--teal);padding:7px 13px;font-weight:700;cursor:pointer}
.fd-lesson-progress button[aria-pressed=true]{background:var(--fd-sage);color:var(--navy);border-color:var(--line)}
.fd-lesson-progress button:disabled{cursor:wait;opacity:.65}
@media(max-width:650px){.fd-lesson-progress{padding:0 20px}}
.fd-skip:not(:focus){clip-path:inset(50%);width:1px;height:1px;overflow:hidden;white-space:nowrap;padding:0}
@media(max-width:360px){.site-header .brand{font-size:17px;gap:7px}.site-header .brand img{width:28px;height:28px}.site-header nav{font-size:12px;gap:9px}}
@media(max-width:650px){.fd-hero h1{font-size:clamp(32px,9vw,42px);max-width:440px}}
/* Keep the full site navigation available on narrow screens. */
@media(max-width:650px){.site-header{flex-wrap:wrap}.site-header nav{width:100%;justify-content:flex-start;gap:24px}}
/* Additional curriculum links wrap without hiding navigation on small screens. */
.site-header{flex-wrap:wrap}.site-header nav{flex-wrap:wrap;row-gap:8px}
/* Account entry and lesson save controls share the existing visual language. */
.fd-auth-controls{gap:14px;flex-wrap:wrap}.fd-profile-link{font-size:13px;font-weight:700;color:var(--teal);white-space:nowrap;text-decoration:none}
.fd-favorite-control{display:inline-flex;flex-direction:column;gap:6px}.fd-favorite-control button{border:1px solid var(--teal);border-radius:8px;padding:7px 13px;background:transparent;color:var(--teal);font:inherit;cursor:pointer}.fd-favorite-control button[aria-pressed=true]{background:var(--fd-sage)}.fd-favorite-control button:disabled{opacity:.65;cursor:wait}.fd-favorite-control [role=alert]{font-size:13px;color:#a34332}.fd-lesson-progress{flex-wrap:wrap}
@media(max-width:1100px){.fd-header-actions{flex-wrap:wrap;gap:14px;max-width:100%}}

/* Site-wide color alignment; geometry and instructional status colors stay intact. */
html body .site-header,html body .airplane-page .site-header{background:#081c2d;color:#fff;border-bottom-color:#ffffff1c}
html body .site-header .brand{color:#fff}
html body .site-header nav a{color:#d6e1eb}
html body .site-header nav a:hover,html body .site-header nav a[aria-current=page]{color:#fff;border-bottom-color:#1885ff}
html body .site-header .fd-sign-in,html body .site-header .fd-profile-link{color:#fff;border-color:#5d7388}
html body .site-header .fd-sign-in:hover{background:#203d51}
html body .site-header .fd-auth-loading{color:#b7cfdf}
html body .site-footer{background:#eaf0f4;color:#526b7d;border-color:#d9e3ed}
html body .site-footer .brand{color:#526b7d}
html body :is(a,button,summary,input,select):focus-visible{outline-color:#1488f5}
html body .primary{background:#096bdc;color:white}
html body .primary:hover{background:#0758b6}
html body .fd-course-card:hover{border-color:#80b3e9}
html body .fd-tint-2,html body .fd-tint-4,html body .fd-tint-5,html body .fd-tint-6{background:#edf4fb}
html body .fd-stages a[aria-current=step]{border-color:#096bdc;color:#096bdc}
html body .fd-decision li{border-top-color:#83b3e4}
html body .lesson-practice .flashcard.is-flipped{background:#203d51}
html body .quiz-scoreboard span:last-child,html body .quiz-result.is-ready .eyebrow{color:#a8d5ff}
html body .quiz-result.is-ready{background:radial-gradient(ellipse at top right,#234c70,transparent 70%),#102b40}
html body .lesson-practice .answer-options button:not(:disabled):hover{background:#edf4fb;border-color:#096bdc}
html body .airplane-page{--line:#d9e3ed;--paper:#f5f8fb;background:#f5f8fb}
html body .system-tabs button[aria-pressed=true],html body .mode-tabs button[aria-pressed=true],html body .switch-row input:checked+span{background:#096bdc;color:#fff}
html body .system-tabs button:hover{background:#edf4fb;color:#102b40}
html body .system-tabs button[aria-pressed=true]:hover{background:#0758b6;color:#fff}
html body .model-stage{background:radial-gradient(ellipse at 60% 40%,#203d51,#081c2d)}
html body .mode-tabs,html body .stage-button{background:#102b40;border-color:#5d7388}
html body .stage-button:hover{background:#203d51}
html body .model-sliders input{accent-color:#1885ff}
html body .model-label.selected{border-color:#82baff;color:#e0efff;background:#173d61}
html body .model-label.selected .label-index{color:#a8d5ff}

html body .fd-big-idea{background:#edf4fb;border-color:#d9e3ed}
html body .fd-stages a:not([aria-current=step]) span{background:#e6eef6}