@font-face{font-family:DM Sans Variable;font-style:normal;font-display:swap;font-weight:100 1000;src:url(/assets/dm-sans-latin-ext-wght-normal-BOFOeGcA.woff2)format("woff2-variations");unicode-range:U+100-2BA,U+2BD-2C5,U+2C7-2CC,U+2CE-2D7,U+2DD-2FF,U+304,U+308,U+329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF}@font-face{font-family:DM Sans Variable;font-style:normal;font-display:swap;font-weight:100 1000;src:url(/assets/dm-sans-latin-wght-normal-Xz1IZZA0.woff2)format("woff2-variations");unicode-range:U+??,U+131,U+152-153,U+2BB-2BC,U+2C6,U+2DA,U+2DC,U+304,U+308,U+329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}@font-face{font-family:Newsreader Variable;font-style:normal;font-display:swap;font-weight:200 800;src:url(/assets/newsreader-vietnamese-wght-normal-Czsa-EzN.woff2)format("woff2-variations");unicode-range:U+102-103,U+110-111,U+128-129,U+168-169,U+1A0-1A1,U+1AF-1B0,U+300-301,U+303-304,U+308-309,U+323,U+329,U+1EA0-1EF9,U+20AB}@font-face{font-family:Newsreader Variable;font-style:normal;font-display:swap;font-weight:200 800;src:url(/assets/newsreader-latin-ext-wght-normal-C-3rgBeH.woff2)format("woff2-variations");unicode-range:U+100-2BA,U+2BD-2C5,U+2C7-2CC,U+2CE-2D7,U+2DD-2FF,U+304,U+308,U+329,U+1D00-1DBF,U+1E00-1E9F,U+1EF2-1EFF,U+2020,U+20A0-20AB,U+20AD-20C0,U+2113,U+2C60-2C7F,U+A720-A7FF}@font-face{font-family:Newsreader Variable;font-style:normal;font-display:swap;font-weight:200 800;src:url(/assets/newsreader-latin-wght-normal-CCVVNp6i.woff2)format("woff2-variations");unicode-range:U+??,U+131,U+152-153,U+2BB-2BC,U+2C6,U+2DA,U+2DC,U+304,U+308,U+329,U+2000-206F,U+20AC,U+2122,U+2191,U+2193,U+2212,U+2215,U+FEFF,U+FFFD}*,:before,:after,::backdrop{--tw-border-spacing-x:0;--tw-border-spacing-y:0;--tw-translate-x:0;--tw-translate-y:0;--tw-rotate:0;--tw-skew-x:0;--tw-skew-y:0;--tw-scale-x:1;--tw-scale-y:1;--tw-pan-x: ;--tw-pan-y: ;--tw-pinch-zoom: ;--tw-scroll-snap-strictness:proximity;--tw-gradient-from-position: ;--tw-gradient-via-position: ;--tw-gradient-to-position: ;--tw-ordinal: ;--tw-slashed-zero: ;--tw-numeric-figure: ;--tw-numeric-spacing: ;--tw-numeric-fraction: ;--tw-ring-inset: ;--tw-ring-offset-width:0px;--tw-ring-offset-color:#fff;--tw-ring-color:#3b82f680;--tw-ring-offset-shadow:0 0 #0000;--tw-ring-shadow:0 0 #0000;--tw-shadow:0 0 #0000;--tw-shadow-colored:0 0 #0000;--tw-blur: ;--tw-brightness: ;--tw-contrast: ;--tw-grayscale: ;--tw-hue-rotate: ;--tw-invert: ;--tw-saturate: ;--tw-sepia: ;--tw-drop-shadow: ;--tw-backdrop-blur: ;--tw-backdrop-brightness: ;--tw-backdrop-contrast: ;--tw-backdrop-grayscale: ;--tw-backdrop-hue-rotate: ;--tw-backdrop-invert: ;--tw-backdrop-opacity: ;--tw-backdrop-saturate: ;--tw-backdrop-sepia: ;--tw-contain-size: ;--tw-contain-layout: ;--tw-contain-paint: ;--tw-contain-style: }*,:before,:after{box-sizing:border-box;border:0 solid #e5e7eb}:before,:after{--tw-content:""}html,:host{-webkit-text-size-adjust:100%;tab-size:4;font-feature-settings:normal;font-variation-settings:normal;-webkit-tap-highlight-color:transparent;font-family:DM Sans Variable,DM Sans,ui-sans-serif,system-ui,sans-serif;line-height:1.5}body{line-height:inherit;margin:0}hr{height:0;color:inherit;border-top-width:1px}abbr:where([title]){-webkit-text-decoration:underline dotted;text-decoration:underline dotted}h1,h2,h3,h4,h5,h6{font-size:inherit;font-weight:inherit}a{color:inherit;-webkit-text-decoration:inherit;text-decoration:inherit}b,strong{font-weight:bolder}code,kbd,samp,pre{font-feature-settings:normal;font-variation-settings:normal;font-family:JetBrains Mono,ui-monospace,SFMono-Regular,monospace;font-size:1em}small{font-size:80%}sub,sup{vertical-align:baseline;font-size:75%;line-height:0;position:relative}sub{bottom:-.25em}sup{top:-.5em}table{text-indent:0;border-color:inherit;border-collapse:collapse}button,input,optgroup,select,textarea{font-feature-settings:inherit;font-variation-settings:inherit;font-family:inherit;font-size:100%;font-weight:inherit;line-height:inherit;letter-spacing:inherit;color:inherit;margin:0;padding:0}button,select{text-transform:none}button,input:where([type=button]),input:where([type=reset]),input:where([type=submit]){-webkit-appearance:button;background-color:#0000;background-image:none}:-moz-focusring{outline:auto}:-moz-ui-invalid{box-shadow:none}progress{vertical-align:baseline}::-webkit-inner-spin-button{height:auto}::-webkit-outer-spin-button{height:auto}[type=search]{-webkit-appearance:textfield;outline-offset:-2px}::-webkit-search-decoration{-webkit-appearance:none}::-webkit-file-upload-button{-webkit-appearance:button;font:inherit}summary{display:list-item}blockquote,dl,dd,h1,h2,h3,h4,h5,h6,hr,figure,p,pre{margin:0}fieldset{margin:0;padding:0}legend{padding:0}ol,ul,menu{margin:0;padding:0;list-style:none}dialog{padding:0}textarea{resize:vertical}input::-moz-placeholder{opacity:1;color:#9ca3af}textarea::-moz-placeholder{opacity:1;color:#9ca3af}input::placeholder,textarea::placeholder{opacity:1;color:#9ca3af}button,[role=button]{cursor:pointer}:disabled{cursor:default}img,svg,video,canvas,audio,iframe,embed,object{vertical-align:middle;display:block}img,video{max-width:100%;height:auto}[hidden]:where(:not([hidden=until-found])){display:none}.container{width:100%}@media (width>=640px){.container{max-width:640px}}@media (width>=768px){.container{max-width:768px}}@media (width>=1024px){.container{max-width:1024px}}@media (width>=1280px){.container{max-width:1280px}}@media (width>=1536px){.container{max-width:1536px}}.sr-only{clip:rect(0, 0, 0, 0);white-space:nowrap;border-width:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}.visible{visibility:visible}.fixed{position:fixed}.relative{position:relative}.mx-auto{margin-left:auto;margin-right:auto}.mb-3{margin-bottom:.75rem}.mb-6{margin-bottom:1.5rem}.block{display:block}.table{display:table}.hidden{display:none}.max-w-2xl{max-width:42rem}.grow{flex-grow:1}.py-20{padding-top:5rem;padding-bottom:5rem}.text-center{text-align:center}.text-\[11px\]{font-size:11px}.text-\[2\.6rem\]{font-size:2.6rem}.font-bold{font-weight:700}.text-ink-300{--tw-text-opacity:1;color:rgb(123 120 116/var(--tw-text-opacity,1))}.text-ink-400{--tw-text-opacity:1;color:rgb(63 61 58/var(--tw-text-opacity,1))}.outline{outline-style:solid}.filter{filter:var(--tw-blur) var(--tw-brightness) var(--tw-contrast) var(--tw-grayscale) var(--tw-hue-rotate) var(--tw-invert) var(--tw-saturate) var(--tw-sepia) var(--tw-drop-shadow)}:root{--paper:#f9f8f4;--surface:#fffefa;--ink:#272b25;--muted:#66695f;--line:#d8d9d0;--red:#a83b2d;--green:#293e32;--yellow:#e9eabe;--serif:"Newsreader Variable", Georgia, serif;--sans:"DM Sans Variable", sans-serif}*{box-sizing:border-box}html{scroll-behavior:smooth;text-rendering:optimizelegibility;-webkit-font-smoothing:antialiased;scroll-padding-top:30px}body{background:var(--paper);color:var(--ink);font-family:var(--sans);margin:0;font-size:15px;line-height:1.6}button,input,textarea,select{font:inherit}button,a{-webkit-tap-highlight-color:transparent}button{cursor:pointer}button:disabled{cursor:wait;opacity:.5}a{color:inherit;text-decoration:none}h1,h2,h3,p,figure,blockquote{margin:0}h1,h2,h3{font-weight:500}h1,h2{font-family:var(--serif);letter-spacing:-.035em;line-height:1.04}p{overflow-wrap:break-word}svg{flex-shrink:0}::selection{background:var(--yellow)}:focus-visible{outline:2px solid var(--red);outline-offset:5px}.main-content:focus{outline:none}.site-shell{flex-direction:column;min-height:100vh;display:flex}.main-content{flex:1;min-width:0}.skip-link{background:var(--green);color:#fff;z-index:100;padding:12px 20px;position:fixed;top:-100px;left:20px}.skip-link:focus{top:10px}.site-header{border-bottom:1px solid var(--line)}.header-inner{align-items:center;gap:45px;max-width:1400px;height:94px;margin:auto;padding:0 52px;display:flex}.wordmark{font-family:var(--serif);letter-spacing:-.07em;white-space:nowrap;font-size:37px;font-weight:600;line-height:1}.wordmark-period{color:var(--red)}.site-header nav{gap:32px;margin:auto;font-size:14px;display:flex}.site-header nav a{border-bottom:2px solid #0000;padding:34px 0 30px}.site-header nav a.active{border-color:var(--red);color:var(--red)}.site-header nav a:hover{color:var(--red)}.header-map{align-items:center;gap:18px;font-size:13px;display:flex}.home-page,.page-wrap{max-width:1400px;margin:auto;padding:0 52px}.hero{grid-template-columns:.85fr 1.15fr;align-items:center;gap:60px;padding:64px 0 58px;display:grid}.eyebrow{font:500 11px/1.5 var(--sans);letter-spacing:.13em;text-transform:uppercase;color:var(--muted)}.hero h1{letter-spacing:-.045em;margin:24px 0 25px;font-size:clamp(54px,5.85vw,86px);line-height:.96}.hero-description{color:#54574e;max-width:360px;margin-bottom:27px;font-size:16px;line-height:1.7}.hero-footnote{color:var(--muted);letter-spacing:.02em;margin-top:17px;font-size:10px}.hero-figure{min-width:0;margin-top:5px}.hero-figure img{-o-object-fit:cover;object-fit:cover;width:100%;height:475px;display:block}.hero-figure figcaption{color:var(--muted);justify-content:space-between;gap:15px;margin-top:14px;font-size:10px;display:flex}.button{border:1px solid #0000;border-radius:2px;justify-content:center;align-items:center;gap:16px;min-height:45px;padding:11px 20px;font-size:13px;font-weight:500;line-height:1.5;transition:background .16s,color .16s,border-color .16s;display:inline-flex}.button-red{background:var(--red);color:#fff}.button-red:hover{background:#873125}.button-dark{background:var(--green);color:#fff}.button-dark:hover{background:#15291e}.button-outline{border-color:var(--line);background:0 0}.button-outline:hover{background:#efefe6;border-color:#8d9489}.button-outline[aria-pressed=true]{background:var(--green);border-color:var(--green);color:#fff}.text-link{align-items:center;gap:12px;font-size:13px;font-weight:500;display:inline-flex}.text-link:hover{color:var(--red)}.small-link{color:var(--muted);align-items:center;gap:6px;font-size:12px;display:inline-flex}.small-link:hover{text-decoration:underline}.section-heading{justify-content:space-between;align-items:end;gap:24px;margin-bottom:32px;display:flex}.section-heading h2{margin-top:9px;font-size:43px}.section-heading>p{color:var(--muted);font-size:13px;line-height:1.7}.strand-section{border-top:1px solid var(--ink);padding:43px 0 49px}.strand-grid{-moz-column-gap:55px;grid-template-columns:1fr 1fr;column-gap:55px;display:grid}.strand-link{border-top:1px solid var(--line);grid-template-columns:40px 1fr 24px;align-items:center;gap:15px;padding:26px 0;transition:background .15s;display:grid}.strand-link:nth-last-child(-n+2){border-bottom:1px solid var(--line)}.strand-number{font-family:var(--serif);align-self:start;margin-top:8px;font-size:28px;line-height:1.1}.strand-question{color:var(--muted);margin-bottom:3px;font-size:11px}.strand-link h3{font-family:var(--serif);letter-spacing:-.025em;font-size:28px;line-height:1.2}.strand-link p:last-child{color:var(--muted);margin-top:5px;font-size:12px}.strand-link:hover h3{color:var(--red)}.strand-link>svg{transition:transform .18s}.strand-link:hover>svg{transform:translate(2px,-2px)}.map-link{margin-top:25px}.starting-section{padding:34px 0 65px}.guide-row{border-top:1px solid var(--line);grid-template-columns:36px minmax(0,1fr) 140px 40px 30px;align-items:center;gap:18px;padding:24px 0;display:grid}.guide-row:last-child{border-bottom:1px solid var(--line)}.row-number{font:12px var(--sans);color:var(--muted);font-variant-numeric:tabular-nums}.guide-row-main{min-width:0}.meta{text-transform:uppercase;letter-spacing:.06em;color:var(--muted);gap:15px;margin-bottom:5px;font-size:10px;display:flex}.guide-row h3{font-family:var(--serif);letter-spacing:-.015em;font-size:27px;line-height:1.3}.guide-row-main:hover h3{color:var(--red)}.guide-row p{color:var(--muted);margin-top:3px;font-size:13px}.row-time{font-size:13px}.row-time>span{color:var(--muted);font-size:11px;display:block}.row-mobile-meta{display:none}.icon-button,.row-arrow{background:0 0;border:0;border-radius:2px;justify-content:center;align-items:center;width:44px;height:44px;display:inline-flex}.icon-button:hover,.row-arrow:hover{background:#eceee5}.save-control{display:inline-flex;position:relative}.save-control .error-text{z-index:2;background:#fff;width:180px;padding:8px;position:absolute;top:100%;right:0}.principle-band{background:var(--yellow);grid-template-columns:.5fr 1fr 1fr;align-items:start;gap:36px;margin:0 -52px;padding:48px 52px 50px;display:grid}.principle-band h2{font-size:46px;line-height:1.04}.principle-band>div>p{margin-bottom:23px;font-size:14px;line-height:1.75}.site-footer{width:100%;max-width:1400px;margin:auto;padding:54px 52px 30px}.footer-top{border-bottom:1px solid var(--line);justify-content:space-between;align-items:center;gap:20px;padding-bottom:28px;display:flex}.footer-top .wordmark{font-size:32px}.footer-top>p{font-family:var(--serif);font-size:24px}.footer-top>a:last-child{align-items:center;gap:9px;font-size:12px;display:flex}.footer-bottom{color:var(--muted);justify-content:space-between;gap:20px;padding-top:17px;font-size:10px;display:flex}.page-heading{max-width:840px;padding:55px 0 38px}.page-heading h1{margin:17px 0;font-size:clamp(43px,5vw,68px)}.page-heading>p:last-child{color:var(--muted);max-width:650px;font-size:16px;line-height:1.7}.library-toolbar{border-bottom:1px solid var(--ink);justify-content:space-between;align-items:center;gap:20px;padding-bottom:20px;display:flex}.view-switch{gap:3px;display:flex}.view-switch button{background:0 0;border:1px solid #0000;border-radius:2px;align-items:center;gap:9px;padding:10px 14px;font-size:13px;display:flex}.view-switch button[aria-pressed=true]{background:var(--green);color:#fff}.view-switch button:hover{border-color:var(--line)}.library-layout{grid-template-columns:230px minmax(0,1fr);gap:48px;margin-top:30px;display:grid}.library-sidebar .eyebrow{margin-bottom:17px}.library-sidebar>button{text-align:left;border:0;border-bottom:1px solid var(--line);width:100%;color:var(--muted);background:0 0;justify-content:space-between;align-items:center;gap:8px;padding:13px 10px;font-size:11px;display:flex}.sidebar-name{color:var(--ink);margin-left:10px;font-size:12px}.library-sidebar>button.selected{background:var(--yellow);color:var(--ink)}.library-sidebar>button:hover{background:#efefe5}.sidebar-note{color:var(--muted);margin:32px 10px;font-size:12px;line-height:1.7}.sidebar-note>p{color:var(--ink);margin-bottom:8px;font-weight:600}.search-field{background:var(--surface);border:1px solid var(--line);align-items:center;gap:12px;min-height:51px;padding:0 16px;display:flex}.search-field input{background:0 0;border:0;outline:none;width:100%;min-width:0;padding:14px 0;font-size:13px}.search-field:focus-within{outline:2px solid var(--red);outline-offset:2px}.search-field>button{background:0 0;border:0;font-size:12px}.filter-row{justify-content:space-between;align-items:center;gap:15px;margin:19px 0;display:flex}.filter-row>label:first-child{color:var(--muted);align-items:center;gap:12px;font-size:11px;display:flex}select{background:var(--surface);border:1px solid var(--line);color:var(--ink);border-radius:2px;padding:9px 30px 9px 10px;font-size:12px}.quick-filter{cursor:pointer;align-items:center;gap:8px;font-size:12px;display:flex}.quick-filter input{width:17px;height:17px;accent-color:var(--green)}.result-count{color:var(--muted);padding:15px 0;font-size:11px}.strand-intro{padding:24px 0 14px}.strand-intro h2{margin-bottom:12px;font-size:35px}.strand-intro p{color:var(--muted);font-size:14px;line-height:1.8}.library-results .guide-row{grid-template-columns:25px minmax(0,1fr) 80px 40px;gap:15px}.library-results .row-arrow,.library-results .row-time>span{display:none}.empty-state{text-align:center;border-bottom:1px solid var(--line);padding:60px 20px}.empty-state h2{font-size:36px}.empty-state p{color:var(--muted);max-width:440px;margin:18px auto}.map-explainer{background:var(--yellow);padding:22px 25px;font-size:13px}.map-explainer>p{margin-top:7px;line-height:1.7}.learning-strand{border-bottom:1px solid var(--line);padding:40px 0}.learning-strand>header{align-items:center;gap:24px;display:flex}.learning-strand>header>span{font:38px var(--serif)}.learning-strand h2{margin-top:5px;font-size:35px}.strand-basis{color:var(--muted);margin:20px 0 26px;font-size:13px;line-height:1.8}.trajectory-grid{grid-template-columns:repeat(3,1fr);gap:20px;display:grid}.stage-label{border-top:2px solid var(--green);text-transform:uppercase;letter-spacing:.1em;justify-content:space-between;align-items:center;padding-top:10px;font-size:10px;display:flex}.trajectory-grid>div:last-child .stage-label>svg{display:none}.trajectory-grid h3{font:22px/1.15 var(--serif);min-height:50px;margin:18px 0}.trajectory-grid ul{margin:0;padding:0;list-style:none}.trajectory-grid a{justify-content:space-between;align-items:start;gap:8px;padding:9px 0;font-size:12px;display:flex}.trajectory-grid a:hover{color:var(--red)}.source-disclosure{border-top:1px solid var(--line);border-bottom:1px solid var(--line);margin-top:24px;font-size:12px}.source-disclosure summary{cursor:pointer;list-style:revert;padding:16px 0;font-weight:500}.source-disclosure>p{padding-bottom:14px}.source-links{margin:0 0 20px;padding:0;list-style:none}.source-links>li{margin:12px 0}.source-links a{text-underline-offset:4px;align-items:center;gap:8px;text-decoration:underline;display:inline-flex}.source-links span{color:var(--muted);margin-top:4px;font-size:11px;display:block}.archive-list{margin-top:25px}.archive-list>a{border-bottom:1px solid var(--line);grid-template-columns:55px 1fr 25px;gap:20px;padding:16px 0;display:grid}.archive-list small{color:var(--muted);font-size:12px;display:block}.archive-list strong{font-weight:500}.library-toolbar+.search-field{margin-top:25px}.activity-topline{justify-content:space-between;align-items:center;gap:15px;padding:30px 0 20px;display:flex}.activity-actions{align-items:center;gap:12px;display:flex}.activity-heading{border-bottom:1px solid var(--ink);padding:25px 0 35px}.activity-heading h1{max-width:1050px;margin:19px 0 20px;font-size:clamp(44px,5.5vw,76px)}.activity-heading>p:not(.eyebrow){color:var(--muted);font-size:20px;font-family:var(--serif)}.activity-meta{color:var(--muted);gap:28px;margin-top:28px;font-size:12px;display:flex}.activity-meta>span{align-items:center;gap:8px;display:flex}.activity-layout{grid-template-columns:260px minmax(0,1fr);gap:80px;max-width:1150px;padding-top:38px;display:grid}.activity-sidebar{color:var(--muted);font-size:13px}.activity-sidebar h2{font:25px var(--serif);color:var(--ink)}.activity-sidebar section{border-bottom:1px solid var(--line);margin-bottom:30px;padding-bottom:25px}.activity-sidebar .eyebrow{color:var(--ink);margin-bottom:10px}.materials-list{margin:15px 0 0;padding:0;list-style:none}.materials-list li{padding:6px 0}.materials-list li:before{content:"—";color:#999d91;margin-right:8px}.small-note{margin-bottom:22px;font-size:12px;line-height:1.8}.small-note strong{color:var(--ink);margin-bottom:6px;display:block}.activity-body{min-width:0}.activity-body h2{font-size:37px}.play-steps>.eyebrow{margin-bottom:9px}.play-steps ol{margin:25px 0 30px;padding:0;list-style:none}.play-steps li{border-top:1px solid var(--line);grid-template-columns:33px 1fr;gap:18px;padding:18px 0;display:grid}.play-steps li>span{font:25px var(--serif);color:var(--red);padding-top:4px}.play-steps li>p{font-size:15px;line-height:1.8}.prompt-section{background:var(--yellow);margin:15px 0 37px;padding:27px 30px}.prompt-section .eyebrow{margin-bottom:14px}.prompt-section blockquote{font:27px/1.35 var(--serif);letter-spacing:-.015em;margin:10px 0}.notice-section ul{margin:22px 0;padding-left:20px}.notice-section li{padding:5px 0}.fine-print{color:var(--muted);font-size:11px;line-height:1.7}.variations{border-top:1px solid var(--line);border-bottom:1px solid var(--line);grid-template-columns:1fr 1fr;gap:30px;margin:32px 0;padding:28px 0;display:grid}.variations h3{font:27px var(--serif);margin:9px 0 11px}.variations p:last-child{color:var(--muted);font-size:13px;line-height:1.8}.math-section{margin:35px 0}.math-section h2{margin:9px 0 22px}.math-section>p:not(.eyebrow){font-size:15px;line-height:1.9}.misconception{margin:22px 0;font-size:13px}.misconception>p{color:var(--muted);margin-top:5px;line-height:1.8}.observation-box{background:#eeefe8;margin:35px 0;padding:30px}.observation-box h2{margin:10px 0 15px;font-size:35px}.muted{color:var(--muted)}.observation-box>.muted{font-size:13px}.observation-options{flex-wrap:wrap;gap:9px;margin:22px 0;display:flex}.observation-options .button{gap:7px;padding:8px 13px;font-size:11px}.observation-box label{margin:15px 0 8px;font-size:12px;display:block}textarea{resize:vertical;background:var(--surface);border:1px solid #b6bcb0;border-radius:2px;width:100%;padding:12px;font-size:13px;line-height:1.7}.form-footer{justify-content:space-between;align-items:center;gap:10px;margin-top:12px;display:flex}.save-message{color:#395638;margin-top:10px;font-size:11px}.error-text{color:#a42e20;font-size:12px}.previous-notes{border-top:1px solid var(--line);margin-top:24px;padding-top:20px}.previous-notes h3{font-size:13px;font-weight:600}.previous-notes p{font:20px/1.5 var(--serif);padding-top:15px}.next-section{margin:45px 0}.next-section h2{margin:10px 0;font-size:32px}.next-section>.muted{margin-bottom:22px;font-size:13px}.next-section>a{border-top:1px solid var(--line);font:24px var(--serif);justify-content:space-between;align-items:center;gap:20px;padding:18px 0;display:flex}.next-section>a:hover{color:var(--red)}.next-section small{font:11px var(--sans);color:var(--muted);margin-top:5px;display:block}.article-narrow{max-width:920px;padding-top:30px}.archive-notice{background:var(--yellow);margin-bottom:30px;padding:20px;font-size:13px}.prose{font-size:15px;line-height:1.9}.prose h2{margin:38px 0 20px;font-size:35px}.prose ul,.prose ol{padding-left:23px}.prose li{padding:8px 0}.prose p{margin-bottom:15px}.prose a{text-underline-offset:3px;text-decoration:underline}.notebook-tabs{border-bottom:1px solid var(--line);flex-wrap:wrap;gap:8px;margin-bottom:28px;padding-bottom:20px;display:flex}.notebook-tabs button{border:1px solid var(--line);background:0 0;border-radius:2px;padding:9px 15px;font-size:12px}.notebook-tabs button[aria-pressed=true]{background:var(--green);color:#fff;border-color:var(--green)}.journal-entry{border-bottom:1px solid var(--line);padding:25px 0}.journal-entry>header{justify-content:space-between;align-items:center;gap:20px;display:flex}.journal-entry h2{font-size:28px;line-height:1.2}.journal-entry small{color:var(--muted);margin-bottom:7px;font-size:11px;display:block}.journal-entry .journal-state{background:var(--yellow);white-space:nowrap;padding:4px 9px;font-size:11px}.journal-entry blockquote{font:23px/1.5 var(--serif);margin:18px 0}.journal-entry .text-link{margin-top:12px}.research-intro{border-top:1px solid var(--ink);grid-template-columns:1.2fr .8fr;gap:65px;padding:35px 0 50px;display:grid}.research-intro h2{margin:12px 0 22px;font-size:46px}.research-intro>div>p:not(.eyebrow){color:var(--muted);font-size:15px;line-height:1.9}.evidence-note{background:var(--yellow);align-self:start;padding:28px;font-size:13px;line-height:1.8}.evidence-note h3{font:27px var(--serif);margin-bottom:13px}.research-principles{grid-template-columns:1fr 1fr;gap:25px 55px;margin:0 0 50px;display:grid}.research-principles>section{border-top:1px solid var(--line);padding:23px 0}.research-principles h3{font:28px var(--serif);margin:10px 0 14px}.research-principles p{color:var(--muted);font-size:13px;line-height:1.8}.bibliography{border-top:1px solid var(--ink);padding:35px 0}.bibliography h2{margin-bottom:15px;font-size:40px}.bibliography>p{color:var(--muted);margin-bottom:25px;font-size:13px}.bibliography>ol{margin:0;padding:0;list-style:none}.bibliography li{border-top:1px solid var(--line);grid-template-columns:40px 1fr;gap:18px;padding:22px 0;display:grid}.bibliography li>span{color:var(--red);font:22px var(--serif)}.bibliography a{align-items:center;gap:12px;font-size:16px;font-weight:500;display:inline-flex}.bibliography a:hover{color:var(--red)}.bibliography small{color:var(--muted);margin:5px 0 10px;font-size:11px;display:block}.bibliography li p{color:var(--muted);max-width:850px;font-size:13px}.settings-section{border-top:1px solid var(--line);padding:27px 0}.settings-section h2{margin-bottom:14px;font-size:30px}.settings-section>p{color:var(--muted);margin-bottom:18px;font-size:13px}.settings-actions{flex-wrap:wrap;gap:10px;display:flex}.settings-section label{cursor:pointer;align-items:center;gap:12px;font-size:14px;display:flex}.settings-section input[type=checkbox]{accent-color:var(--green);width:18px;height:18px}.settings-section .status-text{margin-top:14px;font-size:12px}.confirm-import{background:var(--yellow);margin-top:20px;padding:20px;font-size:13px}.confirm-import p{margin-bottom:15px}.settings-page{max-width:930px}.h-display,.h-title{font-family:var(--serif)}.btn{background:var(--green);color:#fff;border-radius:2px;align-items:center;gap:10px;padding:12px 20px;display:inline-flex}.inline-link{text-decoration:underline}.sr-only{clip:rect(0, 0, 0, 0);white-space:nowrap;border:0;width:1px;height:1px;margin:-1px;padding:0;position:absolute;overflow:hidden}@media (width>=1450px){.hero-figure img{height:515px}}@media (width<=1050px){.header-inner{gap:25px;padding:0 32px}.site-header nav{gap:23px}.header-map{display:none}.home-page,.page-wrap{padding-left:32px;padding-right:32px}.hero{gap:35px}.hero h1{font-size:65px}.hero-figure img{height:445px}.hero-footnote{max-width:250px;line-height:1.8}.hero-figure figcaption span:last-child{display:none}.principle-band{grid-template-columns:1fr 1fr;margin:0 -32px;padding:38px 32px}.principle-band>.eyebrow{grid-column:1/-1}.site-footer{padding-left:32px;padding-right:32px}.library-layout{grid-template-columns:190px 1fr;gap:28px}.sidebar-name{margin-left:6px;font-size:11px}.activity-layout{grid-template-columns:220px 1fr;gap:42px}.observation-box{padding:24px}.trajectory-grid{gap:13px}.research-intro{gap:35px}}@media (width<=760px){.header-inner{flex-wrap:wrap;justify-content:center;gap:15px;height:auto;min-height:112px;padding:21px 22px 0}.wordmark{font-size:34px}.site-header nav{justify-content:center;gap:28px;width:100%;margin:0;font-size:12px}.site-header nav a{white-space:nowrap;padding:5px 0 15px}.home-page,.page-wrap{padding-left:23px;padding-right:23px}.hero{flex-direction:column;align-items:stretch;gap:30px;padding:35px 0;display:flex}.hero h1{max-width:470px;margin:19px 0;font-size:58px;line-height:.97}.hero-description{max-width:400px;margin-bottom:22px;font-size:14px}.hero-footnote{max-width:none;font-size:9px}.hero-figure img{aspect-ratio:1.48;-o-object-fit:cover;object-fit:cover;height:auto}.hero-figure figcaption{font-size:9px}.hero-figure figcaption span:last-child{display:inline}.section-heading{align-items:start;gap:20px;margin-bottom:26px}.section-heading h2{font-size:36px}.section-heading>p{display:none}.section-heading>.text-link{max-width:135px;margin-top:24px;font-size:11px}.strand-section{padding:30px 0}.strand-grid{grid-template-columns:1fr;gap:0}.strand-link{grid-template-columns:29px 1fr 22px;gap:13px;padding:21px 0}.strand-link:nth-last-child(2){border-bottom:0}.strand-link h3{font-size:26px}.strand-link p:last-child{font-size:11px}.strand-number{font-size:25px}.starting-section{padding:25px 0 40px}.guide-row{grid-template-columns:24px minmax(0,1fr) 40px;gap:12px;padding:22px 0}.guide-row h3{font-size:25px}.guide-row p{font-size:12px}.meta{gap:10px;font-size:9px}.row-time,.row-arrow{display:none}.row-mobile-meta{color:var(--muted);margin-top:9px;font-size:10px;display:block}.principle-band{margin:0 -23px;padding:30px 23px;display:block}.principle-band h2{margin:18px 0 22px;font-size:42px}.principle-band>div>p{font-size:13px}.site-footer{padding:35px 23px 24px}.footer-top{flex-wrap:wrap;justify-content:start;gap:20px}.footer-top .wordmark{font-size:30px}.footer-top>p{font-size:20px}.footer-top>a:last-child{width:100%;font-size:11px}.footer-bottom{font-size:9px;line-height:1.9;display:block}.footer-bottom>span{display:block}.page-heading{padding:35px 0 29px}.page-heading h1{font-size:48px;line-height:1}.page-heading>p:last-child{font-size:14px}.library-toolbar{align-items:start;gap:15px}.view-switch button{gap:6px;padding:9px 10px;font-size:11px}.library-toolbar>.small-link{max-width:90px;font-size:10px;line-height:1.5}.library-layout{margin-top:24px;display:block}.library-sidebar{gap:7px;margin-bottom:25px;padding-bottom:10px;display:flex;overflow-x:auto}.library-sidebar>.eyebrow,.sidebar-note{display:none}.library-sidebar>button{white-space:nowrap;border:1px solid var(--line);border-radius:2px;flex-shrink:0;gap:10px;width:auto;padding:10px}.sidebar-name{font-size:11px}.library-sidebar>button>span:last-child{display:none}.library-results .guide-row{grid-template-columns:22px minmax(0,1fr) 40px;gap:10px}.filter-row{align-items:end;gap:10px}.filter-row>label:first-child{flex-direction:column;align-items:start;gap:5px;display:flex}.quick-filter{gap:5px;padding-bottom:10px;font-size:10px}select{padding-right:20px;font-size:11px}.search-field input{font-size:12px}.map-explainer{padding:20px;font-size:12px}.learning-strand>header{gap:15px}.learning-strand h2{font-size:31px}.learning-strand>header>span{font-size:30px}.trajectory-grid{grid-template-columns:1fr;gap:25px}.trajectory-grid h3{min-height:0;margin:10px 0;font-size:24px}.stage-label{border-top-width:1px}.trajectory-grid a{font-size:13px}.trajectory-grid>div:last-child .stage-label>svg{display:block}.activity-topline{padding:20px 0 12px}.activity-topline>.text-link{gap:6px;font-size:11px}.activity-actions{gap:4px}.activity-actions .button{gap:8px;padding:9px 10px;font-size:11px}.activity-heading{padding:20px 0 27px}.activity-heading h1{font-size:51px;line-height:1.02}.activity-heading>p:not(.eyebrow){font-size:21px}.activity-meta{flex-wrap:wrap;gap:14px;font-size:10px}.activity-layout{flex-direction:column;gap:24px;padding-top:25px;display:flex}.activity-sidebar{grid-template-columns:1fr 1fr;gap:20px;font-size:12px;display:grid}.activity-sidebar section{margin-bottom:0;padding-bottom:16px}.activity-sidebar h2{font-size:23px}.activity-sidebar>.small-note,.activity-sidebar>.fine-print{grid-column:1/-1;margin:0;font-size:11px}.activity-body h2{font-size:33px}.play-steps li{grid-template-columns:28px 1fr;gap:12px}.play-steps li>p{font-size:14px}.prompt-section{padding:24px}.prompt-section blockquote{font-size:26px}.notice-section li{font-size:14px}.variations{gap:24px}.variations .eyebrow{font-size:9px}.variations h3{font-size:24px}.variations p:last-child{font-size:12px}.observation-box{margin:30px -8px;padding:22px}.observation-options{gap:6px}.observation-options .button{min-height:42px;padding:7px 10px;font-size:10px}.form-footer .button{padding:10px 13px;font-size:11px}.research-intro{grid-template-columns:1fr;gap:28px}.research-intro h2{font-size:39px}.research-principles{grid-template-columns:1fr;gap:0}.bibliography a{font-size:14px}.bibliography li{grid-template-columns:25px 1fr;gap:12px}.bibliography li p{font-size:12px}.journal-entry>header{align-items:start}.journal-entry h2{font-size:26px}.journal-entry .journal-state{font-size:9px}.journal-entry blockquote{font-size:21px}}@media (width<=360px){.home-page,.page-wrap{padding-left:18px;padding-right:18px}.hero h1{font-size:50px}.site-header nav{gap:14px}.hero-figure figcaption span:last-child{display:none}.activity-heading h1{font-size:43px}.activity-topline{flex-wrap:wrap}.variations{grid-template-columns:1fr}.observation-options{flex-direction:column}.principle-band{margin-left:-18px;margin-right:-18px}.filter-row{flex-direction:column;align-items:start}.activity-sidebar{grid-template-columns:1fr}}@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,:before,:after{transition:none!important;animation:none!important}}html[data-reduced-motion=true]{scroll-behavior:auto}html[data-reduced-motion=true] *,html[data-reduced-motion=true] :before,html[data-reduced-motion=true] :after{transition:none!important;animation:none!important}@media print{body{background:#fff;font-size:11pt}.site-header,.site-footer,.skip-link,.activity-topline,.observation-box,.next-section,.source-disclosure{display:none!important}.page-wrap{max-width:none;padding:0!important}.activity-heading{padding-top:0}.activity-heading h1{font-size:34pt}.activity-layout{padding-top:20px;display:block}.activity-sidebar{display:block}.activity-sidebar section{margin-bottom:15px;padding-bottom:10px}.activity-sidebar .small-note,.activity-sidebar .fine-print{font-size:9pt}.activity-body h2{font-size:22pt}.play-steps li,.variations>div,.notice-section,.prompt-section,.math-section{-moz-column-break-inside:avoid;break-inside:avoid}.play-steps li>p,.math-section>p:not(.eyebrow){font-size:11pt;line-height:1.5}.prompt-section{background:0 0;border:1px solid #999}.prompt-section blockquote{font-size:17pt}.variations p:last-child{font-size:10pt}.activity-heading>p:not(.eyebrow){font-size:15pt}.activity-meta{font-size:9pt}a{text-decoration:none}}