:root{
  --sn-navy:#172554;--sn-blue:#2563eb;--sn-blue-2:#1d4ed8;
  --sn-gold:#f59e0b;--sn-bg:#eef4ff;--sn-surface:#fff;--sn-text:#172033;
  --sn-muted:#526078;--sn-border:#c8d7f2;--sn-shadow:0 14px 34px rgba(23,37,84,.13);
  --sn-radius:20px;--sn-reading:880px;--sn-shell:1180px;
}
html{scroll-behavior:smooth;background:var(--sn-bg)}
body{background:var(--page,var(--page-background,var(--sn-bg)))!important;color:var(--text,var(--sn-text))!important;line-height:1.65}
body::before{content:"";position:fixed;inset:0;pointer-events:none;z-index:-1;background:radial-gradient(circle at 8% 8%,color-mix(in srgb,var(--accent,var(--sn-blue)) 12%,transparent),transparent 26%),radial-gradient(circle at 92% 18%,color-mix(in srgb,var(--yellow-border,var(--sn-gold)) 8%,transparent),transparent 24%)}
header,.site-header,.navbar,nav.top-nav{box-shadow:0 8px 26px rgba(23,37,84,.13)}
main,.main-content,.page-content,.lesson-page,.topic-page{width:min(calc(100% - 32px),var(--sn-shell));margin-inline:auto}
.lesson-content,.lesson-container,.content-container,article,.worksheet-paper,.paper{max-width:var(--sn-reading);margin-inline:auto}
.card,.lesson-card,.topic-card,.feature-card,.resource-card,.practice-card,.quiz-card,.example,.worked-example,.info-box,.tip-box,.warning-box,.summary-box,.checkpoint,.section-card,.content-card,.worksheet-card{
  background:var(--card,rgba(255,255,255,.97))!important;border:1px solid var(--border,var(--sn-border))!important;border-radius:var(--sn-radius)!important;box-shadow:var(--sn-shadow)!important;color:var(--text,var(--sn-text))!important
}
.card,.lesson-card,.topic-card,.feature-card,.resource-card,.practice-card,.quiz-card,.section-card,.content-card,.worksheet-card{transition:transform .2s ease,box-shadow .2s ease,border-color .2s ease}
.card:hover,.lesson-card:hover,.topic-card:hover,.feature-card:hover,.resource-card:hover,.worksheet-card:hover{transform:translateY(-4px);box-shadow:0 20px 42px rgba(23,37,84,.18)!important;border-color:#93b4ed!important}
h1,h2,h3,h4{color:var(--navy,var(--sn-navy))!important;letter-spacing:-.02em}
p,li,label,input,textarea,select{color:var(--text,var(--sn-text))}
small,.muted,.subtitle,.description{color:var(--muted,var(--sn-muted))!important}
button,.btn,a.button,.primary-btn,.cta-button,.start-btn,.nav-button,.print-button{min-height:46px;border-radius:14px!important;font-weight:800!important;box-shadow:0 8px 18px rgba(37,99,235,.18);transition:transform .18s ease,filter .18s ease,box-shadow .18s ease}
button:hover,.btn:hover,a.button:hover,.primary-btn:hover,.cta-button:hover,.start-btn:hover,.nav-button:hover,.print-button:hover{transform:translateY(-2px);filter:saturate(1.12);box-shadow:0 12px 24px rgba(37,99,235,.24)}
input,textarea,select{background:#fff!important;border:2px solid #b8cae9!important;border-radius:12px!important;padding:.72rem .85rem!important}
.hero,.page-hero,.topic-hero,.lesson-hero,.welcome-section{border-radius:24px!important;box-shadow:0 18px 42px rgba(23,37,84,.20)!important;overflow:hidden}
section{scroll-margin-top:90px}
.sn31-progress{position:fixed;inset:0 0 auto 0;height:4px;background:transparent;z-index:9998}.sn31-progress span{display:block;height:100%;width:0;background:linear-gradient(90deg,var(--accent,var(--sn-blue)),var(--navy,var(--sn-navy)),var(--yellow-border,var(--sn-gold)));box-shadow:0 1px 8px rgba(37,99,235,.45)}
.sn31-scroll{position:fixed;right:18px;bottom:20px;display:grid;gap:10px;z-index:9997}.sn31-scroll button{width:48px;height:48px;min-height:48px;border:0;border-radius:50%!important;background:var(--sn-navy);color:white;font-size:20px;cursor:pointer}.sn31-scroll button:last-child{background:var(--sn-blue)}
.sn31-toc-toggle{position:fixed;left:18px;bottom:20px;z-index:9997;border:0!important;background:var(--sn-navy)!important;color:#fff!important;padding:0 16px!important}
.sn31-toc{position:fixed;left:18px;top:96px;width:260px;max-height:calc(100vh - 150px);overflow:auto;background:#fff;border:1px solid var(--sn-border);border-radius:18px;box-shadow:var(--sn-shadow);padding:14px;z-index:9996;transform:translateX(-120%);transition:transform .25s ease}.sn31-toc.open{transform:translateX(0)}
.sn31-toc strong{display:block;color:var(--sn-navy);margin:2px 4px 10px}.sn31-toc a{display:block;padding:8px 10px;margin:3px 0;border-radius:10px;color:#334155;text-decoration:none;font-weight:700;font-size:.9rem}.sn31-toc a:hover,.sn31-toc a.active{background:#e8f0ff;color:var(--sn-blue-2)}
@media(min-width:801px){.sn31-toc,.sn31-toc-toggle{display:none!important}}
@media(max-width:800px){main,.main-content,.page-content,.lesson-page,.topic-page{width:min(calc(100% - 20px),var(--sn-shell))}.card,.lesson-card,.topic-card,.feature-card,.resource-card,.practice-card,.quiz-card,.section-card,.content-card,.worksheet-card{border-radius:17px!important;box-shadow:0 10px 25px rgba(23,37,84,.14)!important}.sn31-scroll{right:12px;bottom:14px}.sn31-toc-toggle{left:12px;bottom:14px}.sn31-toc{left:12px;right:12px;top:auto;bottom:76px;width:auto;max-height:62vh}.hero,.page-hero,.topic-hero,.lesson-hero,.welcome-section{border-radius:19px!important}}
/* Shared animation polish */
.sn31-page-shell{opacity:1;transform:none}
.sn31-page-shell.sn31-page-animate{opacity:0;transform:translateY(10px)}
.sn31-page-shell.sn31-page-ready{opacity:1;transform:none;transition:opacity .45s cubic-bezier(.2,.8,.2,1),transform .45s cubic-bezier(.2,.8,.2,1);will-change:opacity,transform}

.sn31-reveal{opacity:1;transform:none;transition:opacity .42s cubic-bezier(.2,.8,.2,1),transform .42s cubic-bezier(.2,.8,.2,1);will-change:opacity,transform}
.sn31-reveal.sn31-animate{opacity:0;transform:translateY(12px)}
.sn31-reveal.sn31-visible{opacity:1;transform:none}

.card,.lesson-card,.topic-card,.feature-card,.resource-card,.practice-card,.quiz-card,.section-card,.content-card,.worksheet-card,.path-card,.learning-card{transform:translateY(0) scale(1);will-change:transform,box-shadow}
.card:hover,.lesson-card:hover,.topic-card:hover,.feature-card:hover,.resource-card:hover,.worksheet-card:hover,.path-card:hover,.learning-card:hover,.section-card:hover,.practice-card:hover,.quiz-card:hover,.content-card:hover{transform:translateY(-4px) scale(1.01);box-shadow:0 20px 42px rgba(23,37,84,.18)!important;border-color:#93b4ed!important}
.card:focus-visible,.lesson-card:focus-visible,.topic-card:focus-visible,.feature-card:focus-visible,.resource-card:focus-visible,.practice-card:focus-visible,.quiz-card:focus-visible,.section-card:focus-visible,.content-card:focus-visible,.worksheet-card:focus-visible,.path-card:focus-visible,.learning-card:focus-visible{transform:translateY(-2px) scale(1.01);outline:none}

button,.btn,a.button,.primary-btn,.cta-button,.start-btn,.nav-button,.print-button,.path-card,.lesson-card,.topic-card{transition:transform .2s cubic-bezier(.2,.8,.2,1),filter .2s cubic-bezier(.2,.8,.2,1),box-shadow .2s cubic-bezier(.2,.8,.2,1),opacity .2s ease}
button:hover,.btn:hover,a.button:hover,.primary-btn:hover,.cta-button:hover,.start-btn:hover,.nav-button:hover,.print-button:hover{transform:translateY(-2px) scale(1.01);filter:saturate(1.12);box-shadow:0 12px 24px rgba(37,99,235,.24)}

.progress-fill,.ws-progress-fill,[role="progressbar"],[aria-valuenow]{width:0!important;transition:width .55s cubic-bezier(.2,.8,.2,1)}

details > *:not(summary){transition:max-height .28s cubic-bezier(.2,.8,.2,1),opacity .28s cubic-bezier(.2,.8,.2,1),padding .28s ease,margin .28s ease}
details > .sn31-details-panel{overflow:hidden;max-height:0;opacity:0;padding-top:0!important;padding-bottom:0!important;margin-top:0!important;margin-bottom:0!important}
details[open] > .sn31-details-panel{max-height:1400px;opacity:1;padding-top:inherit!important;padding-bottom:inherit!important;margin-top:inherit!important;margin-bottom:inherit!important}

.answers-content,.hint-box,.hint-content,.solution-box,.solution-content,.worked-solution,.accordion-panel,.collapsible{overflow:hidden;transition:max-height .28s cubic-bezier(.2,.8,.2,1),opacity .28s cubic-bezier(.2,.8,.2,1),transform .28s cubic-bezier(.2,.8,.2,1)}
.answers-content:not(.sn31-open),.hint-box:not(.sn31-open),.hint-content:not(.sn31-open),.solution-box:not(.sn31-open),.solution-content:not(.sn31-open),.worked-solution:not(.sn31-open),.accordion-panel:not(.sn31-open),.collapsible:not(.sn31-open){max-height:0!important;opacity:0;transform:translateY(-3px)}
.answers-content.sn31-open,.hint-box.sn31-open,.hint-content.sn31-open,.solution-box.sn31-open,.solution-content.sn31-open,.worked-solution.sn31-open,.accordion-panel.sn31-open,.collapsible.sn31-open{max-height:1400px!important;opacity:1;transform:none}

@media (prefers-reduced-motion: reduce){*,*::before,*::after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important;scroll-behavior:auto!important}.sn31-page-shell.sn31-page-animate,.sn31-reveal.sn31-animate{opacity:1!important;transform:none!important}.sn31-page-shell.sn31-page-ready,.sn31-reveal.sn31-visible{transition:none!important}.progress-fill,.ws-progress-fill,[role="progressbar"],[aria-valuenow]{transition:none!important;width:auto!important}} 

@media print{.sn31-progress,.sn31-scroll,.sn31-toc,.sn31-toc-toggle{display:none!important}body{background:#fff!important}body::before{display:none}.card,.worksheet-paper,.paper{box-shadow:none!important}}