:root{
  --bg:#fff9fc;
  --surface:#ffffff;
  --surface-2:#fff0f6;
  --text:#243047;
  --muted:#657086;
  --primary:#c54d86;
  --primary-strong:#96305f;
  --secondary:#7d6dd8;
  --accent:#f5b94c;
  --good:#2f8f68;
  --danger:#c64c55;
  --line:#eadde5;
  --shadow:0 12px 32px rgba(101,70,91,.10);
  --radius:20px;
  --header-grad:linear-gradient(135deg,#fff1f7,#f4efff);
}
:root[data-theme="sky"]{
  --bg:#f5fbff;
  --surface:#ffffff;
  --surface-2:#eaf7ff;
  --text:#17324d;
  --muted:#5d7186;
  --primary:#2c87c8;
  --primary-strong:#1d5f92;
  --secondary:#1b9a93;
  --accent:#f0a63b;
  --good:#2e8a64;
  --danger:#c34d56;
  --line:#d9e9f3;
  --shadow:0 12px 32px rgba(35,84,115,.10);
  --header-grad:linear-gradient(135deg,#eaf7ff,#eefcf8);
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;background:var(--bg);color:var(--text);font-family:Inter,ui-sans-serif,system-ui,-apple-system,"Segoe UI",Arial,sans-serif;line-height:1.65;font-size:17px}
a{color:var(--primary-strong);text-decoration:none}
a:hover{text-decoration:underline}
button,input,select,textarea{font:inherit}
button{cursor:pointer}
img,svg{max-width:100%}
.skip-link{position:absolute;left:-999px;top:0;background:var(--text);color:white;padding:10px;z-index:9999}.skip-link:focus{left:10px;top:10px}
.site-header{position:sticky;top:0;z-index:30;background:rgba(255,255,255,.96);backdrop-filter:blur(14px);border-bottom:1px solid var(--line)}
.header-inner{max-width:1200px;margin:auto;padding:10px 18px;display:grid;grid-template-columns:auto 1fr auto;gap:18px;align-items:center}
.brand{display:flex;gap:12px;align-items:center;color:var(--text);font-weight:800;white-space:nowrap}
.brand-mark{width:42px;height:42px;border-radius:14px;display:grid;place-items:center;background:var(--header-grad);border:1px solid var(--line);font-size:22px}
.brand small{display:block;color:var(--muted);font-weight:600;font-size:12px;line-height:1.2}
.main-nav{display:flex;gap:4px;justify-content:center;flex-wrap:wrap}
.main-nav a{padding:9px 11px;border-radius:12px;color:var(--text);font-weight:650;font-size:14px}
.main-nav a:hover,.main-nav a.active{background:var(--surface-2);text-decoration:none;color:var(--primary-strong)}
.header-actions{display:flex;align-items:center;gap:8px}
.theme-choice{display:flex;background:var(--surface-2);border:1px solid var(--line);padding:3px;border-radius:999px}
.theme-choice button{border:0;background:transparent;color:var(--text);padding:7px 10px;border-radius:999px;font-size:13px;font-weight:700}
.theme-choice button.active{background:var(--surface);box-shadow:0 3px 10px rgba(0,0,0,.08);color:var(--primary-strong)}
.mobile-menu-btn{display:none;border:1px solid var(--line);background:var(--surface);border-radius:12px;padding:8px 10px}
.hero{background:var(--header-grad);border-bottom:1px solid var(--line)}
.hero-inner{max-width:1200px;margin:auto;padding:64px 20px;display:grid;grid-template-columns:1.2fr .8fr;gap:40px;align-items:center}
.eyebrow{display:inline-flex;align-items:center;gap:8px;background:var(--surface);border:1px solid var(--line);border-radius:999px;padding:7px 12px;font-weight:750;color:var(--primary-strong);font-size:14px}
h1{font-size:clamp(36px,6vw,68px);line-height:1.05;margin:18px 0 16px;letter-spacing:-.035em}
h2{font-size:clamp(27px,4vw,40px);line-height:1.15;margin:0 0 18px;letter-spacing:-.02em}
h3{font-size:22px;line-height:1.25;margin:0 0 12px}
.lead{font-size:20px;color:var(--muted);max-width:720px}
.cta-row{display:flex;gap:12px;flex-wrap:wrap;margin-top:26px}
.btn{border:0;border-radius:14px;padding:12px 17px;font-weight:780;display:inline-flex;align-items:center;justify-content:center;gap:8px;text-decoration:none}
.btn:hover{text-decoration:none;transform:translateY(-1px)}
.btn-primary{background:var(--primary);color:#fff}.btn-primary:hover{background:var(--primary-strong)}
.btn-secondary{background:var(--surface);color:var(--text);border:1px solid var(--line)}
.btn-ghost{background:transparent;color:var(--primary-strong);border:1px dashed var(--primary)}
.btn-danger{background:#fff1f2;color:var(--danger);border:1px solid #f2c7cb}
.hero-visual{background:var(--surface);border:1px solid var(--line);border-radius:28px;padding:22px;box-shadow:var(--shadow)}
.number-art{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}.number-art div{aspect-ratio:1;border-radius:18px;background:var(--surface-2);display:grid;place-items:center;font-weight:900;font-size:28px;color:var(--primary-strong);border:1px solid var(--line)}
.container{max-width:1200px;margin:auto;padding:44px 20px}
.section-head{display:flex;align-items:end;justify-content:space-between;gap:20px;margin-bottom:22px}.section-head p{margin:0;color:var(--muted);max-width:680px}
.grid{display:grid;gap:18px}.grid-3{grid-template-columns:repeat(3,1fr)}.grid-2{grid-template-columns:repeat(2,1fr)}.grid-4{grid-template-columns:repeat(4,1fr)}
.card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:22px;box-shadow:var(--shadow)}
.card.soft{background:var(--surface-2);box-shadow:none}
.topic-card{display:flex;flex-direction:column;min-height:230px}.topic-card .icon{width:52px;height:52px;border-radius:17px;background:var(--surface-2);display:grid;place-items:center;font-size:25px;margin-bottom:18px}.topic-card p{color:var(--muted);margin:0 0 18px}.topic-card .meta{margin-top:auto;display:flex;justify-content:space-between;align-items:center;font-size:13px;color:var(--muted)}
.progress-track{height:10px;background:var(--surface-2);border-radius:999px;overflow:hidden;border:1px solid var(--line)}.progress-fill{height:100%;background:linear-gradient(90deg,var(--primary),var(--secondary));width:0;transition:width .4s ease}
.kpi{background:var(--surface);border:1px solid var(--line);border-radius:18px;padding:18px}.kpi strong{display:block;font-size:30px;color:var(--primary-strong)}.kpi span{color:var(--muted);font-size:14px}
.page-hero{background:var(--header-grad);border-bottom:1px solid var(--line)}.page-hero .container{padding-top:38px;padding-bottom:38px}.page-hero h1{font-size:clamp(34px,5vw,52px);margin:8px 0 10px}.breadcrumbs{font-size:14px;color:var(--muted)}
.lesson-layout{display:grid;grid-template-columns:280px 1fr;gap:24px;align-items:start}.lesson-sidebar{position:sticky;top:92px}.lesson-nav{display:flex;flex-direction:column;gap:7px}.lesson-nav a{display:flex;justify-content:space-between;gap:12px;padding:10px 12px;border-radius:12px;color:var(--text);font-size:14px}.lesson-nav a:hover,.lesson-nav a.active{background:var(--surface-2);text-decoration:none;color:var(--primary-strong)}
.lesson-content{min-width:0}.lesson-block{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:26px;margin-bottom:18px;box-shadow:var(--shadow)}.lesson-block h2{font-size:31px}.lesson-block h3{margin-top:20px}.lesson-block ul{padding-left:22px}.lesson-meta{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:18px}.chip{display:inline-flex;align-items:center;gap:6px;border:1px solid var(--line);background:var(--surface-2);border-radius:999px;padding:6px 10px;font-size:13px;font-weight:700}
.math-box{background:#fffdf7;border:1px solid #f1dfac;border-left:5px solid var(--accent);border-radius:15px;padding:16px 18px;margin:16px 0;font-family:"Cambria Math",Georgia,serif;font-size:20px;overflow:auto}
:root[data-theme="sky"] .math-box{background:#fbfeff;border-color:#cfe7f6}
.callout{border-radius:15px;padding:16px 18px;margin:16px 0;border:1px solid var(--line)}.callout.good{background:#eefaf4;border-color:#c8ead8}.callout.warn{background:#fff8e7;border-color:#f0d79a}.callout.info{background:var(--surface-2)}
.step-list{counter-reset:step;display:grid;gap:12px}.step{display:grid;grid-template-columns:42px 1fr;gap:12px;align-items:start}.step::before{counter-increment:step;content:counter(step);width:36px;height:36px;border-radius:12px;background:var(--primary);color:#fff;display:grid;place-items:center;font-weight:850}.step p{margin:3px 0 0}
.visual-grid{display:grid;grid-template-columns:repeat(auto-fit,minmax(70px,1fr));gap:8px;margin:14px 0}.visual-cell{border:1px solid var(--line);background:var(--surface-2);border-radius:12px;padding:12px;text-align:center;min-height:70px}.visual-cell strong{display:block;color:var(--primary-strong);font-size:22px}.visual-cell small{color:var(--muted)}
.tool-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.tool-panel{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:22px;box-shadow:var(--shadow)}.tool-panel.full{grid-column:1/-1}.form-row{display:flex;gap:10px;align-items:end;flex-wrap:wrap}.field{display:grid;gap:6px;flex:1;min-width:150px}.field label{font-weight:750;font-size:14px}.field input,.field select{width:100%;border:1px solid var(--line);border-radius:12px;padding:11px 12px;background:var(--surface);color:var(--text)}.field input:focus,.field select:focus{outline:3px solid color-mix(in srgb,var(--primary) 22%, transparent);border-color:var(--primary)}
.result{margin-top:14px;padding:15px;border-radius:14px;background:var(--surface-2);border:1px solid var(--line);min-height:58px}.result.good{background:#eefaf4;border-color:#c8ead8}.result.bad{background:#fff0f1;border-color:#efc3c7}
.sieve{display:grid;grid-template-columns:repeat(10,1fr);gap:6px;margin-top:15px}.sieve button{aspect-ratio:1;border:1px solid var(--line);background:var(--surface);border-radius:10px;color:var(--text);font-weight:700}.sieve button.crossed{text-decoration:line-through;background:#f2f2f2;color:#9a9a9a}.sieve button.prime{background:#eaf8f2;border-color:#acd9c4;color:#1d7452}
.quiz-shell{display:grid;grid-template-columns:230px 1fr;gap:20px}.quiz-side{position:sticky;top:92px}.question-card{background:var(--surface);border:1px solid var(--line);border-radius:var(--radius);padding:24px;box-shadow:var(--shadow)}.question-number{color:var(--muted);font-weight:700;font-size:14px}.question-text{font-size:24px;font-weight:800;margin:8px 0 18px}.options{display:grid;gap:10px}.option{display:flex;gap:10px;align-items:center;border:1px solid var(--line);border-radius:14px;padding:12px;background:var(--surface)}.option:hover{background:var(--surface-2)}.feedback{margin-top:14px;padding:14px;border-radius:13px;display:none}.feedback.show{display:block}.feedback.good{background:#eefaf4;color:#1d6d4e}.feedback.bad{background:#fff0f1;color:#9b3039}.quiz-controls{display:flex;justify-content:space-between;gap:10px;margin-top:18px}
.pattern-stage{display:flex;align-items:flex-end;gap:10px;min-height:150px;padding:18px;background:var(--surface-2);border-radius:16px;overflow:auto}.dot{width:14px;height:14px;border-radius:50%;background:var(--primary);display:inline-block;margin:3px}.dot-grid{display:grid;gap:4px;justify-content:start}.machine{display:grid;grid-template-columns:1fr auto 1fr;gap:14px;align-items:center}.machine-box{background:var(--surface-2);border:2px dashed var(--primary);padding:25px;border-radius:20px;text-align:center;font-size:24px;font-weight:850}.machine-arrow{font-size:34px;color:var(--primary)}
.puzzle-board{position:relative;max-width:430px;margin:20px auto;aspect-ratio:1.15}.node{position:absolute;width:52px;height:52px;border-radius:50%;border:2px solid var(--primary);background:var(--surface);display:grid;place-items:center}.node input{width:44px;height:44px;text-align:center;border:0;background:transparent;font-weight:850;color:var(--text)}.node input:focus{outline:3px solid color-mix(in srgb,var(--primary) 25%,transparent);border-radius:50%}.puzzle-lines{position:absolute;inset:0;width:100%;height:100%;z-index:-1}.puzzle-lines line,.puzzle-lines polygon{stroke:var(--secondary);stroke-width:4;fill:none}
.flashcard{min-height:220px;display:grid;place-items:center;text-align:center;cursor:pointer;perspective:1000px}.flash-inner{position:relative;width:100%;height:220px;transition:transform .5s;transform-style:preserve-3d}.flashcard.flipped .flash-inner{transform:rotateY(180deg)}.flash-front,.flash-back{position:absolute;inset:0;backface-visibility:hidden;border:1px solid var(--line);border-radius:var(--radius);padding:24px;display:grid;place-items:center;background:var(--surface);box-shadow:var(--shadow)}.flash-back{transform:rotateY(180deg);background:var(--surface-2)}
.table-wrap{overflow:auto;border:1px solid var(--line);border-radius:15px}table{width:100%;border-collapse:collapse;background:var(--surface)}th,td{padding:12px 14px;border-bottom:1px solid var(--line);text-align:left}th{background:var(--surface-2)}
.empty-state{text-align:center;padding:40px;color:var(--muted)}
.site-footer{margin-top:50px;background:var(--surface);border-top:1px solid var(--line)}.footer-grid{max-width:1200px;margin:auto;padding:38px 20px;display:grid;grid-template-columns:1.3fr 1fr 1fr;gap:30px}.footer-grid p,.footer-grid li{color:var(--muted);font-size:14px}.footer-grid ul{list-style:none;padding:0}.footer-bottom{border-top:1px solid var(--line);padding:15px 20px;text-align:center;color:var(--muted);font-size:13px}
.toast{position:fixed;right:18px;bottom:18px;background:var(--text);color:#fff;padding:12px 16px;border-radius:13px;box-shadow:var(--shadow);opacity:0;transform:translateY(15px);pointer-events:none;transition:.25s;z-index:100}.toast.show{opacity:1;transform:translateY(0)}
.mobile-bottom{display:none}
@media(max-width:980px){.header-inner{grid-template-columns:1fr auto}.main-nav{display:none;grid-column:1/-1;justify-content:flex-start;padding-top:6px}.main-nav.open{display:flex}.mobile-menu-btn{display:block}.hero-inner{grid-template-columns:1fr}.hero-visual{max-width:600px}.grid-4{grid-template-columns:repeat(2,1fr)}.grid-3{grid-template-columns:repeat(2,1fr)}.lesson-layout{grid-template-columns:1fr}.lesson-sidebar{position:static}.lesson-nav{display:grid;grid-template-columns:repeat(3,1fr)}.quiz-shell{grid-template-columns:1fr}.quiz-side{position:static}.footer-grid{grid-template-columns:1fr 1fr}.tool-grid{grid-template-columns:1fr}.tool-panel.full{grid-column:auto}}
@media(max-width:680px){body{font-size:16px;padding-bottom:68px}.header-inner{padding:8px 12px}.brand span{display:none}.theme-choice button{padding:6px 8px}.hero-inner{padding:42px 16px}.container{padding:34px 16px}.grid-3,.grid-2,.grid-4{grid-template-columns:1fr}.section-head{align-items:start;flex-direction:column}.lesson-nav{grid-template-columns:1fr 1fr}.lesson-block{padding:20px}.lesson-block h2{font-size:27px}.main-nav{max-height:60vh;overflow:auto}.footer-grid{grid-template-columns:1fr}.mobile-bottom{display:grid;grid-template-columns:repeat(4,1fr);position:fixed;left:0;right:0;bottom:0;z-index:35;background:rgba(255,255,255,.97);border-top:1px solid var(--line);padding:7px 6px}.mobile-bottom a{display:grid;place-items:center;gap:2px;font-size:11px;color:var(--muted);padding:4px}.mobile-bottom a.active{color:var(--primary-strong);font-weight:800}.mobile-bottom b{font-size:20px}.sieve{grid-template-columns:repeat(5,1fr)}.machine{grid-template-columns:1fr}.machine-arrow{transform:rotate(90deg);text-align:center}.puzzle-board{max-width:350px}.node{width:45px;height:45px}.node input{width:38px;height:38px}.quiz-controls{flex-direction:column}.quiz-controls .btn{width:100%}}
@media print{.site-header,.mobile-bottom,.site-footer,.btn,.theme-choice,.page-hero{display:none!important}body{background:#fff;color:#000;padding:0}.container{max-width:none;padding:0}.card,.lesson-block,.tool-panel{box-shadow:none;border:1px solid #ccc;break-inside:avoid}}