:root{--accent:#605cf4;--soft:#f4f3ff;--ink:#171923;--muted:#617087;--line:#e5e8ef}*{box-sizing:border-box}body{margin:0;color:var(--ink);font:16px/1.7 Inter,system-ui,-apple-system,"Segoe UI",sans-serif}.wrap{width:min(1080px,calc(100% - 40px));margin:auto}.top{border-bottom:1px solid var(--line);background:#fff}.top .wrap{height:70px;display:flex;justify-content:space-between;align-items:center;gap:18px}.brand{font-size:1.25rem;font-weight:850;color:var(--ink);text-decoration:none}.brand span{color:var(--accent)}.top nav{display:flex;gap:22px}.top nav a{color:var(--muted);text-decoration:none;font-size:.9rem}.crumb{padding:25px 0 10px;color:#8b95a6;font-size:.9rem}.crumb a{color:var(--accent);text-decoration:none}.layout{display:grid;grid-template-columns:minmax(0,720px) 220px;gap:70px;padding:35px 0 70px}.eyebrow{margin:0 0 10px;color:var(--accent);font-size:.75rem;font-weight:850;letter-spacing:.1em;text-transform:uppercase}.article h1{margin:0 0 18px;font-size:clamp(2.35rem,5vw,4rem);line-height:1.03;letter-spacing:-.055em}.lead{font-size:1.13rem;color:var(--muted);margin:0 0 30px}.article h2{margin:46px 0 13px;font-size:1.65rem;line-height:1.18;letter-spacing:-.035em}.article p,.article li{color:#3f4b60}.article ul,.article ol{padding-left:23px}.note{margin:25px 0;padding:17px 19px;border-left:4px solid var(--accent);border-radius:0 10px 10px 0;background:var(--soft);color:#38425a}.code{margin:22px 0;overflow:auto;border-radius:12px;background:#171923;color:#e9edff;padding:21px;font:14px/1.75 ui-monospace,SFMono-Regular,Consolas,monospace}.task{margin-top:42px;padding:24px;border:1px solid var(--line);border-radius:14px;background:#fff}.task h2{margin-top:0}.button{display:inline-block;border-radius:9px;padding:12px 15px;background:var(--accent);color:#fff;text-decoration:none;font-weight:750}.toc{position:sticky;top:22px;height:max-content;margin-top:35px;padding-left:18px;border-left:1px solid var(--line)}.toc b{display:block;margin-bottom:9px}.toc a{display:block;color:var(--muted);text-decoration:none;font-size:.87rem;margin:7px 0}.lesson-nav{display:grid;grid-template-columns:1fr auto 1fr;align-items:center;gap:12px;margin:46px 0 0;padding-top:24px;border-top:1px solid var(--line)}.lesson-nav a{display:block;color:var(--ink);text-decoration:none;border:1px solid var(--line);border-radius:11px;padding:12px 14px;font-weight:720}.lesson-nav a:hover{border-color:var(--accent)}.lesson-nav a:last-child{text-align:right}.lesson-nav .all{text-align:center;color:var(--accent)}.playground{margin:48px 0 10px;padding:24px;border:1px solid var(--line);border-radius:16px;background:#fafaff}.playground__head{display:flex;align-items:flex-start;justify-content:space-between;gap:18px;margin-bottom:18px}.playground__head h2{margin:0 0 6px}.playground__head p{margin:0}.playground__tabs{display:flex;gap:7px;margin-bottom:10px}.playground__tab,.playground__run,.playground__reset{border:0;border-radius:8px;padding:9px 13px;font:inherit;font-weight:750;cursor:pointer}.playground__tab{background:#eceefa;color:#4b5570}.playground__tab[aria-selected="true"],.playground__run{background:var(--accent);color:#fff}.playground__reset{background:#eceefa;color:#343d52}.playground__editor{display:none;width:100%;min-height:210px;resize:vertical;border:1px solid #303346;border-radius:10px;padding:15px;background:#171923;color:#eef0ff;font:14px/1.65 ui-monospace,SFMono-Regular,Consolas,monospace}.playground__editor.is-active{display:block}.playground__actions{display:flex;gap:9px;margin:12px 0}.playground__result{width:100%;min-height:220px;border:1px solid var(--line);border-radius:10px;background:#fff}.footer{border-top:1px solid var(--line);padding:32px 0;color:#7c8798;font-size:.88rem}.footer .wrap{display:flex;justify-content:space-between;gap:20px}.footer a{color:#5a53d6}@media(max-width:760px){.top nav{display:none}.layout{display:block;padding-top:20px}.toc{display:none}.lesson-nav{grid-template-columns:1fr}.lesson-nav a,.lesson-nav a:last-child{text-align:left}.playground{padding:17px}.playground__head{display:block}.footer .wrap{display:block}.footer p{margin:10px 0}}
/* PRAKTUM-ENHANCE:START 2026-10-20 */
.meta-line{display:flex;flex-wrap:wrap;align-items:center;gap:8px 16px;margin:-12px 0 26px;color:var(--muted);font-size:.85rem}
.badge{display:inline-block;padding:3px 10px;border-radius:999px;background:#e8f7ee;color:#1d7a46;font-weight:700;font-size:.8rem}
.summary{width:100%;margin:22px 0;border-collapse:collapse;font-size:.92rem;line-height:1.5}
.summary caption{text-align:left;font-weight:800;margin-bottom:8px;color:var(--ink)}
.summary th,.summary td{padding:10px 12px;border-bottom:1px solid var(--line);text-align:left;vertical-align:top;color:#3f4b60}
.summary thead th{background:var(--soft);color:var(--ink);font-size:.8rem;text-transform:uppercase;letter-spacing:.05em}
.summary tbody th{white-space:nowrap;color:var(--ink)}
.summary--compact{max-width:340px}
.toc-inline{margin:26px 0;padding:16px 20px;border:1px solid var(--line);border-radius:14px;background:#fafaff}
.toc-inline ol{margin:8px 0 0;padding-left:20px}
.toc-inline a{color:var(--accent);text-decoration:none}
.toc-inline a:hover{text-decoration:underline}
.article h3{margin:32px 0 10px;font-size:1.22rem;letter-spacing:-.02em}
.article h2[id],.article h3[id],.task[id]{scroll-margin-top:20px}
.article code{overflow-wrap:anywhere}
.article :not(pre)>code{padding:1px 5px;border-radius:5px;background:var(--soft);font-size:.9em}
kbd{padding:1px 6px;border:1px solid var(--line);border-bottom-width:2px;border-radius:5px;font:inherit;font-size:.85em}
.faq details{border:1px solid var(--line);border-radius:12px;margin:10px 0;background:#fff}
.faq summary,.solution summary{cursor:pointer;padding:14px 18px;font-weight:700;color:var(--ink);list-style-position:inside}
.faq details p{margin:0;padding:0 18px 16px}
.faq details[open] summary{color:var(--accent)}
.solution{margin-top:14px}
.solution summary{padding:10px 0;color:var(--accent)}
.related{padding-left:20px}
.related a{color:var(--accent);font-weight:650}
@media(max-width:760px){
  .lesson-nav{grid-template-columns:auto 1fr auto;gap:8px}
  .lesson-nav:not(.lesson-nav--rich) a{padding:10px 14px}
  .lesson-nav:not(.lesson-nav--rich) a:first-child:not(.all),.lesson-nav:not(.lesson-nav--rich) a:last-child:not(.all){font-size:0;line-height:0;min-width:46px;text-align:center}
  .lesson-nav:not(.lesson-nav--rich) a:first-child:not(.all)::before{content:"←";font-size:1.15rem;line-height:1.5}
  .lesson-nav:not(.lesson-nav--rich) a:last-child:not(.all)::after{content:"→";font-size:1.15rem;line-height:1.5}
  .lesson-nav .all{text-align:center}
  .summary th,.summary td{padding:8px}
  .code{padding:16px;font-size:13px}
}
/* PRAKTUM-ENHANCE:END */
/* PRAKTUM-ENHANCE-2:START 2026-10-20 */
.summary--sizes .hsample{display:block;font-weight:800;line-height:1.15;letter-spacing:-.02em;color:var(--ink);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.summary--sizes td:nth-child(2){white-space:nowrap;color:var(--muted)}
.summary--sizes td{vertical-align:middle}
.related-cards{margin:52px 0 0}
.related-cards__head{display:flex;justify-content:space-between;align-items:baseline;gap:16px;flex-wrap:wrap}
.related-cards__head h2{margin:0 0 18px}
.related-cards__head a{color:var(--accent);text-decoration:none;font-weight:700;font-size:.92rem}
.related-cards__grid{display:grid;grid-template-columns:repeat(3,1fr);gap:16px}
.lesson-nav{margin-bottom:56px}
@media(max-width:960px){.related-cards__grid{grid-template-columns:repeat(2,1fr)}}
.rel-card{display:flex;flex-direction:column;gap:8px;padding:20px;border:1px solid var(--line);border-radius:16px;background:#fff;color:var(--ink);text-decoration:none;box-shadow:0 1px 2px rgba(23,25,35,.04);transition:border-color .15s,box-shadow .15s,transform .15s}
.rel-card:hover{border-color:var(--accent);box-shadow:0 10px 28px rgba(96,92,244,.13);transform:translateY(-2px)}
.rel-card__tag{align-self:flex-start;padding:3px 10px;border-radius:999px;background:var(--soft);color:var(--accent);font-size:.72rem;font-weight:800;letter-spacing:.06em;text-transform:uppercase}
.rel-card__title{font-size:1.12rem;line-height:1.25}
.rel-card__text{color:var(--muted);font-size:.9rem;line-height:1.5;flex:1}
.rel-card__more{color:var(--accent);font-weight:700;font-size:.9rem}
@media(max-width:760px){.lesson-nav .all{justify-self:stretch}.related-cards__grid{grid-template-columns:1fr}.rel-card{padding:16px}}
@media(prefers-reduced-motion:reduce){.rel-card{transition:none}.rel-card:hover{transform:none}}
.summary--sizes{table-layout:fixed}
.summary--sizes th:first-child{width:64px}
.summary--sizes th:nth-child(2){width:90px}
/* readability: original tracking (-.055em / -.035em) squeezed letters, esp. with system fallback fonts */
.article h1{letter-spacing:-.02em;line-height:1.08}
.article h2{letter-spacing:-.012em}
.article h3{letter-spacing:-.005em}
.summary--sizes .hsample{letter-spacing:-.01em}
/* lesson nav: buttons sized to content instead of stretched empty boxes */
.lesson-nav:not(.lesson-nav--rich) a{justify-self:center;padding:11px 18px;border-radius:999px;transition:border-color .15s,background .15s,color .15s}
.lesson-nav:not(.lesson-nav--rich) a:first-child:not(.all){justify-self:start}
.lesson-nav:not(.lesson-nav--rich) a:last-child:not(.all){justify-self:end}
.lesson-nav:not(.lesson-nav--rich) a:hover{background:var(--soft);color:var(--accent)}
.lesson-nav .all{background:var(--soft);border-color:transparent}
.lesson-nav .all:hover{background:var(--accent);color:#fff}
.lesson-nav:not(.lesson-nav--rich) a.all,.lesson-nav:not(.lesson-nav--rich) a.all:last-child{text-align:center}
/* rich lesson nav: cards with real topic titles */
.lesson-nav--rich{grid-template-columns:1fr auto 1fr;grid-template-areas:"prev all next";align-items:stretch;gap:16px}
.lesson-nav--rich .ln-card--prev{grid-area:prev}
.lesson-nav--rich .ln-card--next{grid-area:next}
.lesson-nav--rich .ln-card{display:flex;flex-direction:column;gap:6px;justify-self:stretch;padding:18px 22px;border:1px solid var(--line);border-radius:16px;background:#fff;color:var(--ink);text-decoration:none;font-weight:400;transition:border-color .15s,box-shadow .15s,transform .15s}
.lesson-nav--rich .ln-card:hover{border-color:var(--accent);background:#fff;color:var(--ink);box-shadow:0 10px 28px rgba(96,92,244,.13);transform:translateY(-2px)}
.lesson-nav--rich .ln-card--next{text-align:right;align-items:flex-end}
.lesson-nav--rich .ln-card__label{color:var(--muted);font-size:.82rem;font-weight:600}
.lesson-nav--rich .ln-card__title{font-size:1.08rem;line-height:1.3;color:var(--ink)}
.lesson-nav--rich .ln-card:hover .ln-card__title{color:var(--accent)}
.lesson-nav--rich .ln-card.ln-all{grid-area:all;align-items:center;justify-content:center;text-align:center;min-width:180px;background:var(--soft);border-color:transparent}
.lesson-nav--rich .ln-card.ln-all .ln-card__title{color:var(--accent)}
.lesson-nav--rich .ln-card.ln-all:hover{background:#fff;border-color:var(--accent)}
@media(max-width:760px){
  .lesson-nav--rich{grid-template-columns:auto 1fr auto;grid-template-areas:"prev all next";gap:8px}
  .lesson-nav--rich .ln-card.ln-all{align-items:center;text-align:center;flex-direction:row;justify-content:center;gap:8px;padding:12px 16px}
  .lesson-nav--rich .ln-card:not(.ln-all) .ln-card__title{display:none}
  .lesson-nav--rich .ln-card:not(.ln-all){min-width:52px;align-items:center!important;justify-content:center;padding:12px 16px}
  .lesson-nav--rich .ln-card:not(.ln-all) .ln-card__label{font-size:0;line-height:0}
  .lesson-nav--rich .ln-card--prev .ln-card__label::before{content:"←";font-size:1.2rem;line-height:1.4;color:var(--ink)}
  .lesson-nav--rich .ln-card--next .ln-card__label::after{content:"→";font-size:1.2rem;line-height:1.4;color:var(--ink)}
  .lesson-nav--rich .ln-card.ln-card--prev{align-items:flex-start}
  .lesson-nav--rich .ln-card,.lesson-nav--rich .ln-card:first-child,.lesson-nav--rich .ln-card:last-child{font-size:inherit;line-height:inherit;min-width:0;text-align:left;align-items:flex-start;padding:14px 16px}
  .lesson-nav--rich .ln-card.ln-card--next{text-align:right;align-items:flex-end}
  .lesson-nav--rich{align-items:stretch}
  .lesson-nav--rich .ln-card{justify-content:flex-start}
  .lesson-nav--rich a::before,.lesson-nav--rich a::after{content:none!important}
}
@media(prefers-reduced-motion:reduce){.lesson-nav--rich .ln-card{transition:none}.lesson-nav--rich .ln-card:hover{transform:none}}
/* PRAKTUM-ENHANCE-2:END */
.skip{position:absolute;left:-999px;top:10px;z-index:30;padding:10px 14px;border-radius:8px;background:#fff;color:#171923;font-weight:750;text-decoration:none;box-shadow:0 8px 24px rgba(17,24,39,.12)}.skip:focus{left:12px}.meta-line{display:flex;flex-wrap:wrap;gap:6px 18px;margin:0 0 22px;color:var(--muted);font-size:.92rem}.meta-line time{color:var(--ink);font-weight:700}.short{margin:0 0 28px;padding:18px 20px;border-radius:14px;background:var(--soft)}.short b{display:block;margin:0 0 8px}.short li{margin:4px 0}.article h3{margin:26px 0 8px;font-size:1.15rem;line-height:1.3}.article table{width:100%;border-collapse:collapse;margin:16px 0 28px;font-size:.95rem}.article caption{caption-side:top;text-align:left;font-weight:750;margin:0 0 8px;color:var(--ink)}.article th,.article td{border:1px solid var(--line);padding:9px 11px;vertical-align:top;text-align:left}.article th{background:#f6f7fb}.compare{display:grid;grid-template-columns:1fr 1fr;gap:12px;margin:18px 0 28px}.compare>div{border:1px solid var(--line);border-radius:12px;padding:14px 16px}.compare .bad{border-color:#efc2c2;background:#fff7f7}.compare .good{border-color:#bfe3cc;background:#f5fbf7}.compare p{margin:8px 0 0}.faq h3{font-size:1.08rem}.sources{padding-left:20px}.author{display:flex;gap:14px;margin:36px 0 0;padding:16px 18px;border:1px solid var(--line);border-radius:14px;background:#fff}.author b{display:block}.related{margin:10px 0 0;padding-left:20px}details.answer{margin-top:14px}details.answer summary{cursor:pointer;font-weight:750;color:var(--accent)}.article code{font-family:ui-monospace,SFMono-Regular,Consolas,monospace;font-size:.92em}@media(max-width:760px){.compare{grid-template-columns:1fr}.author{display:block}}.section-index{border-top:1px solid var(--line);padding:28px 0 12px;font-size:.95rem}.section-index__title{font-weight:750;margin:0 0 6px}.section-index h3{font-size:.85rem;text-transform:uppercase;letter-spacing:.06em;color:var(--muted);margin:18px 0 6px}.section-index ul{columns:3 210px;column-gap:28px;list-style:none;margin:0;padding:0}.section-index li{break-inside:avoid;margin:0 0 5px}.section-index a{color:var(--ink)}.section-index a[aria-current]{color:var(--accent);font-weight:700}.has-docs-nav .section-index{display:none}.article td:first-child code{white-space:nowrap}