:root{--paper:#fff;--canvas:#f6f7f8;--ink:#25282d;--muted:#666e78;--line:#e3e6e9;--accent:#ed7025;--accent-ink:#a84b14;--accent-soft:#fff3e9;--ease:cubic-bezier(.2,.7,.2,1)}
*{box-sizing:border-box}
body{margin:0;background:var(--canvas);color:var(--ink);font:14px/1.65 "PingFang SC",-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;-webkit-font-smoothing:antialiased}
button,input,select{font:inherit}button{color:inherit}button,a,summary{touch-action:manipulation}button,a,summary,select{cursor:pointer}
button:focus-visible,a:focus-visible,summary:focus-visible,input:focus-visible{outline:2px solid var(--accent);outline-offset:3px}
button:disabled{cursor:default}[hidden]{display:none!important}
.icon{display:block;width:20px;height:20px;flex:none;fill:none;stroke:currentColor;stroke-width:1.65;stroke-linecap:round;stroke-linejoin:round}
header{height:64px;padding:0 28px;background:var(--paper);border-bottom:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:32px}
.brand{display:flex;gap:12px;align-items:center;text-decoration:none;color:inherit;white-space:nowrap}.brand img{width:35px;height:35px;object-fit:contain}.brand strong{font-size:21px;letter-spacing:-.5px;font-weight:650}.brand span{font-size:12px;color:var(--muted);border-left:1px solid var(--line);margin-left:5px;padding-left:17px}
.search-wrap{position:relative;width:320px}.search-icon{position:absolute;left:14px;top:50%;transform:translateY(-50%);color:#7a828c;pointer-events:none}.search-icon .icon{width:17px;height:17px}
#search{width:100%;height:42px;border:1px solid transparent;border-radius:9px;background:var(--canvas);color:var(--ink);padding:0 14px 0 41px;font-size:13px;transition:background .18s,border-color .18s,box-shadow .18s}
#search::placeholder{color:#747c86}#search:focus{outline:none;background:#fff;border-color:#dca17a;box-shadow:0 0 0 3px #ed702510}
.search-results{position:absolute;right:0;top:calc(100% + 9px);width:420px;max-height:min(65vh,540px);overflow:auto;padding:6px;background:var(--paper);border:1px solid var(--line);border-radius:12px;box-shadow:0 14px 40px #20262d14;z-index:20}
.search-results button{display:block;width:100%;border:0;background:transparent;text-align:left;border-radius:7px;padding:11px 12px;line-height:1.6;transition:background .12s}
.search-results button:hover,.search-results button:focus-visible{background:var(--accent-soft)}.search-results button:focus-visible{outline-offset:-2px}.search-result-top{display:flex;align-items:baseline;justify-content:space-between;gap:16px}.search-result-top .time{font-size:11px;color:var(--muted);white-space:nowrap;font-variant-numeric:tabular-nums}.search-results small{display:block;color:var(--muted);font-size:11px;margin-top:2px}.search-results mark{background:transparent;color:var(--accent-ink);font-weight:600}.search-results p{padding:4px 12px;color:var(--muted);font-size:13px}
main{margin:24px 0 28px;padding:0 28px;display:grid;grid-template-columns:224px minmax(0,1fr);gap:28px}
aside{align-self:start;position:sticky;top:24px;min-width:0}aside label{display:block;font-size:12px;color:var(--muted);margin:0 0 10px;padding-left:10px}
nav{overflow:auto;scrollbar-width:thin;scrollbar-color:#cfd4da transparent;overscroll-behavior:contain;scroll-padding:8px;max-height:calc(100svh - 214px)}
nav button{display:flex;gap:11px;align-items:center;width:100%;min-height:43px;text-align:left;border:0;border-radius:7px;background:transparent;padding:10px;font-size:13px;line-height:1.6;position:relative;transition:background .14s,color .14s}
nav button:hover{background:#eaedf0}nav button[aria-current=true]{background:var(--accent-soft);color:var(--accent-ink);font-weight:600}
nav button[aria-current=true]::before{content:"";position:absolute;left:0;top:13px;bottom:13px;width:3px;border-radius:0 3px 3px 0;background:var(--accent)}
nav button:focus-visible{outline-offset:-2px}nav .number{width:19px;flex:none;font-size:11px;color:#7f8790;font-weight:400;font-variant-numeric:tabular-nums}
#categories{display:grid;gap:2px;margin:0 0 18px}#categories .icon{width:18px;height:18px;color:#737d88}#categories button[aria-current=true] .icon{color:var(--accent-ink)}#categories .category-name{flex:1}#categories .count{font-size:11px;color:#737b85;font-weight:400;font-variant-numeric:tabular-nums}#categories .chevron{display:none}
.back{display:flex;align-items:center;gap:6px;border:0;background:none;color:var(--muted);font-size:12px;padding:4px 0;margin:0 0 13px}.back .icon{width:15px;height:15px}.back:hover{color:var(--accent-ink)}
#category-title{font-size:18px;font-weight:600;margin:0 0 17px;line-height:1.4;padding-left:10px}
#lessons{margin:0 0 17px;scroll-padding-top:56px}.directory-category + .directory-category{margin-top:22px}.directory-heading{position:sticky;top:0;z-index:1;display:flex;align-items:center;gap:9px;margin:0;padding:12px 10px;background:var(--canvas);border-bottom:1px solid var(--line);font-size:14px;font-weight:600;line-height:1.5}.directory-heading .icon{width:17px;height:17px;color:var(--muted)}.directory-heading .count{margin-left:auto;color:var(--muted);font-size:11px;font-weight:400}#lessons h3{font-size:11px;font-weight:500;color:var(--muted);margin:20px 10px 7px}#lessons h3:first-child{margin-top:0}#lessons button .check{margin-left:auto;color:#75866d;font-size:12px;flex:none}
.sidebar-footer{border-top:1px solid var(--line);padding:12px 0 0;display:grid;gap:3px}
aside label.autoplay{display:flex;align-items:center;gap:9px;font-size:12px;color:var(--muted);padding:7px 10px;margin:0;cursor:pointer}
.autoplay input{appearance:none;width:28px;height:16px;flex:none;margin:0;border:0;border-radius:20px;background:#bdc4cc;position:relative;transition:background .18s}
.autoplay input::after{content:"";position:absolute;left:3px;top:3px;width:10px;height:10px;border-radius:50%;background:#fff;box-shadow:0 1px 2px #0002;transition:transform .18s var(--ease)}.autoplay input:checked{background:var(--accent)}.autoplay input:checked::after{transform:translateX(12px)}
.subtle{display:flex;align-items:center;gap:9px;border:0;background:transparent;color:var(--muted);font-size:12px;padding:8px 10px;text-align:left;border-radius:7px}.subtle:hover{background:#eaedf0;color:var(--ink)}.subtle .icon{width:16px;height:16px}
article{min-width:0}.heading{display:flex;justify-content:space-between;align-items:center;gap:16px;margin-bottom:16px}#eyebrow{font-size:12px;color:var(--muted);margin:0 0 5px}h1{font-size:28px;line-height:1.4;font-weight:600;letter-spacing:-.6px;margin:0}h1:focus{outline:none}#duration{font-size:12px;color:var(--muted);white-space:nowrap;font-variant-numeric:tabular-nums;border-left:1px solid #d8dde2;padding-left:14px}
.player-wrap{position:relative;aspect-ratio:8/5;border-radius:12px;overflow:hidden;background:#eef0f2;border:1px solid #dfe3e7;box-shadow:0 2px 5px #19242e05,0 12px 30px -18px #19242e20}video{width:100%;height:100%;display:block;object-fit:contain;background:#eef0f2}#unavailable{position:absolute;inset:0;display:grid;place-items:center;color:var(--muted);font-size:14px}
.video-meta{display:flex;justify-content:space-between;align-items:center;gap:12px;color:var(--muted);font-size:11px;padding:12px 1px}.video-meta a{display:flex;align-items:center;gap:5px;color:var(--muted);text-decoration:none}.video-meta .icon{width:14px;height:14px}.video-meta a:hover{color:var(--accent-ink)}
.steps{display:grid;grid-template-columns:repeat(auto-fit,minmax(min(225px,100%),1fr));gap:4px;border-top:1px solid var(--line);border-bottom:1px solid var(--line);padding:9px 0;margin:2px 0 16px}
.step{background:transparent;border:0;border-radius:7px;text-align:left;padding:12px 10px;line-height:1.85;font-size:12px;display:flex;gap:10px;align-items:flex-start;transition:background .14s,color .14s}.step .number{display:grid;place-items:center;width:21px;height:21px;flex:none;border-radius:6px;background:#e9ecef;color:#616b76;font-size:11px;margin-top:1px;font-variant-numeric:tabular-nums}.step:hover:not(:disabled){background:#eaedf0}.step.active{background:var(--accent-soft)}.step.active .number{background:var(--accent);color:#fff}.step:disabled{opacity:1}
details{padding:4px 0;font-size:12px}summary{display:flex;align-items:center;gap:8px;color:var(--muted);list-style:none;padding:5px 0;width:fit-content}summary::-webkit-details-marker{display:none}summary::before{content:"";width:5px;height:5px;border-right:1.5px solid currentColor;border-bottom:1.5px solid currentColor;transform:rotate(-45deg);transition:transform .14s}details[open] summary::before{transform:rotate(45deg)}summary:hover{color:var(--ink)}ul{padding-left:20px;color:var(--muted);font-size:12px;line-height:1.9;margin:9px 0 12px;max-width:76ch}li+li{margin-top:5px}
.pager{display:flex;justify-content:space-between;gap:20px;margin-top:20px}.pager button{border:1px solid var(--line);background:var(--paper);color:#505c67;border-radius:7px;padding:8px 14px;font-size:12px;transition:background .14s,border-color .14s,color .14s}.pager button:hover:not(:disabled){background:var(--accent-soft);border-color:#edc8ae;color:var(--accent-ink)}.pager button:disabled{opacity:.4}
#playback-message{color:var(--accent-ink);font-size:12px;margin:12px 0 0}
dialog{border:1px solid var(--line);border-radius:14px;padding:28px;max-width:800px;width:calc(100% - 32px);max-height:85svh;color:var(--ink);box-shadow:0 20px 80px #1113}dialog::backdrop{background:#28303955;backdrop-filter:blur(4px)}.dialog-head{display:flex;align-items:center;justify-content:space-between;gap:20px}.dialog-head h2{font-size:22px;margin:0;font-weight:600}.dialog-head button{border:0;background:var(--canvas);width:32px;height:32px;border-radius:7px;font-size:20px;color:var(--muted)}dialog>p{font-size:12px;color:var(--muted);margin:10px 0 24px}.shortcut-row{display:grid;grid-template-columns:235px 1fr;gap:24px;padding:13px 0;border-top:1px solid var(--line)}.shortcut-row b{font-size:12px;font-weight:500;line-height:1.8}.shortcut-row span{font-size:13px}.shortcut-row small{display:block;color:var(--muted);font-size:11px;margin-top:4px}
@media(min-width:801px) and (max-width:1100px){header{padding:0 24px}main{padding:0 24px;grid-template-columns:208px minmax(0,1fr);gap:28px}.brand span{display:none}.steps{grid-template-columns:1fr}.step{padding:8px 10px}}
@media(max-width:800px){header{height:66px;padding:0 20px;gap:20px}.brand span{display:none}.brand strong{font-size:18px}.brand img{width:29px;height:29px}.brand{gap:8px}.search-wrap{width:45%}#search{font-size:12px;height:38px;padding-left:34px}.search-icon{left:11px}.search-results{width:min(420px,calc(100vw - 40px))}main{display:flex;flex-direction:column;padding:0 20px;margin:22px auto 30px;gap:25px}aside{position:static;width:100%}nav{max-height:220px}#categories{grid-template-columns:repeat(2,minmax(0,1fr));gap:3px 8px;margin-bottom:12px}#categories button{min-height:43px;padding:8px;font-size:12px;gap:8px}#categories .icon{width:16px;height:16px}#categories .count{font-size:10px}#category-title{font-size:17px;margin-bottom:10px}#lessons{margin-bottom:12px}.sidebar-footer{display:flex;align-items:center;justify-content:space-between;padding-top:8px}.heading{margin-bottom:14px}h1{font-size:24px}.steps{grid-template-columns:1fr;gap:2px;padding:7px 0}.step{padding:9px 8px}.player-wrap{border-radius:9px}.shortcut-row{grid-template-columns:1fr;gap:5px}dialog{padding:22px}#eyebrow{font-size:11px}}
@media(max-width:420px){header{padding:0 16px;gap:12px}.brand strong{font-size:16px}.brand img{width:26px;height:26px}main{padding:0 16px}.search-wrap{width:46%}.search-results{width:calc(100vw - 32px)}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}

/* Website integration: retain the tutorial layout and a clear return path. */
.site-home{flex:none;white-space:nowrap;font-size:13px;color:var(--muted);text-decoration:none;padding:8px 0}
.site-home:hover{color:var(--ink)}
.site-home:focus-visible{outline:2px solid var(--accent);outline-offset:5px;border-radius:3px}
@media(max-width:800px){header{flex-wrap:wrap;height:auto;min-height:66px;padding-top:14px;padding-bottom:14px;gap:12px}.site-home{margin-left:auto;font-size:12px}.search-wrap{order:3;width:100%}main{margin-top:20px}}

/* A full-width learning workspace; the original recording is never cropped. */
header{position:sticky;top:0;z-index:10}
aside{top:88px}
.heading-actions{display:flex;align-items:center;gap:18px;flex:none}
.view-toggle{display:flex;align-items:center;gap:7px;padding:8px 11px;border:1px solid var(--line);border-radius:7px;background:var(--paper);font-size:12px;white-space:nowrap}
.view-toggle .icon{width:16px;height:16px}.view-toggle:hover{background:#eaedf0}.view-toggle[aria-pressed=true]{background:var(--ink);border-color:var(--ink);color:#fff}
.lesson-layout{display:grid;grid-template-columns:minmax(0,1fr);gap:18px}.lesson-media,.lesson-notes{min-width:0}
.player-wrap{width:min(100%,calc((100svh - 250px)*1.6));margin:0 auto;box-shadow:none;border-radius:10px}
.lesson-media{background:var(--paper);border:1px solid var(--line);border-radius:12px;padding:10px 10px 0;align-self:start}
.lesson-media .player-wrap{border:0}
.video-meta{padding:12px 4px;gap:8px;flex-wrap:wrap}
.notes-heading{display:flex;align-items:baseline;justify-content:space-between;gap:12px;margin-bottom:8px}.notes-heading h2{font-size:14px;font-weight:600;margin:0}.notes-heading>span{font-size:11px;color:var(--muted)}
.lesson-notes .steps{border-top:0;margin-top:0;padding-top:0}.lesson-notes .pager{margin-top:18px}
.directory-toggle{display:none}
@media(min-width:1440px){
 main{grid-template-columns:224px minmax(0,1fr);gap:28px}
 .lesson-layout{grid-template-columns:minmax(0,1fr) 248px;gap:24px;align-items:start}
 .lesson-notes{position:sticky;top:88px;max-height:calc(100svh - 112px);overflow:auto;scrollbar-width:thin;padding:4px 0 12px}
 .lesson-notes .steps{grid-template-columns:1fr;gap:6px;border-bottom:0;margin-bottom:12px}
 .lesson-notes .step{font-size:13px;padding:12px 10px;line-height:1.8}
 .lesson-notes details{border-top:1px solid var(--line);padding-top:12px}
 .lesson-notes .pager{gap:8px;padding-top:16px;border-top:1px solid var(--line)}
 .lesson-notes .pager button{padding:8px 12px}
}
@media(min-width:1920px){main{grid-template-columns:248px minmax(0,1fr);gap:32px;padding:0 32px}.lesson-layout{grid-template-columns:minmax(0,1fr) 280px;gap:28px}header{padding:0 32px}nav button{font-size:14px}}
@media(min-width:801px){
 body{height:100svh;overflow:hidden}
 main{height:calc(100svh - 64px);margin:0;padding-top:22px;padding-bottom:22px;min-height:0}
 aside{position:relative;top:0;height:100%;display:flex;flex-direction:column;min-height:0}
 #directory{display:flex;flex-direction:column;flex:1;min-height:0}
 #lessons{flex:1;min-height:0;max-height:none;margin-bottom:12px}
 .sidebar-footer{flex:none}
 article{overflow:auto;scrollbar-width:thin;scroll-padding-top:12px}
 .lesson-notes{top:0}
 body.focus-view main{grid-template-columns:minmax(0,1fr);padding:18px 28px 22px;margin-top:0}
 body.focus-view aside,body.focus-view .lesson-notes{display:none}
 body.focus-view .lesson-layout{grid-template-columns:minmax(0,1fr)}
 body.focus-view .lesson-media{width:fit-content;min-width:min(100%,600px);max-width:100%;justify-self:center}
 body.focus-view .player-wrap{width:min(calc(100vw - 80px),calc((100svh - 238px)*1.6))}
 body.focus-view .heading{margin-bottom:12px}
}
@media(max-width:800px){
 header{position:relative}main{gap:18px;margin-top:16px}
 aside{border:1px solid var(--line);border-radius:9px;background:var(--paper);padding:0 10px}
 .directory-toggle{display:flex;justify-content:space-between;align-items:center;width:100%;padding:12px 2px;background:transparent;border:0;font-size:13px;font-weight:600}.directory-toggle span{font-size:12px;font-weight:400;color:var(--muted)}
 #directory>label{display:none}#directory{display:none}
 aside .sidebar-footer{padding-bottom:8px}nav{max-height:min(42svh,320px)}
 .heading{gap:10px;align-items:flex-start}.heading-actions{gap:8px;padding-top:5px}#duration{border:0;padding:0;font-size:11px}h1{font-size:22px}
 .view-toggle{display:none}.player-wrap{width:100%;border-radius:6px}.lesson-media{padding:5px 5px 0;border-radius:9px}.video-meta{font-size:10px;padding:10px 4px}.lesson-layout{gap:20px}.lesson-notes .steps{grid-template-columns:1fr}
}

.catalog-entry{display:flex;align-items:center;justify-content:space-between;gap:8px;width:100%;border:0;background:none;padding:0 10px 12px;color:var(--muted);font-size:12px;text-align:left}
.catalog-entry span{font-size:11px}.catalog-entry:hover{color:var(--accent-ink)}
.catalog-dialog{width:calc(100% - 40px);max-width:780px;max-height:calc(100svh - 40px);padding:24px;background:var(--paper)}
.catalog-header{display:flex;align-items:center;justify-content:space-between;gap:20px;margin-bottom:20px}
.catalog-header h2{font-size:22px;font-weight:600;margin:0}.catalog-header>button{background:var(--canvas);border:0;width:32px;height:32px;border-radius:7px;font-size:22px;line-height:1}
.catalog-grid{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:8px}
.catalog-grid>button{display:flex;align-items:center;gap:9px;min-height:64px;text-align:left;padding:13px 12px;background:var(--canvas);border:1px solid transparent;border-radius:8px;font-size:13px;line-height:1.6}
.catalog-grid>button .icon{width:18px;height:18px;color:var(--muted)}.catalog-grid>button span{flex:1}.catalog-grid>button small{font-size:10px;white-space:nowrap;color:var(--muted)}
.catalog-grid>button:hover{border-color:#d8dde2;background:#eef0f2}.catalog-grid>button[aria-current=true]{background:var(--accent-soft);color:var(--accent-ink);border-color:#f0d4c0}
@media(max-width:600px){.catalog-dialog{padding:20px;width:calc(100% - 24px)}.catalog-grid{grid-template-columns:1fr;gap:5px}.catalog-grid>button{min-height:46px;padding:10px 12px}.catalog-header{margin-bottom:14px}.catalog-header h2{font-size:20px}}